gcc design specification - Gosford City Council - NSW Government

Gosford City Council 

GCC DESIGN SPECIFICATION 

for 

SURVEY, ROAD AND DRAINAGE WORKS 

Price: $22.00 including GST August 2008 

To Account : T0001.04 

Printed by Gosford City Council 

49 Mann Street 

Gosford NSW 2250

GCC Design Specification 

CONTENTS 

CONTENTS................................................................................................................. I 

SECTION 1................................................................................................................. 1 

INTRODUCTION ........................................................................................................ 1 

1.1 GENERAL .................................................................................................................... 1 

1.2 PROJECT BRIEF ........................................................................................................ 1 

1.3 GENERAL SPECIFICATION REQUIREMENTS.................................................. 1 

1.3.1 COPYRIGHT ......................................................................................................... 1 

1.3.2 OCCUPATIONAL HEALTH AND SAFETY ...................................................... 1 

1.3.3 TRAFFIC CONTROL............................................................................................ 2 

1.3.4 NSW GOVERNMENT CODES ............................................................................ 2 

1.4 DESIGN STANDARDS ............................................................................................... 3 

1.5 QUALITY ASSURANCE............................................................................................ 3 

SECTION 2................................................................................................................. 5 

ENGINEERING SURVEY........................................................................................... 5 

2.1 GENERAL .................................................................................................................... 5 

2.2 PERMANENT MARKS .............................................................................................. 5 

2.3 SURVEY CONTROL STATIONS ............................................................................. 5 

2.4 WORK METHODS ..................................................................................................... 5 

2.5 FEATURES TO BE LOCATED................................................................................. 6 

2.5.1 PHYSICAL FEATURES ....................................................................................... 6 

2.5.2 IMPROVEMENTS ................................................................................................ 6 

2.6 LEVELLING ................................................................................................................ 7 

2.7 EXTENT OF SURVEY................................................................................................ 7 

2.8 FORMAT REQUIREMENTS OF SURVEY DATA ................................................ 8 

2.9 INFORMATION AVAILABLE FROM COUNCIL ................................................ 8 

2.10 INFORMATION AVAILABLE FROM OTHER AUTHORITIES........................ 8 

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SECTION 3............................................................................................................... 11 

ENGINEERING DRAWINGS.................................................................................... 11 

3.1 GENERAL .................................................................................................................. 11 

3.2 PLAN SIZE................................................................................................................. 11 

3.3 DRAWING SCALES ................................................................................................. 11 

3.4 PRESENTATION GRAPHICS ................................................................................ 12 

3.5 PRINTING.................................................................................................................. 12 

3.6 VIEWS......................................................................................................................... 12 

3.7 ORIENTATION ......................................................................................................... 13 

3.8 DRAWING TITLE .................................................................................................... 13 

3.9 INFORMATION TO BE SHOWN........................................................................... 14 

3.9.1 PLAN VIEW ........................................................................................................ 14 

3.9.2 LONGITUDINAL SECTIONS............................................................................ 15 

3.9.3 CROSS SECTIONS ............................................................................................. 16 

3.9.4 CATCHMENT PLAN.......................................................................................... 17 

3.10 CHECKING OF ENGINEERING DRAWINGS.................................................... 17 

SECTION 4............................................................................................................... 19 

CONCEPT DESIGN ................................................................................................. 19 

4.1 GENERAL .................................................................................................................. 19 

4.2 CONCEPT DESIGN COMPOSITION.................................................................... 19 

4.2.1 PLAN VIEW ........................................................................................................ 19 

4.2.2 LONGITUDINAL SECTION.............................................................................. 20 

4.2.3 CROSS SECTION ............................................................................................... 20 

4.2.4 CONCEPT REPORT ........................................................................................... 20 

SECTION 5............................................................................................................... 21 

ROAD DESIGN ........................................................................................................ 21 

5.1 GENERAL .................................................................................................................. 21 

5.2 DESIGN STANDARDS ............................................................................................. 21 

5.4 TYPICAL CROSS SECTIONS ................................................................................ 22 

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5.5 WIDTH OF FOOTWAY........................................................................................... 23 

5.6 DESIGN SPEED......................................................................................................... 23 

5.7 HORIZONTAL ALIGNMENT ................................................................................ 23 

5.8 CROSSFALLS AND SUPER-ELEVATION........................................................... 23 

5.9 TRANSITIONS AND WIDENING ON CURVES.................................................. 24 

5.10 LONGITUDINAL GRADING.................................................................................. 24 

5.11 SIGHT DISTANCE.................................................................................................... 25 

5.12 VERTICAL CURVES ............................................................................................... 25 

5.13 BATTERS ................................................................................................................... 26 

5.14 PROPERTY DRAINAGE ......................................................................................... 27 

5.15 SUBSOIL DRAINS .................................................................................................... 28 

5.16 KERB AND GUTTER ............................................................................................... 28 

5.17 KERB RAMPS ........................................................................................................... 29 

5.17 FOOTWAY CROSSINGS - VEHICULAR ACCESS ............................................ 31 

5.18 INTERSECTIONS ..................................................................................................... 31 

5.20 CUL-DE-SAC AND HAMMER HEAD FACILITIES........................................... 32 

5.21 TRAFFIC CONTROL DEVICES ............................................................................ 33 

5.22 FOOTPATHS ............................................................................................................. 33 

5.23 CYCLEWAYS............................................................................................................ 33 

5.24 EROSION AND SEDIMENTATION CONTROL ................................................. 34 

5.25 PROPERTY ADJUSTMENT ................................................................................... 34 

5.26 PHOTOGRAPHIC RECORDS ................................................................................ 34 

5.27 LANDSCAPING......................................................................................................... 34 

5.28 PUBLIC UTILITIES ................................................................................................. 35 

5.29 ROADLOC REFERENCES...................................................................................... 35 

5.30 SURVEY MARKS...................................................................................................... 35 

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5.31 DESIGN REPORT..................................................................................................... 36 

5.32 PAVEMENT DESIGN............................................................................................... 36 

SECTION 6............................................................................................................... 39 

STORMWATER DRAINAGE DESIGN..................................................................... 39 

6.1 GENERAL .................................................................................................................. 39 

6.2 DESIGN STANDARDS ............................................................................................. 40 

6.3 HYDROLOGY ........................................................................................................... 40 

6.3.1 Design Rainfall Data ............................................................................................ 40 

6.3.2 Catchment Area.................................................................................................... 42 

6.3.3 Hydrological Models............................................................................................ 43 

6.3.3.1 Rational Method.............................................................................................. 43 

6.4 HYDRAULICS ........................................................................................................... 46 

6.4.1 Hydraulic Grade Line........................................................................................... 46 

6.4.2 Gutter flow ........................................................................................................... 47 

6.4.3 Culverts ................................................................................................................ 47 

6.4.4 Pits........................................................................................................................ 47 

6.4.5 Hydraulic Losses.................................................................................................. 48 

6.5 OVERLAND FLOW PATHS.................................................................................... 50 

6.5.1 General ................................................................................................................. 50 

6.5.2 Freeboard.............................................................................................................. 50 

6.6 OPEN CHANNELS.................................................................................................... 52 

6.7 MAJOR STRUCTURES ........................................................................................... 53 

6.8 RETARDING BASINS .............................................................................................. 54 

6.9 ON-SITE STORMWATER DETENTION.............................................................. 55 

6.10 INTERALLOTMENT DRAINAGE......................................................................... 56 

6.10.1 Interallotment Drainage Pits ................................................................................ 57 

6.11 CONDUITS, LOCATION AND COVER................................................................ 58 

6.12 EASEMENTS ............................................................................................................. 58 

6.12.1 Easement Widths.................................................................................................. 58 

6.12.2 Building Adjacent to Easements ...................................................................... 60 

6.13 STORMWATER DISCHARGE............................................................................... 61 

6.14 MISCELLANEOUS................................................................................................... 62 

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6.14.1 Trench stops and Bulkheads............................................................................. 62 

6.14.2 Subsoil Drainage .............................................................................................. 62 

6.14.3 Kerb and Gutter Discharge............................................................................... 62 

6.14.4 Habitable Floor Levels..................................................................................... 62 

6.15 DOCUMENTATION ................................................................................................. 63 

6.15.1 Easements and Agreements.............................................................................. 63 

6.16 STORMWATER QUALITY..................................................................................... 63 

6.17 MAINTENANCE PLAN ........................................................................................... 64 

Appendix A ............................................................................................................................. 66 

STANDARD LINE TYPES AND SYMBOLS ................................................................... 66 

Appendix B.............................................................................................................................. 67 

STORMWATER DRAINAGE CALCULATION FORM .................................................. 67 

Appendix C ............................................................................................................................. 68 

ACCESS PROFILE ABOVE ROAD................................................................................... 68 

FOR RTA STANDARD CAR 130MM CLEARANCE ...................................................... 68 

ACCESS PROFILE BELOW ROAD .................................................................................. 69 

FOR RTA STANDARD CAR 130MM CLEARANCE ...................................................... 69 

MAXIMUM ACCESS PROFILE FOR NEW SUBDIVISIONS ........................................ 70 

Appendix D ............................................................................................................................. 71 

TIME OF FLOW IN GUTTER............................................................................................ 71 

Appendix E.............................................................................................................................. 72 

Figure E1- RAINFALL INTENSITY ZONES .................................................................... 72 

Figure E2 - URBAN COEFFICIENT OF RUNOFF C10 .................................................... 73 

TABLE E1 - RAINFALL INTENSITY (mm/hr) FOR TERRIGAL................................... 74 

TABLE E2 - RAINFALL INTENSITY (mm/hr) FOR WOY WOY................................... 75 

TABLE E3 - RAINFALL INTENSITY (mm/hr) FOR MANGROVE CREEK DAM ....... 76 

TABLE E4 - RAINFALL INTENSITY (mm/hr) FOR PEATS RIDGE ............................. 77 

TABLE E5 - RAINFALL INTENSITY (mm/hr) FOR NARARA...................................... 78 

TABLE E6 - RAINFALL INTENSITY – DURATION RETURN PERIOD FOR TERRIGAL .............. 79 

TABLE E7 - RAINFALL INTENSITY – DURATION – RETURN PERIOD FOR WOY WOY ........... 80 

TABLE E8 –......................................................................................................................... 81 

RAINFALL INTENSITY – DURATION – RETURN PERIOD FOR MANGROVE CREEK DAM.......... 81 

TABLE E9 - RAINFALL INTENSITY – DURATION – RETURN PERIOD FOR PEATS RIDGE....... 82 

TABLE E10 - RAINFALL INTENSITY – DURATION – RETURN PERIOD FOR NARARA............ 83 

TABLE E11 - RAINFALL DURATION INTENSITY (min mm/hr) FOR TERRIGAL (t.I 0.4 ) .............. 84 

TABLE E12 - RAINFALL DURATION INTENSITY (min mm/hr) FOR WOY WOY (t.I 0.4 )............... 85 

TABLE E13 – ....................................................................................................................... 86 

RAINFALL DURATION INTENSITY (min mm/hr) FOR MANGROVE CREEK DAM (t.I 0.4 )................. 86 

TABLE E14 - RAINFALL DURATION INTENSITY (min mm/hr) FOR PEATS RIDGE (t.I 0.4 ) ............ 87 

TABLE E15 - RAINFALL DURATION INTENSITY (min mm/hr) FOR NARARA (t.I 0.4 ) ................. 88 

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Appendix F.............................................................................................................................. 89 

MAXIMUM PERMISSIBLE GUTTER FLOW.................................................................. 89 

Appendix G ............................................................................................................................. 90 

KERB INLET CAPACITY.................................................................................................. 90 

Appendix H ............................................................................................................................. 91 

PRESSURE HEAD CHANGE COEFFICIENTS “ K “ DIAGRAMS................................ 91 

Appendix I............................................................................................................................... 99 

VELOCITY AND DISHARGE DIAGRAM ....................................................................... 99 

Appendix J ............................................................................................................................ 100 

MINIMUM HGL OUTLET CONTROL LEVEL (AHD) ................................................. 100 

Appendix K ........................................................................................................................... 101 

PERCENTAGE IMPERVIOUS FOR VARIOUS ZONING AREAS............................... 101 

Appendix L............................................................................................................................ 102 

VOLUME AND DEPTH RELATIONSHIPS ................................................................... 102 

Appendix M .......................................................................................................................... 103 

INTERALLOTMENT PIT SCHEDULE........................................................................... 103 

Appendix N ........................................................................................................................... 104 

STANDARDS AND GUIDELINES.................................................................................. 104 

Appendix O ........................................................................................................................... 107 

STORMWATER DRAINAGE CALCULATION FORM DETAILS............................... 107 

vi Version 4 (August 2008)


SECTION 1 

INTRODUCTION 

1.1 GENERAL 

This is the second edition of Gosford Council’s Design Specification. The document has 

been prepared as a guide for the procedures to be followed in the survey and design of 

road works and stormwater drainage by staff of Gosford City Council and Consultants 

engaged by Council to design Council projects. 

This document may be used as a guide to developers for the design of road and 

stormwater drainage works required by Development Consent. All reference to the 

“Project Manager” is for Council projects only. All enquires regarding design standards 

for development consent is to be directed to the relevant Development Assessment team 

within Council. 

A new Section 4 has been included to cover the investigation of candidate proposals up 

to the concept design phase, while Section 5 proceeds to the detailed design of the 

approved project. 

In the preparation of a design, liaison must be maintained between the Consultant and 

the Gosford Council officer or Project Manager responsible for the project (hereafter 

called the "Project Manager"). 

1.2 PROJECT BRIEF 

For each Council project, a brief will be prepared by Council to detail the extent and 

timing of all work under the project, and will also include any special requirements that 

add to or supersede aspects of this General Specification. 

1.3 GENERAL SPECIFICATION REQUIREMENTS 

For each Council project, the following requirements are common to all areas of activity 

in Sections 2 to 6 and must be taken into account by the Consultant: 

1.3.1 COPYRIGHT 

All data collected during surveys will remain the property of Gosford City Council and 

cannot be used for other purposes unless specific permission has been obtained. 

1.3.2 OCCUPATIONAL HEALTH AND SAFETY 

The Contractor shall comply with the NSW Occupational Health and Safety Act, 2001 

and the requirements of Council’s OHS&R policy. 

Each member of the consultants team that is required to be on the project site shall have 

undertaken both the Gosford City Council OHS&R induction training and the Work Cover 

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General Construction Induction Certificate. Copies of both induction certificates are to be 

provided to the Project Manager prior to commencement of work. 

The consultant shall ensure a Risk Assessment, related to the work they are about to 

undertake, is conducted and determine the level risk for each area and task. The 

consultants must supply details of safe work methods and other proposed means of 

complying with Council's requirements prior to commencing work. 

The consultants are to provide their own personal protective equipment and clothing in 

accordance with AS1742.3 and as agreed by Council. 

The consultants shall comply with relevant standard operating procedures and safe 

working practices. 

Council will monitor the consultant’s compliance with Occupational Health & Safety 

policies, standard operating procedures and safe working practices. The consultant shall 

immediately address any non-conformances identified. Details of safety breaches and 

attitudes towards workplace safety will be documented and considered in the allocation 

of future work. 

1.3.3 TRAFFIC CONTROL 

Traffic control during all field survey works shall be in accordance with: 

* RTA ‘s Traffic Control at Work Sites Manual, Issued December 1998, and 

* Australian Standard 1742.3 – 2002 Traffic Control Devices for Works on Roads. 

The consultant shall not park a vehicle on the through traffic lanes unless protected by a 

lane closure detailed in accordance with AS1742.3. All consultant personnel while on 

site shall wear fluorescent safety vests in accordance with AS1742.3. 

Where traffic controllers are required to control traffic around the survey area, the 

consultant shall advise the Project Manager of their names with a signed declaration that 

they are properly trained in the duties of traffic controllers in accordance with AS1742.3. 

In addition to the requirements of AS1742.3, a traffic controller shall remain at the head 

of each traffic queue while it is halted. 

1.3.4 NSW GOVERNMENT CODES 

All consultants must comply with the NSW Government Code of Practice for the 

Construction Industry and Councils Purchasing Policy. Submission of a quotation will be 

evidence of the consultant agreement to comply with these requirements for the duration 

of any project that may be awarded. If any consultants fail to comply with these 

requirements, the failure may be taken into account by Council when considering this or 

any subsequent quotation by the consultants and may result in this or any subsequent 

quotation being passed over. 



1.4 DESIGN STANDARDS 

This Specification is to be read in conjunction with the Standards and Guidelines listed in 

Appendix N and may be varied by the Brief. The following order of precedence applies in 

the design standards to be adopted:- 

1 Specific provisions in the Project Brief 

2 RTA publications 

3 NAASRA / AUSTROADS publications 

4 Australian Standards, and 

5 Other publications 

1.5 QUALITY ASSURANCE 

Council is a quality assurance facilitator and may require the inclusion of quality 

assurance proposals as a requirement of the design process. 



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SECTION 2 

ENGINEERING SURVEY 

2.1 GENERAL 

The engineering survey shall be carried out by a suitable qualified engineering surveyor 

using the ISG co-ordinate reference system and Australian Height Datum (AHD). The 

survey is to accurately show the landform to facilitate the best possible design and 

construction of roadworks and drainage consistent with minimum interference to the 

existing amenity of the area. 

Gosford City Council is committed to the implementation of the new Map Grid of Australia 

(MGA) coordinate reference system where possible. 

2.2 PERMANENT MARKS 

All information relating to Permanent Marks (PM) and State Survey Marks (SSM) is to be 

obtained by the Consultant from the Survey Control Information Management System 

(SCIM) prior to the commencement of the site survey. 

The Permanent Mark used to derive levels for the project is to be noted on the design 

plans. 

2.3 SURVEY CONTROL STATIONS 

At least two survey control stations within the sight of each other shall be established at 

each project site by the engineering surveyor clear of any proposed works at a maximum 

spacing of 200 metres. 

Care should be exercised in locating the survey control stations so that they can be used 

during the whole of construction and not for example on the high side of a road where 

there is likely to be a large cutting and the mark lost during construction. 

The survey control stations must be of a durable nature such as a bolt, a GI pipe, nail in 

a dumpy peg, nail in the bitumen or a drill hole and wing in concrete. 

The survey control stations shall be painted white and numbered for ease of location in 

the field by others. 

2.4 WORK METHODS 

Work methods employed should be self checking with redundant/check, observations/ 

measurements made between set out points and adjacent/ related, structures to confirm 

the integrity of the set out and the drawing dimensions. 

The set out equipment, techniques, frequency, type and location of survey points shall 

take into account the specific tolerances of the construction element, the design function 

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of the construction and the construction techniques proposed. 

2.5 FEATURES TO BE LOCATED 

All relevant physical features and improvements shall be accurately located for plotting 

on the engineering drawings, as follows: 

2.5.1 PHYSICAL FEATURES 

Any features, which may be affect by construction, are to be located by the Surveyor. 

These include changes in grade, rock outcrops, cliffs, caves, watercourses, ponds and 

the like. All trees (greater than 3 metres in height) within the road reserve and those 

within three metres either side of a proposed drainage line together with any others likely 

to be affected by the works, must be located and shown on the plan. 

Reference shall be made to the following council policies 

“Landscape and Vegetation Management Policy” R6.03. 

“Draft Development Control Plan No 140”. 

“Register Of Significant Trees”. 

Council’s Tree Management Officer is to be contacted prior to any clearing or under 

scrubbing being carried out. 

Small watercourses that run only in times of rain may be shown as a single line but 

streams and creeks should have a full cross section of the creek located at 10m intervals 

and at changes in direction and width. 

2.5.2 IMPROVEMENTS 

Improvements that are to be located in plan view by the Surveyor include any man made 

structures and utility services such as roads, kerb and gutter, drains and drainage 

structures, fences, buildings, vehicle entrances, driveways, water and sewerage mains, 

manholes and valves, telecommunication cables and pits, underground electricity cables, 

gas mains and overhead power and telephone poles and the like. 

It is the responsibility of the consultant to contact all relevant authorities to obtain current 

locality plans and to arrange location; excavation and leveling of all utilities which crossproposed 

drainage lines or could affect design levels. The sewer main work as executed 

drawing may be used to identify sewer lines for the design. 

The consultant is required to excavate and confirm the level of sewer mains within 

300mm of any proposed drainage pipeline. The locations of sewer junctions are to be 

shown on the plan view and checked for conflict with the proposed drainage system. 

All utilities must be accurately located in the field and shown clearly on the plan and 

drainage longitudinal sections. 

If a utility service is unable to be located at the time of design and interpolation is 

necessary, then approval is to be obtained from Council before including the detail on the 

design plans and clearly high lighting that the utility level is assumed. 

A copy of all utility diagrams collected is to be supplied to Council with the submission of 

6 



the survey plan. 

2.6 LEVELLING 

All levels must be related to Australian Height Datum (AHD). 

The datum must be verified by closed height difference between two benchmarks with 

known AHD levels. The benchmarks used to derive levels for the project is to be noted 

on the design plans. 

All height differences are to attain a precision of 0.012√km metres or better (km is the 

length of level run in kilometres, the result is expressed in metres). 

The Reduced Level (R.L) of control stations is to be obtained by differential levelling. 

Copies of closed level runs are to be kept by the surveyor and made available to Council 

on request. Field notes may be called upon to check the difference between R.L’s and 

levels obtained by electronic means. 

2.7 EXTENT OF SURVEY 

Sufficient survey data is to be collected by the Surveyor, with particular attention being 

given to the location of trees, utility services, access crossings, water courses, changes 

in grade and property improvements adjacent to and within the area being surveyed. As 

a minimum the full width of the road reserve plus 5m each side is to be surveyed. 

The Surveyor shall supply survey information at a maximum 10 metre spacing to allow 

the development of an accurate digital terrain model (DTM) for the extraction of 

longitudinal and cross sections. 

The DTM should be verified and for existing road pavements and associated structures 

shall be within ± 15mm of the actual R.L at any point, unless otherwise specified. 

All driveways are to be surveyed in sufficient detail to identify the extent of property 

adjustments required. The survey shall locate both edges of the driveway and extend at 

least 5m into the property and locate and level any garage floor.. 

Survey shall extend for at least 60 metres past the design area and along side roads to 

enable longitudinal and cross section to be developed. Where Council considers cross 

sections are unnecessary to determine tie-in works then only centreline levels for 60 

metres past the design area shall be provided to enable a longitudinal section to be 

developed to define tie-in works. 

The spacings specified above are to be regarded as a maximum and where necessary, 

extra survey should be provided at sudden changes of grade to enable earthwork 

quantities to be calculated with reasonable accuracy. 

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2.8 FORMAT REQUIREMENTS OF SURVEY DATA 

All survey data shall be submitted on a suitable formate for use in Council’s computers. 

The Consultant shall supply output data in Civilcad software format, using Council’s 

approved symbols and line types. Refer to Appendix A 

Upon receipt of the survey the consultant shall supply Council with the following: 

1. Electronic storage device containing 

- survey data output: (point numbers R.L’s and codes) 

- Digital Terrain Model (DTM) 

- Cadastral information 

- Reference marks and traverse stations used for the project 

2. Detailed plan showing all survey topographical features, survey points 

with level, codes and contours at 0.5 metre intervals. In flat areas or water 

courses and flood plains 0.2 metre intervals shall be provided. 

2.9 INFORMATION AVAILABLE FROM COUNCIL 

It shall be the responsibility of the Consultant to obtain any or all of the following 

information from Council. 

• Indicative locations only of water reticulation mains and trunk water mains 

• Sewer mains and rising mains in the form of work as executed drawing. 

• DXF file of the site drainage catchment showing boundaries. Contours and existing 

drainage structures. ( Council projects only ) 

• 1% Flood levels and extents. 

• Approximate location of existing storm water drainage culverts. 

2.10 INFORMATION AVAILABLE FROM OTHER AUTHORITIES 

It shall be the responsibility of the Consultant to obtain any or all of the following 

information: 

• Boundary information 

- Deposited Plans from the Land Title Office 

- Easements from the Certificate of Title 

- Covenants from the Certificate of Title 

• Road widening which may impact on the survey site, information from Council or 

RTA. 

• Location and level of PM’s and SSM’s from SCIMS 

Phone 02 92674988 Fax No 02 92674942 

www.lic.gov.au 

8 



• Electricity from Energy Australia or Dial Before You Dig on Ph 1100 

• Telecommunications from Dial Before You Dig on Telephone: 1100 

- Telstra 

- Optus 

- Optic Fibre 

• Gas from Australian Gas and Lighting AGL or Dial Before You Dig on Telephone: 

1100 

9 




10 



SECTION 3 

ENGINEERING DRAWINGS 

3.1 GENERAL 

All engineering drawings should comply with the following guidelines in order to 

standardise the plans prepared. A standard presentation has many obvious advantages 

in the design and construction process, and departures from the guidelines should only 

be contemplated when adherence to the guidelines would actually fail to convey all the 

necessary information. The Project Manager prior to their adoption should approve all 

such departures from the guidelines. 

3.2 PLAN SIZE 

Plans are to be supplied on A series ISO standard sheet sizes (A0, A1, A3, A4 etc). 

As a general rule all Council projects shall have final designs provided as one set of A1 

film and one set of A3 paper copies 

Conceptual plans may utilise up to 914 mm wide continuous length sheets if appropriate. 

An approved CAD system is to be used for design and drafting of all design project. Ink 

on lightweight paper plots will be acceptable for Preliminary and Draft drawing stages. All 

Council design projects are to be presented on Council's standard drawing sheet. An 

AutoCad drawing file can be made available. 

CAD files of the project final drawings are to be provided in AutoCad format. 

All CAD files and drawing produced as part of the project become the property of 

Gosford City Council and copies of the drawings may not be taken without prior Council 

approval 

3.3 DRAWING SCALES 

The appropriate scale should be selected to ensure clarity of the drawing information and 

shall generally be adopted as follows: 

VIEW A1 size A3 size 

Plan View: 1:250 1:500 

Longitudinal Section: 1:250 horizontal 1:500 horizontal 

1:50 vertical 1:100 vertical 

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VIEW A1 size A3 size 

Cross Sections 1:100 natural 1:200 natural 

Typical Cross-sections 1:100 natural 1:200 natural 

Structures - Pits etc 1:20 1:40 

Inset details 1:20 1:40 

Locality Sketch 

as per UBD scale 

Stormwater Drainage 1:250 horizontal 1:500 horizontal 

1:50 vertical 1:100 vertical 

Bar Scales are to be provided on all sheets with the original sheet size shown to assist 

with reduced plan scaling ie. 1:250 A1 

3.4 PRESENTATION GRAPHICS 

Council’s standards for Civilcad Line types, symbols and font types will be provided and 

shall be used by the Consultant. 

3.5 PRINTING 

The minimum size of any lettering or numbering shall be 3mm for A1 sheet and 1.5mm of 

A3 sheets. All annotation shall be carried out using CAD systems unless otherwise 

approved. 

Hand tracing, stencils or scribers will not be accepted. 

3.6 VIEWS 

Detailed drawings are to be uncluttered and information clearly defined. The detailed 

design product shall be fully prepared by electronic means without manual enhancement. 

Roadworks require: 

a 

b 

c 

d 

e 

f 

g 

h 

I 

Plan 

Longitudinal section along road centre line 

Cross sections (including typical) 

Kerb return profiles 

Specialised detail (including slip roads, special access, property 

adjustments, etc) 

Longitudinal sections for stormwater drainage pipelines 

Sedimentation Control details 

Signposting and line marking 

Landscaping Plan 

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Stormwater drainage requires: 

a 

b 

c 

d 

e 

f 

g 

h 

i 

j 

Sheet index 

Plan 

Longitudinal section 

Cross sections at 15 metre intervals or at critical locations (for major open 

channels only) 

Set out sheet 

Hydrology and hydraulic calculation tables 

Sedimentation Control details 

Scaled catchment plan 

Special pit details 

Structural details 

3.7 ORIENTATION 

3.7.1 ROADWORKS 

Alignment shall not to be based on compass direction. Drawing orientation and direction 

of chainages must be in accordance with the RTA ROADLOC system. Chainages must 

also be in ascending order from left to right across the sheet. 

3.7.2 STORMWATER DRAINAGE 

Drainage shall generally be in accordance with the Roadworks Plans, with the 

longitudinal section aligned such that the outlet end of the drainage line is to the left of 

the drawing sheet. 

3.8 DRAWING TITLE 

Street name, section of street and minimal description of work are to be included in the 

Title. 

Council’s Project Supervisor will supply the project file number and plan number for 

insertion in the title block. 

For development consent plans, the DA number together with the lot, DP, land 

description and development type are to be shown in the title block. 

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3.9 INFORMATION TO BE SHOWN 

3.9.1 PLAN VIEW 

All relevant design information and topographical features must be shown and shall 

include but not limited to: 

‣ Title block, legend, north point, scale and scale bar. 

‣ Locality sketch 

‣ Survey control marks with location, description, reduced level and co-ordinate. 

Marks shall be established clear of any works at a maximum spacing of 

200 metres with a minimum of two per project. 

‣ The permanent mark used to derive levels for the project is to be noted on the 

plans. The deposited plan number used to relate boundary information to the 

coordinate system is to be noted on the plans. 

‣ Design centre line chainages, TPs, IPs and bearings along straights 

‣ Details of proposed subsoil drainage lines. 

‣ Property boundaries, easements, rights-of-carriageway, lot numbers, deposited 

plan numbers and house numbers. 

‣ Road names and Main Road numbers if applicable. 

‣ Proposed kerb and gutter alignment. 

‣ Where minor adjustment or extensions to drainage structures is proposed, a note 

detailing the proposed work and the pit/bend hydraulic information may be 

considered adequate. A drainage longitudinal section would therefore be 

unnecessary. 

‣ The location of proposed drainage structures with pit or bend numbers 

corresponding with those shown on the stormwater catchment plan and drainage 

longitudinal sections. 

‣ Construction notes relating to adjustments of accesses, public utilities or other 

physical features or improvements. 

‣ Limit of construction defined 

‣ The extent of access adjustment is to be shown as a hatched area on the plan. 

‣ Sedimentation control details where a separate plan is not required. 

‣ Service location “Dug” symbol to identify underground service location point. 

‣ Extent of 1% AEP flood plain. 

Only relevant physical features and improvements should be shown. 

However, the following details must be shown: 

‣ Existing drainage structures including culvert sizes, top and toe of open channels. 

‣ Existing edges of the bitumen or gravel road surface. 

‣ All access crossing locations, approximate width and surface material type. 

‣ Existing kerb and gutter. 

‣ All public utilities, including the location of: 

- Telecommunication conduits, junction cables, riser plant, pits, 

manholes and poles. 

- Energy Australia electricity poles, underground conduits and 

14 



cables, stays, anchors, pole transformers and kiosk transformers. 

- Sewer reticulation mains, rising mains, pumping stations, 

manholes, lamp holes and relevant house junction locations. 

- Water mains, including size and material type, location of bends, 

tees, hydrants, stop valves, thrust blocks, etc. 

- Gas mains, location of bends, tees and fitting. 

Dimension and/or co-ordinates for all work to be carried out so that it may be set out and 

constructed without the need for scaling from the plan or for field assumptions. 

3.9.2 LONGITUDINAL SECTIONS 

3.9.2.1 ROADWORKS 

The details to be shown should include: 

a Title block, scales and scales bar 

b Chainage 

c Existing level on pegged centreline 

d Design level on proposed centreline 

e Vertical alignment of proposed centreline include chainages, RLs, grades 

and intersection points 

f Datum RL of longitudinal section 

g Limit of construction. 

h Street intersection names and chainage 

i Low points and high points along the design centreline 

j chainage, size and level of public utility mains affecting the work. 

k chainage, size and level of drainage structures affecting the work. 

3.9.1.2 STORMWATER DRAINAGE 

The details to be shown will vary depending upon the location of the pipeline but 

should generally include: 

a 

b 

c 

d 

e 

f 

g 

h 

i 

j 

k 

l 

m 

n 

Title block, scales and scales bar 

Chainage 

Pipe/drain invert level 

Existing surface level (also existing drain bed level if applicable) 

Finished surface level (may alternatively be described as future kerb level 

if in a street) 

Culvert size, length, grade and class 

Datum RL of longitudinal section 

Hydraulic grade line levels at each pit and headwalls 

Design flow and recurrence interval 

Pipe full velocity 

Minimum friction grade of the design culvert 

Utility crossing location, level and size 

Structure reference number and description ie. Inlet Pit, Headwall ect. 

1% AEP flood levels 

The design consultant shall undertake all survey, investigation, excavation and 

inspection necessary to obtain the required utility location. For Council projects utility 

location works will be undertaken as a variation to the project cost. Any such 

15 



excavations must be backfilled and left in a safe condition. Excavations within road 

pavements are to be compacted and restored with road base and asphalt seal. 

The hydraulic grade line (HGL) of the pipe and pit network shall also be plotted on the 

drainage longitudinal section. Where the HGL calculated is below the pipe obvert level 

the upstream pressure head change (Hp) shall be measured from the outlet pipe obvert 

level. At the downstream end of the pipeline network the HGL shall commence at the 

highest level of either 

a 

b 

c 

the pipe obvert level 

the minimum HGL outlet control level specified in Appendix J 

the water surface level in the outlet channel resulting from the design 

storm event. 

3.9.3 CROSS SECTIONS 

3.9.3.1 ROAD CROSS SECTIONS 

The following information shall be shown: 

a 

b 

c 

d 

e 

f 

G 


Chainage below each section 

Existing surface RL 

Design surface RL 

Batter slopes (ratio) 

Typical cross section details, with pavement details and sub soil drainage. 

Sections shall be full width of road reserve, access handle or right of way. 

3.9.3.2 DRAINAGE CROSS SECTIONS 

The following information shall be shown: 

a 

b 

c 

d 

e 

f 

g 


Chainage below each section 

Existing surface RL 

Design surface RL 

Design water surface RL 

Batter slopes (ratio) 

Typical cross section details 

16 



3.9.4 CATCHMENT PLAN 

The plan is to include the project catchment area showing the following details: 

a 

b 

c 

d 

e 

f 

line diagram of drainage system 

pit reference numbers and area 

sub-catchment boundaries 

contours 

property boundaries 

scale 

For Council projects a DXF file of the project drainage catchment area showing 

boundaries, contours and existing drainage structures will be provided. 

3.10 CHECKING OF ENGINEERING DRAWINGS 

The Project Manager will carry out an initial check of drawings and catchment 

calculations. All aspects of the design including levels, grades and details will be 

checked. Only after final approval of both the engineering drawings and catchment 

calculations by the Project Manager shall the Consultant's design be considered 

complete. 

17 




18 



SECTION 4 

CONCEPT DESIGN 

(Council Projects only) 

4.1 GENERAL 

It is particularly important to assess various options associated with a design prior to 

committing the design to one specific proposal. 

Concept design in this Specification refers to the following stages: 

(i) 

(ii) 

(iii) 

formulating broad objectives for the project 

developing viable conceptual options, and 

selecting the preferred option. 

4.2 CONCEPT DESIGN COMPOSITION 

This includes the development, presentation of concept alternatives together with 

supporting documentation as required by the Brief. 

Methods may vary for the adoption of - 

 

 

 

 

Option Selection 

Option Definition 

Option Analysis 

Evaluation 

Those adopted for any particular project should be selected bearing in mind the 

requirements of the project brief. 

This applies especially to the level of work required in traffic survey, economic analysis, 

community consultation and cadastral data collection. 

4.2.1 PLAN VIEW 

The layout should enable comprehensive interpretation and discussion to be held with 

Council’s Project Team, the RTA (if appropriate) and the community. It should show 

general arrangement of existing and proposed work and include - 

 

 

 

 

 

 

Extent of work 

Pavement marking 

Dimensions 

Property boundaries 

Existing utilities, and 

Major structures 

19 



4.2.2 LONGITUDINAL SECTION 

These should be provided where appropriate to show outline of existing and proposed 

vertical alignment and include - 

 

 

 

 

grades 

vertical curve lengths 

horizontal alignment, and 

major structures 

4.2.3 CROSS SECTION 

Sections should be provided at typical and critical locations and include dimensions and 

property boundaries. 

4.2.4 CONCEPT REPORT 

The objective of a concept report is to present Council’s Project Team with the 

information, options and recommendations required to make a sound decision on - 

 

 

whether to proceed with the implementation of a proposed project, and 

what form the project should take. 

The report will complement the concept drawing and provide justification for all critical 

decisions taken in developing the preferred concept. 

The concept report is to recommend a preferred option for adoption. The reasons for 

choosing the preferred option over other options are to be clearly stated. 

20 



SECTION 5 

ROAD DESIGN 

5.1 GENERAL 

This section outlines minimum standards for the design of roads, footpaths and 

associated treatments. Every effort should be made to achieve these standards where 

economically and practically feasible. 

Where it is impracticable to obtain the requirements set out hereafter, the design controls 

should be discussed with the Project Manager. The Project Manager prior to their 

adoption must approve variations from these standards. 

Each case for variation from the design standards shall be submitted for approval 

separately. 


Road design standards are defined in Appendix N of this Specification 

5.3 CARRIAGEWAY WIDTH 

The carriageway, footpaths and road reserve width for new subdivisions are defined in 

Council’s Development Control Plans No. 112 Residential Subdivisions and No. 130 

Subdivision of Rural and Non-Urban Land and are generally established as part of the 

Development Consent. 

For Council design projects the width of carriageway shall be as specified in the design 

brief. 

Isolated minor reductions (up to 0.4 metres) in the carriageway width to avoid the need 

for relocating a major physical constraint may be tolerated. The Project Manager must 

be consulted before any such variations are included. 

Provision shall be made for cycleway use in all road designs. The widths specified in the 

design brief will include this provision. 

21 



5.4 TYPICAL CROSS SECTIONS 

The typical road cross section shall be that detailed below. 

Table drains shall be concrete lined where the longitudinal grade is steeper than 5%. 

22 



5.5 WIDTH OF FOOTWAY 

(Urban Roads Only) 

The minimum width of footway shall be 3.5m to provide for utilities and a footpath area. 

In steep areas where the depth of cutting or embankment is consistently greater than 2.0 

metres Council may give consideration to a reduction in the width of footway formation in 

urban areas to a minimum of 2.0 metres to allow for the provision of a footpath and grass 

verge for nutrient control that will accommodate garbage bins for collection. 

5.6 DESIGN SPEED 

For the design of new roads reference shall be made to Development Control Plan No 

112 for the maximum design speed for various road classifications. 

The design speed for the redesign of existing roads shall generally be 10 km/h greater 

than the designated speed limit. This may be reduced to the designated speed limit 

when absolutely necessary on difficult sections of road. 

5.7 HORIZONTAL ALIGNMENT 

Where possible the radii of the curve should be maximised to reduce the necessity for 

centre line shift and widening of the carriageway. 

The need for road widening acquisitions shall be avoided wherever possible. 

The maximum horizontal deflection angle with out a horizontal curve shall be 1.5 degrees 

for urban roads and 1.0 degree for rural roads. 

5.8 CROSSFALLS AND SUPER-ELEVATION 

Desirably, roads shall be crowned in the centre and a standard 3% crossfall will apply to 

all urban roads. 

The use of super-elevation will only be permitted on major urban and rural roads with 

design speeds of 80kph or greater unless otherwise advised by the Project Manager. 

The use of super-elevating only part of the pavement, ie having an offset crown near the 

outer edge of the pavement, is to be discouraged for the following reasons: 

a 

a vehicle crossing the crown suddenly finds the super-elevation reversed with 

disconcerting effects; 

b paving machines applying an asphaltic concrete wearing course are often unable 

to match the crown because the break in the tamper is fixed and in any case has 

insufficient adjustment to give the necessary change of grade from 3% up to 3% 

down. 

In cases where super-elevation is impossible to avoid it should be limited to a desirable 

maximum value of 7% with an absolute maximum of 10%. 

23 



Superelevation and transitions shall be provided in accordance with either the current 

RTA Road Design Guide or the current Austroads Guide to Traffic Engineering Practice. 

5.9 TRANSITIONS AND WIDENING ON CURVES 

Plan transitioning and pavement widened shall be applied in accordance with the current 

RTA Design Guidelines. 

Where the travel lane width is 3.5m wide or greater the transition and widening of curves 

may be deleted for all urban roads except for main arterial roads. 

Roads with radii less than 40m shall be widened to allow for truck turning paths where 

necessary. 

5.10 LONGITUDINAL GRADING 

Desirable minimum 1% 

Absolute minimum 0.3% 

Desirable maximum 12.5% 

Absolute maximum 20% 

Where the longitudinal grade is less than 0.5% the normal crossfall should be increased 

to 4%. 

The above grades refer to gutters as well as centre line grades so exceptional care must 

be exercised in designing kerb returns, indented bus-bays and cul-de-sacs that the gutter 

grades do not vary above or below those specified. 

The maximum allowable grade in business and industrial areas shall be 12.5%. Kerb 

alignments are to be checked to ensure this grade is not exceeded around curves. 

At road intersections the longitudinal design shall allow for a vehicular holding platform 

with a maximum longitudinal gradient of 7% from the hold line for a distance of at least 

5.0 metres in urban areas and 15.0 metres in rural and industrial areas. 

It is important to consider the consequences of the location of sag low points when 

designing road grades. Sag low points shall preferably be located opposite side roads, 

drainage easements, public reserves or pathways to provide satisfactory secondary flow 

paths for occasions when the capacity of the drainage system is exceeded or when the 

system accidentally becomes blocked. 

Sign convention for indicating gradients shall be: 

+ ve for slopes ascending from left to right 

- ve for slopes descending from left to right 

24 



5.11 SIGHT DISTANCE 

Minimum stopping sight distances shall be provided based on the nominated design 

speed and shall be applied in accordance with the current RTA Design Guidelines. 

5.12 VERTICAL CURVES 

Vertical curves of the form of simple parabolas shall be provided at all changes in 

longitudinal grade. 

The vertical curve shall: 

a 

b 

c 

d 

not be shorter than 20.0 metres except at road junctions when the minimum shall 

be 10.0 metres measured from the line of the face of kerb of the through road; 

satisfy minimum sight distance requirements for the design speed; 

satisfy minimum riding comfort requirements. 

provide a reaction time of 1.5 seconds for urban areas and 2.5 seconds for rural 

areas for calculating stopping sight distance. 

The use of short sections of straight grade between vertical curves is undesirable for 

appearance and should be avoided. 

Where it is necessary to provide drainage at the lowest point of a sag curve, the distance 

(D) of the low point from the start of curve is given by: 

D = L ( R ) 

( R ) + ( r ) 

Where L = length of curve (horizontal projection) 

( R ) = absolute value of grade at start 

( r ) = absolute value of grade at end 

It may occur that the low point has to agree with an existing drainage system in which 

case the length of curve is fixed by the position of the low point. If the distance of the low 

point from the centre of the curve is "d" then the length of curve (L) is given by: 

L = 2d x ( R ) – ( r ) 

( R) + ( r ) 

Note: The correct sign convention must be used. 

Vertical curves on kerb returns must be treated in such a manner as to make 

construction practical. Kerb returns are formed as a series of chords and any vertical 

curves should be of sufficient length, with only minor changes of grade, to permit the use 

of formwork of reasonable length. 

25 



5.13 BATTERS 

Batters should be designed at stable slopes complying with the following slopes unless 

advised by a Geotechnical Engineer or requested by the project manger. 

Earth 

To facilitate maintenance of grassed batters in road reserves 

• Fill batter - desirable maximum 6 horizontal to 1 vertical (6:1). 

absolute maximum 4:1 

rural road design 2:1 batters may be considered where adequate 

bank stabilisation is provided. 

• Cut batter - desirable maximum 4:1 

Absolute maximum 1.5:1 may be considered where landscaped 

bank stabilisation is provided. 

Rock 

• Fill batter faced with large angular rock - maximum 1.5:1. A Structural Engineers 

design is required for rock batters greater than 1.5 meters in height 

• Cut batter - solid rock with few clay bands maximum 0.25:1. Less stable rock 

maximum batter 0.5:1. Where only short lengths of rock cuttings are encountered 

(30.0 metres or less) the rock cut batters should match any adjacent earth cut batters 

to improve aesthetics. 

For shallow batters (up to 1.0 metre in height) it is preferred practice to flatten batters as 

much as possible for the purpose of improved appearance. 

The need for constructing retaining walls should be avoided wherever possible. Should a 

retaining wall be necessary the Consultant must provide full engineering details of the 

proposed structure, including elevation and typical cross-section. 

Batters shall be designed to provide adequate stability for existing physical features and 

improvements on the footway where practicable to avoid the need for relocations or 

adjustments. 

Batters within new subdivisions or developments are to commence at the property 

boundary and intersect the natural surface prior to the proposed building alignment. An 

easement for support is to be provided where fill batters steeper than 4:1 encroach upon 

private land 

Lot access batters are to provide adequate sight distance in accordance with the design 

speed. This may require widening of footpath areas to achieve the required sight 

distance. 

26 



5.14 PROPERTY DRAINAGE 

Adequate provision shall be made for the collection of stormwater from properties or 

roofs that drain towards the road. 

Where the existing facility cannot be directed into either the proposed kerb and gutter or 

proposed longitudinal drainage system, then interallotment drainage shall be provided in 

accordance with Section 6.10 

The following pipe sizes are to be used in road reconstruction works when collecting 

property drainage and conveying flows to the kerb and gutter or street drainage system. 

Catchment area served (m²) Pipe Diameter (mm) Drainage connection 

Up to 600 100 Kerb and gutter 

600 to 1500 150 Street drainage system 



At locations where significant cost is likely to be involved in providing property drainage, 

consideration should be given to the economic viability of filling and restoring the 

property to eliminate the sag low point. 

27 



5.15 SUBSOIL DRAINS 

Where the top of kerb is at or below the level of the natural surface and where, in the 

opinion of the Project Manager it is considered necessary for the protection or drainage 

of the pavement, subsoil intercepting drains shall be provided. 

Subsoil drains and pits shall be shown on the plan view and will be located under the 

kerb and gutter except where any other location is specified by the Project Manager. 

Figure 4 of ARRB Special Report 41 should be used as a guide. 

5.16 KERB AND GUTTER 

All urban roads shall be provided with 150 mm integral kerb and gutter as detailed below 

. 

STANDARD KERB AND GUTTER 

. 

28 



5.17 KERB RAMPS 

Kerb ramps are to be placed at all intersection to facilitate pedestrian movements 

across roadways. The preferred location for kerb ramps is at the tangent point of the 

kerb return or a minimum of 7.0m back from the vehicular hold line. 

Existing kerb and gutter is to be removed the when installing kerb ramps. 

KERB RAMP DETAIL 

Kerb ramp to be 1:8 slope with 150mm rise from invert of gutter to top of ramp. 

Widen kerb ramp to 2500mm for cycleway ramps. 

Ramps to be 150mm thick concrete reinforced with F72 placed centrally. 

Provide expansion joints in kerb each side of the ramp. 

29 



All kerb ramps shall comply with AS1428:2 and provide a 45 degree cross brush 

angled haunching to the side of the ramp. Tactile ground surface indicators (TGSI's) shall be 

installed to the width of the kerb ramp to a depth of 300mm from the kerb lip. The TGSI's 

should be recessed into the kerb to ensure that they are flush with the surrounding pavement 

surface. The kerb lip shall ensure a smooth transition between the edge of the road and the 

kerb ramp. Refer to AS1428:4 2002 

30 



5.18 FOOTWAY CROSSINGS - VEHICULAR ACCESS 

Construction of vehicular access crossings shall generally be designed to cater for the 

RTA standard laden car with 130mm clearance. 

A preferred maximum longitudinal grade of 12.5% should be provided to all residential 

properties. Where site conditions necessitate, the longitudinal grade may be increased to 

an absolute maximum of 25% for private residents only. 

Maximum driveway profile grades for a private residence in a new subdivision to achieve 

garage floor levels at a standard 6.0m set back from the property boundary are provided 

in Appendix C 

Maximum driveway profile grades to comply with the RTA standard laden car with 

130mm clearance are provided in Appendix C. 

The plan view is to clearly show the full extent of access adjustments and is to indicate 

the length and height of retaining walls where required. 

The standard vehicular access crossing shall be as detailed below. 

Provide F72 reinforcement centrally placed in vehicular crossings serving standard 

residential carriageway or combined right of ways. 

5.19 INTERSECTIONS 

STANDARD VEHICULAR CROSSING 

Non-channelised intersections such as tee or crossroads shall be detailed by 

cross-sections at 10 metre interval and kerb return profiles on each leg. 

Desirable minimum kerb return radii are 8.0 metres for urban residential areas and 10.0 

metres for industrial areas measured from the face of kerb. 

Channelised or signalised intersections shall be detailed on each leg by cross-sections at 

10m intervals up to as close as practical to line intersection point. Within at least 40.0 

metres of the intersection point the traffic islands, kerb lines and medians shall be 

detailed by co-ordinates and design level at a maximum spacing of 5.0 metres in addition 

to the other geometric set out points such as tangent points and centre of circles. 

31 



At roundabouts the approach roads shall be defined by cross-sections at 10m intervals 

up to as close as practical to the intersection. Within 50.0 metres or any additional 

distance necessary to accurately set out any curves in the various kerb lines the 

intersection geometry shall be defined by co-ordinates and design level at a maximum 

spacing of 5.0 metres in addition to other geometric set out points such as:- 

• at all tangent points 

• for all centres of curves 

• at all drainage pits 

• at all kerb angle points 

Co-ordinates shall be provided to permit the setting out of line markings. 

The co-ordinates provided shall relate to an appropriate control line positions and clearly 

defined on the design plan. Co-ordinates values are to be expressed to three (3) decimal 

places with reduced levels rounded off to the nearest five (5) millimetres. 

All intersections including roundabouts and associated pavement areas shall be 

contoured at 0.1 metre intervals to confirm the road crossfall and drainage pattern for the 

intersection. 

Both concept and final design plans shall include a design surface contour. 

5.20 CUL-DE-SAC AND HAMMER HEAD FACILITIES 

The following minimum requirements will apply to turning facilities 

A 

Cul-de-sacs 

i 

ii 

Residential areas a minimum 8.5 m radius to the face of gutter shall be 

provided. 

Industrial areas a minimum 13.50m radius to the face of gutter shall be 

provided. 

B 

Hammer Heads 

Variations of hammerhead turning facilities will be permitted where site conditions 

do not allow the provision of a cul-de-sac. 

C 

The following grades and cross falls shall apply to all turning facilities: 

Desirable minimum 1.0% 

Absolute minimum 0.5% 

Desirable maximum 5% 

Absolute maximum 7% 

D 

Parking facilities where required, are to be provided outside the minimum turning 

area. 

32 



5.21 TRAFFIC CONTROL DEVICES 

Traffic control devices are to be provided to reduce travel speeds in accordance with the 

nominated design speed generally where road geometry cannot satisfy this requirement. 

They are also used in conjunction with landscaping to identify road classes within the 

road hierarchy and to enhance the urban streetscape. 

Such devices are to be designed and spaced in accordance with current engineering 

practices and are to be approved by the Project Manager. 

5.22 FOOTPATHS 

A minimum 1.2m wide reinforced concrete footpaths shall be provided on at least one 

side of the roadway and on both sides of main roads. Shared footpath / cycleway shall 

be a minimum 2.5m wide 

Footpaths shall generally be located 600mm off the boundary and be constructed from 

100mm thick, F72 reinforced concrete. 

In steep areas where the depth of cutting or embankment is consistently greater than 2.0 

metres Council may give consideration to a reduction in the width of footway formation in 

urban areas to a minimum of 2.0 metres to allow for the provision of a footpath and grass 

verge for nutrient control that will accommodate garbage bins for collection. In these 

areas the footpath is to be located 800mm off the face of kerb. 

The footpath shall be constructed with a crossfall of 2% (maximum 2.5%). 

The longitudinal grade is to generally match the adjacent roadway with an absolute 

minimum grade of 0.5% and a desirable maximum grade of 12.5%. 

Where grades exceed 12.5% consideration shall be given to provision of steps to reduce 

the longitudinal grade to an acceptable grade. 

5.23 CYCLEWAYS 

Both shared paths and on road cycleways are to conform with the current Austroads 

Guide to Traffic Engineering Practice Part 14 (Bicycles) and the NSW RTA Bicycle 

Guidelines. 

SHARED PATHS 

Off road shared paths should be marked with a centerline to separate two way flows 

and to permit safe operation of the facility. Shared paths are part of the road related 

area and are usually separated by a dividing strip to a buffering distance of 500mm. 

They are regulated by the sign R8-2A. PS-3, PS-4 and PA-1 pavement arrows are 

used in an advisory capacity at 70m intervals or adjacent to intersecting paths/ 

intersections. 

33 



ON ROAD CYCLEWAYS 

On road cycle lanes should be considered on all roads, in particular those identified 

on the 2002 Adopted GCC Bicycle Network. Cycle lanes are to be generally 1.5m 

wide with a minimum of 1.2m or in special circumstances (such as to the left of traffic 

calming devices), an absolute minimum of 1m. 

5.24 EROSION AND SEDIMENTATION CONTROL 

The soils of the Gosford region are generally fragile and susceptible to erosion. The 

disturbance of vegetation and soil surfaces should be kept to a minimum and the 

implementation of suitable erosion and sedimentation control measures applied in 

accordance with Council’s Code of Practice – Erosion and Sedimentation Control. 

A separate Erosion and Sedimentation Control Plan is to be provided with each project. 

5.25 PROPERTY ADJUSTMENT 

Generally the adjustment of levels within individual properties is to be avoided. The 

Consultant is required to match existing boundary levels or design suitable retaining 

walls to contain road works within the road reserve. 

Where driveway access adjustments are necessary a longitudinal section profile along 

each driveway is to be provided indicating the proposed new grades. Where driveways 

are skew to the carriageway then a longitudinal section along the critical shortest edge of 

the driveway is to be provided. 

5.26 PHOTOGRAPHIC RECORDS 

When requested by Council, colour photographs are to be taken of properties requiring 

adjustment. A copy of the photographs are to be included in the design report to record 

the extent and condition of existing landscaping, the existing boundary fence, the existing 

driveway and relevant details that could avoid a dispute after adjustments have been 

carried out. 

5.27 LANDSCAPING 

Wherever practical large medians, verges and islands should be landscaped in 

preference to grass or continuous hard surface treatments. 

The choice of planting should preferably be made on species occurring naturally in the 

area with local variations in soil type and moisture content taken into account. 

Opportunities for 'gateways' or cultural planting should also be identified. 

Landscaping should be located so as not to impair visibility for motorists and pedestrians. 

Species used in landscaping drawings must not conflict with overhead power lines or 

Telecommunication cables and must not present a safety hazard (ie located within the 

clear zone) to vehicles when fully grown. 

34 



Council’s clear zones are to be kept clear of all but low growing species. These species 

should not exceed 1.0 metre in height. Clear zone widths are 2.5 metres absolute 

minimum, 3.0 metres preferred from the edge of the running lane or kerb face for speeds 

up to 60 kph, ranging up to 9.0 metres for 100 kph. 

Special consideration should be given to Traffic Signal sites to ensure that mature trees 

do not obscure visibility to the signs and lanterns. Similarly at roundabout sites, the 

visibility of entering and circulating vehicles should not be obscured by mature plants. 

In medians and islands a minimum clear width of between 0.5 metres and 1.0 m 

(depending on the relative width of the median) is required behind the kerb face and this 

area should be treated with paving. 

Sub-soil drainage and watering facilities are to be provided to all landscaped areas. 

Consideration should be given to the installation of suitable root barrier systems for tree 

planted adjacent to road pavement areas 

5.28 PUBLIC UTILITIES 

Major public utility adjustments often prevent the proposed works from proceeding 

because of the costs of relocation. The Consultant therefore must accurately locate 

surface and underground utility in critical locations in respect of type, size, horizontal and 

vertical placement. This can mean removal of pit lids for inspection, electronic detection 

and trench excavation for physical exposure of the utilities where site conditions dictate. 

Where a utility is unable to be located and or an assumed depth is adopted than a clear 

highlighted note is to be provided on the plan view and associated longitudinal section 

indicating assumed location and depth unknown 

5.29 ROADLOC REFERENCES 

All classified Main Road projects are to have a Roadloc reference shown in the title 

blocks. Council will provide the Roadloc references. 

The traffic signal design shall include an ISG co-ordinates at the centre of the 

intersection to meet RTA requirements 

5.30 SURVEY MARKS 

All survey marks must be preserved if possible. If disturbance is unavoidable then a note 

is to be provided on the design plan for the re-establishment of the survey mark. 

Permanent Marks and State Survey Marks should be clearly shown on the drawings and 

setting out sheets. These marks are to be identified by the boxed annotation - This Mark 

Must Be Preserved. If the reference mark is located off the sheet, suitable annotation 

should be shown on the nearest extremity of the setting out sheet. 

35 



5.31 DESIGN REPORT 

Each Project is to be accompanied by a design report, which provides summarised 

information and data detailing relevant background information. 

The design report is to provide backup data which could be referred to in the future if and 

when further upgrading is contemplated or problems become evident. This particularly 

relates to drainage design where it is not unusual for problems to become evident some 

years after construction. 

Depending on the requirements specified in the Project of this Brief, the design report 

may include 

‣ Output of traffic modelling from INTANAL 

‣ Drainage catchment drawings and output from drainage software 

‣ Geotechnical test data and pavement design calculations and considerations 

‣ Summarised structural calculations or computer output 

‣ Relevant photographs, particularly of properties requiring adjustment 

‣ Review of Environmental Factors 

‣ Schedule of Quantities 

‣ Estimate of Cost 

‣ Apportionment of Cost to Council and RTA 

‣ Copies of correspondence with utility authorities, other agencies, and interested 

outside parties, and 

‣ Minutes of meeting with Council Officers and interested outside parties. 

5.32 PAVEMENT DESIGN 

Pavement thickness design shall be in accordance with the following publications: 

• AUSTROADS (1992) Pavement Design, A guide to the Structural Design of Road 

Pavements, Sydney - for ESA > 10 6 

• ARRB Special Report _ 41 (1989) Into a New Age of Pavement Design, A Structural 

Design Guide for Flexible Residential Street Pavements - for ESA < 10 6 , Residential 

Only 

Subgrade conditions including CBR's and depths to rock are to be confirmed by a 

practising geotechnical engineer. Three (3) copies of the completed geotechnical report 

shall be submitted with the preliminary pavement design. 

The proposed pavement construction and materials shall be confirmed with the Project 

Manager early in the design process. 

The traffic loading to be used will be provided by the Project Manager at the 

commencement of the project design. 

36 



37 




38 



SECTION 6 

STORMWATER DRAINAGE DESIGN 

6.1 GENERAL 

Stormwater drainage systems shall be designed to satisfy the following objectives: 

1 The inundation of private and public land and buildings is minimised and that 

surface flow routes convey floodwaters below the prescribed velocity/depth limits. 

2 The convenience and safety for pedestrians and traffic affected by frequent 

stormwater flows is maximised by controlling those flows within prescribed limits. 

3 The retention within each catchment as much incident rainfall and runoff as is 

appropriate for the planned use and characteristics of the catchment. 

4 That the proposed system is designed with consideration of all ultimate and interim 

upstream and downstream characteristics and that the proposal operates as a 

total system and does not adversely affect any systems or property within the 

catchment. 

5 That stormwater is adequately treated to remove pollutants and systems provided 

to replenish subsurface flows in appropriate locations. 

6 Erosion and sedimentation is minimised to acceptable levels. 

7 To minimise maintenance requirements and enhance the urban landscape where 

possible. 

8 Open channel design to satisfy N.S.W Fisheries, Department of Infrastructure 

Planning & Natural Resources (DIPNR) and Rivercare guidelines. 

39 




In pursuit of the above objectives, the following principles shall apply: 

1 Councils designated drainage design return interval standard is the 1% A.E.P. 

flood event. 

2 New Developments are to provide a stormwater drainage system in accordance 

with the “major/minor” system concept set out in Book Eight Urban Stormwater 

Management of Australian Rainfall & Runoff, 2000 (AR&R 2000). 

A major system comprises planned and unplanned drainage routes, which convey 

runoff from major storms to trunk drains and shall provide safe, well-defined 

overland flow paths 

A minor system is the collection structures, gutter and pipe network capable of 

collecting and carrying runoff from minor storms. 

Design Average Recurrence Interval (ARI) – For “major/minor” systems are given 

in Table 6.1 

3 Redevelopment – Where the proposed development replaces an existing 

development, the on-site drainage system is to be designed so that the design 

average recurrence interval estimated peak flow from the development site to the 

receiving minor system, is no greater than that which would be expected from the 

existing development. The downstream system is to be reviewed to ensure the 

system is not adversely affected. Such stormwater drainage systems are to be 

designed in accordance with AR&R 2000. 

4 The requirements of Council’s Flood Management Policy and Set back Policy – 

Creeks, Rivers & Lagoons and Councils procedures for developments adjacent 

easements shall be adhered to for all developments. 

5 The NSW Government Floodplain Management Manual (January 2001) velocity 

and depth relationship refer Appendix L. 

6 The requirements of N.S.W Fisheries, DIPNR and Rivercare guidelines 

6.3 HYDROLOGY 

6.3.1 Design Rainfall Data 

1 Design Intensity-Frequency-Duration (IFD) Rainfall – IFD relationships 

shall be derived in accordance with Book Two Design Rainfall 

Considerations AR&R 2000 for the particular catchment 

2 For convenience design IFD rainfall tables are provided for general zones 

within Gosford. Refer Appendix E. 

3 Design recurrence intervals for various drainage situations are provided in 

Table 6.1 

40 



Table 6.1 

Major/Minor System Design ARI 

Drainage Situation Minor System Major System 

1 Residential streets and 

catch drains with overflow or 

bypass along the street 

2 Residential streets and 

catch drains at low points 

with overflow along public 

reserves and pathways 

3 Existing residential streets 

and catch drains at low 

points with drainage lines 

traversing building 

allotments or other locations 

where surface flow may 

cause property damage 

10 Years 

10 years 

20 years 

generally, 100 

years if no 

escape route 

100 year flood to be confined to 

carriageway. 

Consider depth / velocity ratio for safe 

vehicular and pedestrian access 

100 year flood to be confined to 

carriageway, pathway or reserve 

Consider depth / velocity ratio for safe 

vehicular and pedestrian access 

A 50% blockage factor is to be adopted 

for the under ground drainage system. 

The extent of the 100 year flood is to be 

shown on the plans so that appropriate 

easement width and treatment of 

escape route can be determined 

Headwall trash racks are to be provided 

to avoid blockage from debris. 

4 Trunk system traversing 

developed areas 

(residential, commercial or 

industrial) 

(Trunk systems are those 

having catchment areas in 

excess of 15 ha or having 

100 year ARI runoffs in 

excess of 3 m³/second 

whichever is the lesser.) 

100 years A 50% blockage factor is to be adopted 








5 Industrial and business 

areas 

20 years 

generally, 100 

years if no 

escape route 

A 50% blockage factor is to be adopted 








41 



Overland system flow paths within developments such as pathways or 

roadways shall cater for the 100 year ARI event minus 50% of the minor 

piped flow , eg 10 year ARI, see above. 

4 Where a development is designed with an overland flows path across 

private property, then the underground system, both culverts and inlets 

shall be designed to capture and contain flows having an ARI of 100 

years from the upstream catchment. An emergency overland flow path 

shall also be provided for these systems that will cater of 50% of the 100 

year flow. Easements are to be provided in private property over such 

pipe systems and overland flow paths. Restrictions shall also be placed 

on the property so as not to permit changes in surface levels or the 

construction of certain structures within these easements. 

6.3.2 Catchment Area 

1 The catchment area is defined by the limits from where surface run off will 

make its way, either by natural or man made paths, to a collection point. 

Consideration shall be given to likely changes to individual catchment 

areas due to the full development of the catchment. 

2 Where no detailed survey of the catchment is available, 1:4000 

topographical maps with 2m contour intervals may be used to determine 

the catchment and to measure areas. These maps are available from the 

Department of Lands, Land and Property Information Service and can be 

viewed at www.lands.nsw.gov.au 

3 Catchment area land use shall be based on current available zoning 

information or proposed future zonings, where applicable ie, the ultimate 

developed state of each catchment including all contributing catchments. 

4 A contoured catchment area plan with cadastral boundary and subcatchments 

are to be provided as part of the detail design. 

5 The sizing of catchment areas for street drainage shall not take into 

consideration interallotment drainage. This is to ensure adequate 

collection pits are provided within street system. 

42 



6.3.3 Hydrological Models 

6.3.3.1 Rational Method 

1 Rational Method calculations to determine peak flows shall be carried out 

in accordance with AR&R and the requirements of this Specification. 

2 A qualified person experienced in hydrologic and hydraulic design shall 

carry out all calculations. The results are to be submitted for approval in a 

format similar to that shown in appendix B. An explanation of the 

calculation form columns and their use is provided in appendix M. 

3 Co-efficient of Run-off for urban areas shall be derived from the following 

equation 

Cy = Fy x C10 

Where 

- Cy is the Coefficient of run-off for the design recurrence 

interval 

- Fy is Frequency factor from table 6.2 

- C10 is the coefficient of run-off for the 10 year recurrence 

interval obtained from Appendix E Figure E2 Urban Runoff 

Coefficient 

- Full details of the run-off co-efficients utilised shall be 

provided 

Table 6.2 

Average Recurrence Interval (years) 

Catchment Type 1 2 5 10 20 50 100 

Urban (Fy) 0.80 0.85 0.95 1.00 1.05 1.15 1.20 

Rural/Natural 

(FFy) 0.62 0.74 0.88 1.00 1.12 1.26 1.39 

4 The absolute minimum impervious percentage for single residential lots 

shall be 70%. 

5 The percentage impervious for various zoning areas are provided in 

Appendix K and shall be adopted unless calculations are provided to 

substantiate the adoption of a different value. 

6 The time of concentration of a catchment (tc) is defined as the time 

required for storm runoff to flow from the most remote point on the 

catchment to the outlet of the catchment. tc shall be for the ultimate 

43 



developed catchment generally catering for the greatest flow. 

Consideration shall be given that natural or developed catchments have 

defined flow paths and sheet flows generally occur for short distances 

only. The tc should be calculated using a combination of the Kinematic 

Wave and Manning’s formula to determine as accurately as possible the 

actual tc. Unless sufficient evidence is provided, the Kinematic Wave 

equation shall be used for a maximum 50 metre length in determining the 

tc. 

7 Where the flow path is through areas having different flow characteristics 

or includes property and roadway, then the flow time of each portion of 

the flow path shall be calculated separately. 

8 The maximum tc in an urban area shall be 20 minutes unless sufficient 

evidence is provided to justify a greater time. The tc in rural areas shall 

be calculated in accordance with Section 5.4 of AR&R 2000. 

9 Flow paths to pits shall be representative of the fully developed catchment 

considering such things as fencing and the likely locations of buildings 

and shall be shown for each collection pit on the catchment area plan. 

Consideration shall be given to likely changes to individual flow paths due 

to the full development of the catchment. Refer point 5 above. 

10 Surface roughness co-efficient “n” shall be adopted from information 

provided in AR&R and should be verified by the Engineer. Values 

applicable to specific zoning types and overland flow path types are given 

below: 

Surface/Zoning 

Roughness Co-efficient 

“n” 

Flow across Parks 0.35 

Flow across Rural Residential land 0.30 

Flow across Residential (2a) 0.21 

Flow across Residential (2b) 0.11 

Flow across Industrial 0.06 

Flow across Commercial 0.04 

Flow across Asphalt Roads 0.012 

Flow across Paved Areas 0.01 

Flow across Gravel Areas 0.02 

Flow lengths are to be kept to a minimum prior to assuming entry into a 

gutter or piped system. 

44 



6.3.3.2 Other Hydrological Models 

1 Other hydrological models may be used as long as the requirements of 

AR&R 2000 are met, summaries of calculations shall be provided as well 

as details of all program input and output. 

2 Where computer analysis programs are used, copies of the final data files 

of the design shall be provided to the Accredited Certifier with the final 

drawings for approval by the Accredited Certifier. Details on the use of 

specific programs, catchment parameters and any other relevant 

information shall also be submitted. 

45 



6.4 HYDRAULICS 

6.4.1 Hydraulic Grade Line 

1 Hydraulic calculations shall generally be carried out in accordance with 

AR&R and shall be undertaken by a qualified person experienced in 

hydrologic and hydraulic design. The calculations shall substantiate the 

hydraulic grade line adopted for design of the system and shown on the 

drawings. Summaries of calculations shall be shown on the plan and 

details of all calculations shall be submitted including listings of all 

programme input and output. 

2 The “major” system shall provide safe, well-defined overland flow paths 

for the 100 year ARI storm runoff events while the “minor” system shall be 

capable of carrying and controlling flows from frequent runoff events. 

3 Downstream hydraulic grade line level requirements for design are as 

follows: 

i 

ii 

iii 

Known hydraulic grade line level from downstream calculations 

including pit losses at the starting pit in the design event. 

Where the downstream starting point is a pit and the hydraulic grade 

line is unknown, levels of 0.15m below the pit inlet in the 

downstream pit is to be adopted. 

Where the outlet is an open channel and the design storm is the 

minor event the top of the outlet pipe shall be the downstream 

control. 

iv Where the outlet is an open channel, the design storm is the 100 

year ARI event and downstream flood levels are not known, the top 

of the outlet pipe shall be the downstream control unless otherwise 

nominated by the Engineer where the consultant shall estimate the 

downstream level taking into account backwater affect. 

v Where the outlet is an open channel, the design storm is the 100 

year ARI event and downstream flood levels are known, the 

downstream control shall be the 100 year ARI design flood level as 

per Appendix J. Where future 100 year ARI flood levels are lower 

than the existing, the higher flood level shall be adopted. 

vi 

Where the outlet is at a river or lake the design 100 year ARI flood 

level shall be the downstream control as per Appendix J 

4 The hydraulic grade line level in drainage pits shall be limited to 0.15m 

below the gutter invert and 0.15m below the inlet surface level for junction 

pits. 

46 



6.4.2 Gutter flow 

1 The maximum permissible flow along a kerb and guttered road shall be 

determined from Appendix F fig 1 

2 If the calculated gutter flow is greater than the maximum permissible 

gutter flow obtained from Appendix F figure 1 then the pit location shall be 

changed or additional pits provided to reduce the inlet flow. 

3 Where a vehicular travelling lane is adjacent the kerb then the maximum 

tolerable depth of flow is considered to be 75mm. 

4 For kerb side parking lanes or cycleway adjacent to the kerb the 

maximum tolerable depth of gutter flow is to be 125mm. 

5 Where a roadway is intended to act as a secondary flow path then to 

ensure public safety within the overland flow paths, the depth of flow 

should generally be less than 0.2 metres and the velocity is less than 

1m/sec ( Refer Appendix L } 

6.4.3 Culverts 

1. Minimum conduit sizes for areas to be in Council control are: 

• The minimum pipe size shall be 375mm diameter. 

• The minimum box culvert size shall be 600mm wide x 300mm high. 

2. Minimum and maximum velocity of flows in stormwater pipelines shall be 

0.6m/sec and 8m/sec respectively. 

3. Reinforced concrete culverts are to be specified for all drainage works that 

will be under the control and maintained by Gosford City Council. 

6.4.4 Pits 

1 Inlet pits shall be located to prevent ponding and to limit flow widths and 

depths to acceptable levels in accordance with this specification. 

Preference shall be given to the location of drainage pits at the upstream 

side of lots, pedestrian crossing points and kerb returns. 

2 Pits shall also be provided: 

• To enable access for maintenance 

• At changes in pipeline direction, grade, size, level or class of pipe 

• At junctions of pipelines 

• Where an existing downstream development could be adversely 

effected by major system flows from a new development as a result 

47 



of the 50% blockage factor in Table 6.1. Additional collection 

structures shall be provided to ensure the minor system is fully 

loaded before it reaches the existing developed area. 

3 Pits are to conform to Council’s current Standard Drawings and 

nominated RTA Standards where no Council standard exists. 

4 Step irons shall be provided in all pits deeper than 1.2m, unless otherwise 

warranted. 

5 The maximum recommended spacing of pits where flow widths are not 

critical is 80m 

6 Kerb inlet lengths (lintels) are to be 

• minimum 1.8 m 

• maximum 3.0 m 

• Absolute maximum ( Council approval required) 3.6 m 

Kerb inlet lengths refer to clear opening. There shall be a minimum 

150mm step down to the race from the gutter invert level at the lintel. 

7 All grates within road reserves and pathways shall be bicycle friendly and 

secured in an approved fashion to permit access only to maintenance 

personnel. 

8 All grate loading requirements shall conform to the intended use of the 

grate or adjacent area. 

9 Pits should collect as much stormwater as possible while maintaining safe 

designs for pedestrian, vehicular and cycle traffic. Letterbox inlets pit are 

to have a maximum opening of 150mm with the pit lid over lapping the pit 

wall to prevent a vertical drop into the pit. 

10 All pipelines, including roof and subsoil pipes, shall enter the main pipe 

system at a pit. These shall be finished off flush and be grouted into the 

pit wall to the satisfaction of Council. 

6.4.5 Hydraulic Losses 

1. The 'K' value is the Pressure Head Change Coefficient for a headwall, pit or 

pipe bend. It shall normally be derived from the appropriate figures given in 

Appendix H. However, if an unusual pit configuration arises then an 

acceptable 'K' value shall be determined following discussions with the Project 

Manager. 

2. Figures H1 to H11 are only DIRECTLY applicable to pipelines constructed "in 

line". That is, with both the inlet and outlet pipelines at a pit aligned vertically 

between matching inverts and matching obverts and with similar lateral 

alignment. The pipe centerline must also intersect at or near the downstream 

face of the pit. 

48 



When pipelines at a pit are not "in line" (ie "offset"), the value of 'K' obtained 

from Figure H12 shall be added to the value obtained from Figures H6 to H11. 

3. At the junction of two pipelines where a significant offset through the pit occurs 

(i.e. h/Du Ratio 1.6 - see Figure H12) then a value of K = 3.0 shall be used, 

i.e. similar to grate inflow only. 

4. At the junction of three pipelines the following guidelines for the use of 

Figure H12 shall be adopted. 

• Where only one inlet pipeline is offset from the outlet pipeline then:- 

a if the upstream pipeline (DU) is offset, use h/DU for the pipeline offset 

ratio in Figure H12, or 

b if the lateral pipeline (DL) is offset, use h/DL for the pipeline offset ratio 

in Figure H12. 

• Where both inlet pipelines are offset from the outlet pipeline then:- 

a if (QU x hU) ≥ (QL x hL) - use hU/DU for the pipeline offset ratio with QU 

= QDROP in Figure H12, or 

b if (QU x hU) < (QL x hL) - use hL/DL for the pipeline offset ratio with QL = 

QDROP in Figure H12. 

5. If the total value of 'K' determined from Figures H5 and H6 plus the value of 'K' 

obtained in accordance with Clause 6.4.5.4 above is greater than 3.0, then 

a value of K = 3.0 should be adopted for the pit. 

6. Computer program default pressure change co-efficient “K” shall not be 

acceptable unless they are consistent with “1” above. 

7. Going from larger upstream to smaller downstream conduits is not permitted 

8. Drainage pipe systems shall be designed as an overall system, with due 

regard to the upstream and downstream system and not as individual pipe 

lengths. Drainage pipeline systems shall generally be designed as gravity 

systems flowing full at design discharge, but may be pressurised. Pipe 

friction losses and pipe sizes in relation to discharge shall be determined 

using the Colebrook-White formula with the following roughness co-efficient 

being 0.6mm for concrete pipes, 0.06mm for FRC pipes and UPVC pipes. 

49 



6.5 OVERLAND FLOW PATHS 

6.5.1 General 

Overland flow paths shall be provided to convey flows that exceed the capacity of 

the minor drainage system to trunk drainage systems that cater for the design 

100 year ARI flows. 

Such flow paths are generally roadways and pathways linked together that 

contain and convey these flows at acceptable depths and velocities. 

Occasionally it may be necessary to either widen flow paths or increase the size 

of the minor system to cater for such flows. 

To ensure public safety within overland flow paths, the depth of flow should 

generally be less than 0.2 metres and the velocity is less than 1m/sec (Refer 

Appendix L). 

Calculations sufficient to substantiate the design satisfying the above 

requirements with the required freeboard are to be submitted for approval. 

It should be noted that it is critical to adequately design the inlet to such overland 

flow pathways to ensure the design flows are conveyed into the flow paths and 

the flows do not bypass the system and inundate property. 

6.5.2 Freeboard 

1. A minimum 100mm freeboard will be required between the calculated 100 

year ARI flow level in the gutter area and the high point in the footpath to all 

properties, specifically properties at a lower level than the adjacent road 

formation. 

Driveway construction in these instances must ensure this requirement is 

satisfied. 

2. Overland flow paths, (eg at the end of cul-de-sacs that drain trapped low 

points) shall have a minimum 300mm freeboard from the calculated 100 year 

ARI flow level to any adjacent residential allotment and a minimum of 500mm 

freeboard to habitable floor levels. 

Where overland flow pathways are located generally parallel to the contour of 

the land, a minimum 100mm freeboard from the design 100 year ARI flow 

level to the boundary level shall be provided. The adjacent low side dwelling 

shall have floor levels a minimum of 500mm above the surrounding area 

draining towards the street eg, no trapped low points. 

50 



51 



6.6 OPEN CHANNELS 

1 Generally, open channels form part of the trunk drainage system that cater for 

major event (100 year ARI or greater) flows and shall be designed to have smooth 

transitions with adequate access provisions for maintenance and cleaning. 

2 The Open channel design is to satisfy N.S.W Fisheries and the DIPNR Rivercare 

guidelines for Ecological Sustainable Management of Rivers and Riparian 

Vegetation. As standards are constantly changing it is recommended that prior to 

undertaking an open channel both N.S.W Fisheries and the DIPNR be contacted 

regarding current design guidelines. 

3 Design of open channels shall be generally in accordance with AR&R 2000. 

4 Friction losses adopted for open channel design shall be determined using 

Manning’s “n” values (see below). Due to the length of time between maintenance 

periods, open channels are to be designed for the worst case. Ie an over grown 

channel section with full vegetation regrowth with a Mannings “n” = 0.085. 

Manning’s “n” Roughness Co-efficient for open channels shall generally be derived 

from information AR&R 2000. Mannings “n” values applicable to specific channel 

types are given below:- 

Concrete Pipes or Box Sections 0.011 

Concrete (trowel finish) 0.014 

Concrete (formed without finishing) 0.016 

Sprayed Concrete (gunite) 0.018 

Bitumen Seal 0.018 

Bricks or pavers 0.015 

Pitchers or dressed stone on mortar 0.016 

Rubble Masonry or Random stone in mortar 0.028 

Rock Lining or Rip-Rap 0.028 

Corrugated Metal 0.027 

Earth (clear) 0.022 

Earth (with weeds and gravel) 0.028 

Rock Cut 0.038 

Short Grass 0.033 

Long Grass 0.043 

Natural Channel Designs 0.085 

5 Where constraints do not permit the provision of open channel design specified 

herein or adequate safety treatments, man proof fencing of the channel section 

shall be provided with due regard for maintenance and emergency access. 

6 Maximum side slopes on conventional grass lined open channels shall be 1 in 6. 

7 Open channels shall be designed to provide meandering low flow inverts within the 

main channel. 

52 



8 Sub-surface drainage may be required in grass lined channels to prevent 

waterlogging of the channel bed. 

9 The low flow system shall be designed to convey an ARI 2 year flows. The low 

flow capacity will depend on the invert type, catchment characteristics, low flow 

velocities etc, however the minimum size of the low flow treatment shall be a 1.0m 

wide by 100mm deep section. 

10 The low flow system is to be designed to pond water to a minimum depth of 

100mm along its full length or provide rock drop structures with a maximum drop of 

200mm. The drop structure is to be designed to current DIPNR and Rivercare 

requirements. 

11 Where drops exceed 200mm a fish ladder to NSW Fisheries details are to be 

provided at a maximum 1:20 slope. A review of the design shall be undertaken by 

NSW Fisheries to confirm current design standards. 

12 Low flow pipes will not be permitted. 

13 Sour protection shall be provided along the toe of banks to a minimum height of 

1.0m where high velocities are expected in the low flow channel. 

14 The following should be avoided or designs carried out to adequately 

accommodate the following: 

• Hydraulic jumps/supercritical flows 

• Transitions and constructions of the channel – backwater effect 

• Superelevated flows (around bends) 

• Freeboard/provisions for debris under structures, mine subsidence, etc 

15 A minimum 300mm freeboard shall be provided to the top of the channel. 

16 Adjacent dwellings should have habitable floor levels a minimum of 500mm above 

the estimated 100 year flood level. 

17 Provision shall be made for a minimum 4.0m wide access track along any open 

channel in accordance with Council’s set back policy. 

6.7 MAJOR STRUCTURES 

1 Major structures refers to large man made structure that may restrict the flow of a 

water body and includes bridges and large box culverts. 

2 All major structures shall be designed for the 100 year ARI event and in 

accordance with Councils flood policy. The policy requires that new structures do 

not increase the 100 year flood level more than 10mm for areas out side the 

development site both upstream and down stream of the structure or out side the 

immediate site. 

3 Major structures within rural areas shall be designed to accommodate the100 year 

53 



ARI flood events. A maximum 200mm depth of flow combined with a maximum 

velocity of 1m/s is permitted over the top of the structure (Refer Appendix L). 

4 A minimum clearance of 500mm between the 100 year ARI flood level and the 

underside of any bridge superstructure is required to allow for passage of debris 

without blockage. 

5 Certified structural design shall be required on bridges and other major culvert 

structures and may be required on some specialised structures. The design shall 

be carried out in accordance with AUSTROADS (1992) Bridge Design Code. 

6 Culverts (either pipe or box section) shall be designed with due regard being given 

to inlet and exit losses, inlet and outlet control and scour protection. 

6.8 RETARDING BASINS 

1 Stormwater detention facilities are to be designed to control run off from all storm 

events from a 1 year event up to the Probable Maximum Flood (PMF), for any 

duration. The ultimate developed catchment area under current land zoning’s shall 

be used to determine peak flows. The design peak discharge at all locations 

downstream shall not exceed the existing peak flow prior to the development for 

the 100 year ARI flood event. 

2 Storm patterns shall be those given in AR&R 1987 Volume II. 

3 The design is to evaluate the following storm events 1, 5,10, 20, 50,100 year and 

the PMF. The results shall be presented in a tabular form for clear comparison 

between existing and proposed conditions. 

4 The high level outlet to any retarding basin should have a capacity to contain the 

design flow between the 100 year ARI flood event and the PMF. 

5 Additional spillway capacity may be required due to the hazard category of the 

structure. The hazard category should be determined by reference to ANCOLD 

(Australian National Conference on Large Dams 1986). 

6 The spillway design shall generally be in accordance with the requirements for 

Open Channel Design in this Specification and should be approximately 500mm 

lower than the rest of the embankment. Adequate reinforcing and scour protection 

shall be provided to the spillway to minimise the possibility of embankment failure 

during overtopping. 

7 Pipe systems shall contain the design flow through the Retarding Basin wall and 

be suitably protected to prevent infiltration of water between the pipe outer surface 

and the basin wall. 

8 The basin outlet structure shall be designed to prevent blockages. 

9 The pipe outlet shall be designed to reduce outlet velocities and prevent 

downstream erosion. 

54 



10 Freeboard – Minimum floor levels of dwelling shall be a minimum of 500mm above 

the design water level at the emergency spillway when in operation. Refer point 4 

above. 

11 Public Safety Issues – Basin design is to consider the following aspects relating to 

public safety. 

• Side slopes are to be a maximum of 1 in 6 to allow easy egress. 

• Water depths shall be, where possible, less than 1.2m in the 20 year ARI 

storm event. Where either requirement is not practical or economic, 

greater depths may be acceptable. In that case the provision of safety 

refuge mounds should be considered. 

• Depth indicators should be provided indicating maximum depth in the 

basin. 

• The desirable minimum slope of the basin floor is to be 1%. Slightly 

higher grades 1% to 2% should be adopted where sporting fields are 

located within basins. 

• Protection of the pipe outlet structure shall be undertaken to reduce 

hazards for people trapped in the basin. 

• Signage of the spillway and basin is necessary to indicate the hazard. 

• No planting of trees or large shrubs on basin walls is permitted. 

• No basin spillway is to be located directly upstream of dwellings and shall 

be controlled to prevent run off entering private property. 

• Submission of the design plans to the Dam Safety Committee for 

approval. 

PO Box 3720 

Parramatta NSW 2124 

Phone: 02 9895 7363 

Fax: 02 9895 7354 

E-mail: dsc@damsafety.nsw.gov.au 

6.9 ON-SITE STORMWATER DETENTION 

1 On-site stormwater detention will be required where considered necessary by the 

Engineer on redevelopment sites to attenuate the run off to discharge levels 

expected from the pre-developed site, for the minor and major events. 

2 All designs shall be in accordance with Council’s Draft On-site Stormwater 

Detention Draft Policy 

3 Calculations are to include any upstream catchments, which contribute to the run 

off. 

55 



4 Various storm duration’s are to be modelled to determine the critical duration both 

pre and post development. 

5 The temporary storage of water is to be contained within the site, and is not to 

encroach on adjacent properties or public and road reserves. Pedestrian access 

is not to be included within the storage area unless readily available alternative 

routes are provided. 

6 Enclosed structures are not favoured due to maintenance problems and the unit 

being out of sight of visual inspection. 

7 The maximum water depth for the 100 year ARI event is 200mm for car parks, and 

600mm for gardens. 

8 An overland flow path (or spillway) must be provided for the on-site detention area. 

A minimum freeboard of 500mm must be provided to floor levels (including 

adjacent properties) for the 100 year ARI event, assuming 100% blockage of the 

piped discharge. 

9 The piped discharge from the detention area is to connect directly to the street 

drainage system where possible. However other discharge locations may be 

considered. 

6.10 INTERALLOTMENT DRAINAGE 

1 Interallotment Drainage shall be provided in new subdivisions for every allotment, 

which does not drain directly to its street frontage. 

2 Interallotment drainage shall be contained within an easement not less than 1.0m 

wide, and the easement shall be in favour of the benefiting allotments. 

3 Pipe Capacity – The interallotment drain shall be designed to accept concentrated 

drainage from buildings and paved areas on each allotment for flow rates having a 

design ARI of 100 years. 

4 In lieu of more detailed analysis, the following areas of impervious surface are 

assumed to be contributing runoff to the interallotment drain:- 

Development Type 

Minimum % of Lot Area 

• Residential (2a) and (2b) 60 

• Industrial/ Commercial 90 

5 Pipes shall be a minimum diameter of 150mm and designed to flow full at the 

design discharge without surcharging of pits. Consideration shall be given where 

connections are proposed to other systems designed under pressure. 

6 Pipes shall have a minimum cover of 300mm, ensuring that it serves the total lot, 

taking into consideration future site regrading of terracing of lots. 

56 



7 Pipes – Minimum Grade – The interallotment drainage system shall have a 

desirable minimum longitudinal grade of 1%. 

8 Interallotment Drainage Pipe – Relationship to Sewer Mains – Where 

interallotment drainage and sewer mains are laid adjacent and parallel to each 

other they are to be spaced 0.75 metres between pipe centrelines unless pipelines 

are greater than 300mm diameter where the minimum clearance between pipes 

shall be 450mm. The sewer shall be located closest to the dwelling being served. 

9 Interallotment drainage shall be required for high side properties fronting roads 

with either kerbing unable to satisfactorily accommodate kerb outlets or with one 

way cross fall. 

10 Existing lots that discharge stormwater onto proposed developments shall be 

provided with either: 

i 

ii 

iii 

An interallotment drainage system within the existing properties as 

detailed herein. This will necessitate the creation of drainage easements 

and negotiations by the Developer; or 

An interallotment drainage system within the proposed development and 

the provision of pipe stubs into each adjoining lot. This will necessitate 

the creation of easements in favour of the existing properties. 

All works shall be to the satisfaction of the existing owners and at full cost 

to the Developer. 

11 No development will be permitted over interallotment drainage easements. 

12 Impervious areas draining to interallotment drainage systems are not to be 

excluded from the street drainage collection catchment. This requirement is to 

ensure full collection of stormwater prior to the fully development site where 

impervious areas are connected to the interallotment drainage 

6.10.1 Interallotment Drainage Pits 

1 Interallotment drainage pits shall be provided to the low corner of each lot 

unless otherwise approved. The minimum pit sizes shall be in 

accordance with the table found in Appendix M. 

2 Pits will also be provided at changes of pipe size, changes in grade, 

changes in pipe type or class, and changes in direction. 

3 In situations where an interallotment drainage line traverses 3 lots without 

a change in pipe size, grade, pipe type or class, or change in direction, a 

slope junction with an inspection opening may be permitted on the low 

corner of the intermediate lot. 

4 Pit inlets shall be in accordance with Appendix M. Pit surrounds will be 

57 



turfed and pegged or netted to a minimum width of 900mm to provide 

adequate scour protection. 

5 Step irons are to be provided in all pits with a depth of 1.2 metres and 

over. 

6 Connection for roof water for single residential dwellings shall be provided 

via a minimum 100mm dia stub into the side of the pit. 

6.11 CONDUITS, LOCATION AND COVER 

1 Pipe Bedding and Cover – Requirements shall be determined from the Concrete 

Pipe Association of Australia “Concrete Pipe Selection and Installation” or AS 3725 

Loads on Buried Pipes. 

2 Drainage lines in road reserves shall generally be located such that the boundary 

edge of the culvert is under the face of kerb and the culvert extends under the road 

pavement and parallel to the kerb. 

3 Drainage lines in easements shall generally be centrally located within easements. 

6.12 EASEMENTS 

6.12.1 Easement Widths 

Easements to drain water are to be created over all pipelines. The width of 

easement depends upon the diameter of the pipeline, and is given in the table 

below, 

Pipe Diameter (mm) Easement Width (m) 

Less than 600 2.5 

600 to 900 3.0 

1050 to 1200 3.5 

1350 to 1500 4.0 

1650 to 1800 4.5 

Greater than 1800 

Pipe diameter plus 1m rounded to the next 

0.5m 

For multiple pipes and box culvert a minimum clearance of 500mm is required 

between each culvert and the edge of the easement. The easement width is to 

increase at 500mm increments. 

The above easement widths will necessitate widening where excessive pipe 

depths occur. 

All pipes are to be laid centrally within the designated easement. 

Interallotment drainage easements shall be created in favour of the benefiting 

properties. 

58 



All other easements shall be in favour of Council unless advised otherwise. 

59 



6.12.2 Building Adjacent to Easements 

1 Building over Council or interallotment drainage easements is prohibited. 

However Council may consider applications for buildings over 

interallotment drainage easements on the merits of each individual case. 

Reference should be made to Council’s “Guidelines for Building Adjacent 

to a Drainage Easement”. 

2 Where an overland flow path exists or is proposed over a drainage 

easement, structures of any type will not be permitted. Generally the lot 

title will have restrictions placed upon it ensuring that the overland flow 

path levels are maintained as constructed and no structures are erected 

within the flow path. 

3 In cases where a building adjoins an open lined or unlined stormwater 

channel, conditions will be imposed in accordance with Council’s Setback 

Policy. 

4 Where a building adjoins an easement with a piped system: The depth of 

the footing at the boundary of the drainage easement is to be level with 

the invert of the piped drain as a minimum. The footing depth may 

decrease by 500mm for every 1m increment in distance from the edge of 

easement depending on soil types. Reference should be made to 

Council’s “Guidelines for Building Adjacent to a Drainage Easement”. 

5 Where a building is proposed within the zone of influence of a drainage 

easement then details of the design piers, beams and footings prepared 

by a qualified civil (or structural) engineer shall be submitted for approval 

with the application. Certification of the design and construction is to be 

submitted by the consulting Engineer. 

6 Council discourages concrete driveways over easements. Block paving or 

bitumen seal are preferred alternatives. 

7 Generally filling or piping of open channels will not be permitted. However 

if an applicant requests Council to consider filling or piping of open 

channels then approval in principal must be obtained from the DIPNR 

prior to submission of an application to Council. 

8 In cases where a watercourse or drainage structure is not covered by 

easement rights, an easement in favour of Council shall be created over 

the drainage works prior to the release of building plans. 

60 



6.13 STORMWATER DISCHARGE 

1 Scour protection and energy dissipation structures shall be provided at all drainage 

outlets in accordance with the approved engineering plans and current best 

industry practice. 

2 At points of discharge of gutters or stormwater drainage lines or at any 

concentration of stormwater from or to adjoining properties, Council will require the 

Developer to enter into a Deed of Agreement with the adjoining owner(s) granting 

permission to the discharge of stormwater drainage and the creation of any 

necessary easements with all costs being met by the Developer prior to 

development approval. 

3 Where the drainage is to discharge to an area under the control of another 

statutory authority eg, DIPNR, the design requirements of that Statutory Authority 

are also to be met. 

4 Piped stormwater drainage discharging to or through recreation reserves, if 

permitted under the relevant plan of management, is to be taken to a natural water 

course and discharged through an approved outlet structure or alternatively taken 

to the nearest stormwater drainage line. The creation of easements will be 

required. 

5 Suitable approved safety fencing maybe required at the outlet point. 

6 Where no road pipe drainage system exists, the maximum permissible site 

discharge from a development to either the kerb and gutter or table drain shall be 

30 litres/sec unless otherwise advised by the Engineer. 

61 



6.14 MISCELLANEOUS 

6.14.1 Trench stops and Bulkheads 

The provision of trench stops or bulkheads will be required at maximum 3.6m 

centres where the pipe grade exceeds 20%. The bulkhead shall be rebated into 

the bottom and sides of the trench for at least 150mm. 

6.14.2 Subsoil Drainage 

Subsoil drainage in Pipe Trenches – Subsoil Drainage shall be provided in pipe 

trenches as outlined below. 

1 In cases where pipe trenches are backfilled with sand or other pervious 

material, a 3.0m length of subsoil drain shall be provided in the bottom of 

the trench immediately upstream from each pit or headwall. 

2 The upstream end of the subsoil drain shall be sealed with cement mortar 

or other approved means, and the downstream end shall discharge 

through the wall of the pit or headwalls. The outlet shall be provided with 

galvanised mesh to prevent vermin access. 

6.14.3 Kerb and Gutter Discharge 

Termination of Kerb and Gutter and Associated Scour Protection – Kerb and 

Gutter shall be extended to a drainage pit or approved natural point of outlet. At 

the kerb and gutter discharge point approved scour protection shall be provided 

of length and type sufficiently adequate to cater for design flows. 

6.14.4 Habitable Floor Levels 

Floor levels should be a minimum 500mm above the surrounding ground levels 

to negate the possibility of street stormwater and overland sheet flows entering 

dwellings. 

Minimum floor levels may be required where a property is located within a 1% 

AEP floodplain. Enquires can be made to Council to confirm floor level 

requirements. 

62 



6.15 DOCUMENTATION 

6.15.1 Easements and Agreements 

1 Evidence of any Deed of Agreement necessary to be entered into as part 

of the drainage system will need to be submitted to the Engineer prior to 

any approval of the engineering plans. Easements will need to be created 

prior to approval of the linen plan of subdivision. 

2 Where an agreement is reached with an adjacent landowner to increase 

flood levels on his property or otherwise adversely affect his property, a 

letter signed by all the landowners outlining what they have agreed to and 

witnessed by an independent person shall be submitted to the Engineer 

prior to any approval of the engineering plans. 

6.16 STORMWATER QUALITY 

All developments shall ensure that stormwater discharge from the site satisfies 

environmental requirements by way of restricting increases in pollutants during and post 

construction. 

In areas that are controlled by regional constructed wetlands, at source treatment is 

required to carry out the initial cleansing of stormwater by targeting suspended solids, 

litter, coarse sediments and where specific pollutants are generated by the nature of the 

catchment, such as hydrocarbons, heavy metals and litter from car parks, specific 

treatments shall be provided. 

Manufacturers details for particular devices should include all relevant information on 

pollutants they treat, flow rates (treatable flows), percentage removal of the targeted 

pollutants. 

In areas without such facilities a constructed wetland designed in accordance with 

Council’s requirements shall be provided. 

Where the end of pipe treatment is only required to trap gross pollutants, an approved 

underground, easily maintained precast device shall generally be required. The sizing of 

the device is to be as designed by the manufacturers technical experts. 

Where the facility is required to be a constructed wetland the size shall be determined in 

accordance with Chapter 16.3 of the DIPNR Constructed Wetlands Manual. 

Other treatment devices will be considered on merit and the design consultant is 

encouraged to actively seek out any advancement of knowledge in the stormwater 

pollution treatment area. 

The proximity and sensitivity of the receiving waters will also play a significant role in the 

type/s of stormwater quality treatments required. 

Where appropriate, roads and driveways shall be designed to incorporate swales with 

appropriate capacities in lieu of kerb and guttering but should not be used where: 

63 



• On-street parking is required or the area is subject to high use. 

• Roads and driveways have numerous accesses. 

• Insitu soils have high clay content or are susceptible to heavy compaction. 

• Roads area either less than 1% grade and greater than 5% or where catchments 

are greater than 2 ha. 

Advice should be sought from Consultants who are adequately experienced and are 

aware of the rapidly expanding knowledge being gained in this relatively new field 

regarding initial planning and detail design. 

6.17 MAINTENANCE PLAN 

A Maintenance Plan is required for all new major systems to ensure the necessary 

maintenance requirements are identified so that the system can be cost effectively 

maintained to the design capacity and ensure the design flows can be accommodated.. 

The aim of a maintenance plan is to outline tasks required to contain flood flows 

within the nominated flow path and to maintain flood levels pertaining to a 1% AEP 

flood event. Some of the issues to be considered include, 

• Maintaining the design cross sectional area required for the design flow, 

• Maintaining the design coefficient of friction adopted, 

• Protection of flora and fauna, 

• Protection and rehabilitation of riparian zones, 

• Weed control, 

• Visual impact, 

• Community concerns, 

• To quantify the associated maintenance cost 

A part 5 Environmental Assessment is to be undertaken for the initial construction and 

ongoing maintenance works. This information and any related work procedures are to 

be included in the final plan. 

For practical purposes the document is to provide field instructions for maintenance 

staff to enable them to clearly identify works to be undertaken. It is therefore 

important that the ongoing maintenance plan is a stand-alone document that can be 

readily used by maintenance staff in the field. 

The methods used to maintain the cross sectional area are to be researched and 

specified. These methods are to be shown to comply with any environmental or 

regulatory requirements 

64 



Appendix 

Appendix 

Page 

A Standard Line types and Symbols. 63 

B Stormwater Drainage Calculations Sheet. 64 

C Maximum Access Profiles 65-67 

D Time Of Flow In Gutter .Fig D1 68 

E Rainfall Intensity Zones 

Rainfall Intensity Zones Map fig E1 69 

Urban Run Off Coefficient Fig E2 70 

Rainfall Intensity Values Up to 60 Min 

Terrigal Table E1 71 

Woy Woy Table E2 72 

Mangrove Creek Dam Table E3 73 

Peats Ridge Table E4 74 

Narara Table E5 75 

Rainfall Intensity Values Up to 72 Hrs 






Rainfall Duration Intensity Values Up to 60 Min 






F Maximum Permissible Gutter Flow 86 

G Kerb Inlet Capacities 87 

H Pressure Head Change Coefficients 88-95 

I Velocity and Discharge Diagram 96 

J Minimum HGL outlet control levels 97 

K Percentage Impervious for various Zoning Areas 98 

L Velocity and Depth Relationships 99 

M Interallotment Pit Schedule 100 

N Standards and Guidelines 101-102 

N Stormwater Drainage Calculation Form Details 104-115 

65 



Appendix A 

STANDARD LINE TYPES AND SYMBOLS 

66 



STORMWATER DRAINAGE CALCULATION FORM 

Appendix B 

67 



ACCESS PROFILE ABOVE ROAD 

FOR RTA STANDARD CAR 130MM CLEARANCE 

Appendix C 

68 



ACCESS PROFILE BELOW ROAD 

FOR RTA STANDARD CAR 130MM CLEARANCE 

Appendix C 

Note :- When maximum roll over and grades are used the gutter depth of flow is reduced to 100mm. 

Storm water flows may over top the access and must be catered for in the access design by providing a 

kerb inlet pit upstream of the access or providing drainage collection within the property. 

69 



Appendix C 

MAXIMUM ACCESS PROFILE FOR NEW SUBDIVISIONS 

70 



Appendix D 

TIME OF FLOW IN GUTTER 

71 



Figure E1- RAINFALL INTENSITY ZONES 

Appendix E 

72 



Appendix E 

Figure E2 - URBAN COEFFICIENT OF RUNOFF C10 

73 


Version 3 (January 2004) 

74 


Appendix E 

TABLE E1 - RAINFALL INTENSITY (mm/hr) FOR TERRIGAL 

Minutes 1 Year 2 Years 5 Years 10 Years 20 Years 50 Years 100 Years 

6 

7 

8 

9 

10 

11 

12 

13 

14 

15 

16 

17 

18 

19 

20 

21 

22 

23 

24 

25 

26 

27 

28 

29 

30 

31 

32 

33 

34 

35 

36 

37 

38 

39 

40 

41 

42 

43 

44 

45 

46 

47 

48 

49 

50 

51 

52 

53 

54 

55 

56 

57 

58 

59 

60 

101 

95 

91 

86 

83 

80 

77 

74 

72 

70 

68 

66 

64 

62 

61 

60 

58 

57 

56 

55 

54 

53 

52 

51 

50 

49 

48 

47 

46 

46 

45 

44 

44 

43 

42 

42 

41 

41 

40 

40 

39 

39 

38 

38 

37 

37 

37 

36 

36 

35 

35 

35 

34 

34 

34 

128 

121 

115 

110 

105 

101 

98 

94 

91 

89 

86 

84 

82 

80 

78 

76 

74 

73 

71 

70 

69 

67 

66 

65 

64 

63 

62 

61 

60 

59 

58 

57 

56 

55 

55 

54 

53 

52 

52 

51 

50 

50 

49 

49 

48 

47 

47 

46 

46 

45 

45 

44 

44 

44 

43 

158 

150 

142 

136 

131 

126 

122 

118 

114 

111 

108 

105 

103 

100 

98 

96 

94 

92 

90 

88 

86 

85 

83 

82 

81 

79 

78 

77 

76 

74 

73 

72 

71 

70 

69 

68 

67 

67 

66 

65 

64 

63 

63 

62 

61 

61 

60 

59 

59 

58 

57 

57 

56 

56 

55 

175 

165 

157 

151 

145 

140 

135 

131 

127 

123 

120 

117 

114 

112 

109 

107 

104 

102 

100 

98 

97 

95 

93 

92 

90 

89 

87 

86 

85 

83 

82 

81 

80 

79 

78 

77 

76 

75 

74 

73 

72 

71 

70 

70 

69 

68 

67 

67 

66 

65 

64 

64 

63 

63 

62 

197 

187 

178 

171 

164 

158 

153 

149 

144 

140 

137 

133 

130 

127 

124 

122 

119 

117 

115 

112 

110 

108 

107 

105 

103 

101 

100 

98 

97 

95 

94 

93 

91 

90 

89 

88 

87 

86 

85 

84 

83 

82 

81 

80 

79 

78 

77 

76 

76 

75 

74 

73 

73 

72 

71 

226 

215 

205 

196 

189 

183 

177 

171 

166 

162 

158 

154 

150 

147 

144 

141 

138 

135 

133 

130 

128 

126 

124 

122 

120 

118 

116 

114 

113 

111 

109 

108 

106 

105 

104 

102 

101 

100 

99 

97 

96 

95 

94 

93 

92 

91 

90 

89 

88 

87 

86 

85 

85 

84 

83 

248 

236 

225 

216 

208 

201 

194 

189 

183 

178 

174 

170 

166 

162 

159 

155 

152 

149 

147 

144 

141 

139 

137 

134 

132 

130 

128 

126 

125 

123 

121 

119 

118 

116 

115 

113 

112 

111 

109 

108 

107 

105 

104 

103 

102 

101 

100 

99 

98 

97 

96 

95 

94 

93 

92


75 


Appendix E 

TABLE E2 - RAINFALL INTENSITY (mm/hr) FOR WOY WOY 


6 

7 

8 

9 

10 

11 

12 

13 

14 

15 

16 

17 

18 

19 

20 

21 

22 

23 

24 

25 

26 

27 

28 

29 

30 

31 

32 

33 

34 

35 

36 

37 

38 

39 

40 

41 

42 

43 

44 

45 

46 

47 

48 

49 

50 

51 

52 

53 

54 

55 

56 

57 

58 

59 

60 

87 

83 

78 

75 

72 

69 

66 

64 

62 

60 

58 

57 

55 

54 

52 

51 

50 

49 

48 

47 

46 

45 

44 

43 

43 

42 

41 

40 

40 

39 

39 

38 

37 

37 

36 

36 

35 

35 

35 

34 

34 

33 

33 

32 

32 

32 

31 

31 

31 

30 

30 

30 

30 

29 

29 

112 

106 

100 

96 

92 

88 

85 

82 

79 

77 

75 

73 

71 

69 

67 

66 

64 

63 

61 

60 

59 

58 

57 

56 

55 

54 

53 

52 

51 

50 

50 

49 

48 

48 

47 

46 

46 

45 

44 

44 

43 

43 

42 

42 

41 

41 

40 

40 

40 

39 

39 

38 

38 

38 

37 

141 

134 

127 

122 

116 

112 

108 

104 

101 

98 

95 

93 

90 

88 

86 

84 

82 

80 

79 

77 

75 

74 

73 

71 

70 

69 

68 

67 

66 

65 

64 

63 

62 

61 

60 

60 

59 

58 

57 

57 

56 

55 

55 

54 

53 

53 

52 

52 

51 

51 

50 

50 

49 

49 

48 

158 

150 

142 

136 

131 

126 

121 

117 

113 

110 

107 

104 

101 

99 

97 

94 

92 

90 

88 

87 

85 

83 

82 

81 

79 

78 

77 

75 

74 

73 

72 

71 

70 

69 

68 

67 

66 

66 

65 

64 

63 

62 

62 

61 

60 

60 

59 

58 

58 

57 

57 

56 

56 

55 

55 

181 

171 

163 

156 

149 

144 

139 

134 

130 

126 

123 

119 

116 

113 

111 

108 

106 

104 

102 

100 

98 

96 

94 

93 

91 

89 

88 

87 

85 

84 

83 

82 

81 

79 

78 

77 

76 

75 

75 

74 

73 

72 

71 

70 

70 

69 

68 

67 

67 

66 

65 

65 

64 

64 

63 

210 

199 

189 

181 

174 

167 

162 

156 

152 

147 

143 

139 

136 

132 

129 

126 

124 

121 

119 

116 

114 

112 

110 

108 

106 

105 

103 

101 

100 

98 

97 

96 

94 

93 

92 

91 

90 

88 

87 

86 

85 

84 

83 

83 

82 

81 

80 

79 

78 

78 

77 

76 

75 

75 

74 

232 

220 

210 

200 

192 

185 

179 

173 

168 

163 

158 

154 

150 

147 

143 

140 

137 

134 

132 

129 

127 

124 

122 

120 

118 

116 

114 

113 

111 

109 

108 

106 

105 

103 

102 

101 

100 

98 

97 

96 

95 

94 

93 

92 

91 

90 

89 

88 

87 

86 

85 

85 

84 

83 

82


76 


Appendix E 

TABLE E3 - RAINFALL INTENSITY (mm/hr) FOR MANGROVE CREEK DAM 


6 

7 

8 

9 

10 

11 

12 

13 

14 

15 

16 

17 

18 

19 

20 

21 

22 

23 

24 

25 

26 

27 

28 

29 

30 

31 

32 

33 

34 

35 

36 

37 

38 

39 

40 

41 

42 

43 

44 

45 

46 

47 

48 

49 

50 

51 

52 

53 

54 

55 

56 

57 

58 

59 

60 

72 

68 

64 

61 

59 

56 

54 

52 

51 

49 

48 

46 

45 

44 

43 

42 

41 

40 

39 

38 

37 

37 

36 

35 

35 

34 

33 

33 

32 

32 

31 

31 

30 

30 

30 

29 

29 

28 

28 

28 

27 

27 

27 

26 

26 

26 

26 

25 

25 

25 

25 

24 

24 

24 

24 

93 

88 

83 

79 

76 

73 

70 

68 

65 

63 

61 

60 

58 

56 

55 

54 

52 

51 

50 

49 

48 

47 

46 

45 

45 

44 

43 

42 

42 

41 

40 

40 

39 

39 

38 

38 

37 

37 

36 

36 

35 

35 

34 

34 

34 

33 

33 

33 

32 

32 

32 

31 

31 

31 

30 

120 

113 

107 

102 

98 

94 

90 

87 

84 

81 

79 

77 

74 

72 

71 

69 

67 

66 

64 

63 

62 

60 

59 

58 

57 

56 

55 

54 

53 

53 

52 

51 

50 

50 

49 

48 

48 

47 

46 

46 

45 

45 

44 

44 

43 

43 

42 

42 

41 

41 

41 

40 

40 

39 

39 

136 

128 

122 

116 

111 

106 

102 

98 

95 

92 

89 

86 

84 

82 

80 

78 

76 

74 

73 

71 

70 

68 

67 

66 

65 

63 

62 

61 

60 

59 

58 

58 

57 

56 

55 

54 

54 

53 

52 

52 

51 

51 

50 

49 

49 

48 

48 

47 

47 

46 

46 

45 

45 

45 

44 

156 

148 

140 

134 

128 

122 

118 

113 

110 

106 

103 

100 

97 

94 

92 

90 

87 

85 

84 

82 

80 

79 

77 

76 

74 

73 

72 

71 

69 

68 

67 

66 

65 

64 

64 

63 

62 

61 

60 

60 

59 

58 

58 

57 

56 

56 

55 

54 

54 

53 

53 

52 

52 

51 

51 

185 

174 

165 

157 

150 

144 

138 

133 

129 

125 

121 

117 

114 

111 

108 

105 

103 

100 

98 

96 

94 

92 

90 

89 

87 

86 

84 

83 

81 

80 

79 

78 

77 

76 

75 

74 

73 

72 

71 

70 

69 

68 

67 

67 

66 

65 

65 

64 

63 

63 

62 

61 

61 

60 

60 

206 

194 

184 

176 

168 

161 

154 

149 

143 

139 

134 

130 

127 

123 

120 

117 

114 

112 

109 

107 

105 

103 

101 

99 

97 

95 

94 

92 

91 

89 

88 

87 

85 

84 

83 

82 

81 

80 

79 

78 

77 

76 

75 

74 

73 

73 

72 

71 

70 

70 

69 

68 

68 

67 

66


77 


Appendix E 

TABLE E4 - RAINFALL INTENSITY (mm/hr) FOR PEATS RIDGE 


6 

7 

8 

9 

10 

11 

12 

13 

14 

15 

16 

17 

18 

19 

20 

21 

22 

23 

24 

25 

26 

27 

28 

29 

30 

31 

32 

33 

34 

35 

36 

37 

38 

39 

40 

41 

42 

43 

44 

45 

46 

47 

48 

49 

50 

81 

77 

73 

70 

67 

64 

61 

59 

57 

55 

54 

52 

51 

49 

48 

47 

46 

45 

44 

43 

42 

41 

41 

40 

39 

39 

38 

37 

37 

36 

36 

35 

35 

34 

34 

33 

33 

32 

32 

32 

31 

31 

30 

30 

30 

104 

98 

93 

89 

85 

82 

79 

76 

73 

71 

69 

67 

65 

63 

62 

60 

59 

58 

56 

55 

54 

53 

52 

51 

50 

49 

49 

48 

47 

46 

46 

45 

44 

44 

43 

42 

42 

41 

41 

40 

40 

39 

39 

39 

38 

131 

124 

118 

112 

107 

103 

99 

96 

92 

90 

87 

84 

82 

80 

78 

76 

74 

73 

71 

70 

68 

67 

66 

64 

63 

62 

61 

60 

59 

58 

58 

57 

56 

55 

54 

54 

53 

52 

52 

51 

51 

50 

49 

49 

48 

147 

139 

132 

126 

120 

115 

111 

107 

103 

100 

97 

94 

92 

89 

87 

85 

83 

81 

80 

78 

76 

75 

73 

72 

71 

70 

69 

67 

66 

65 

64 

64 

63 

62 

61 

60 

59 

59 

58 

57 

57 

56 

55 

55 

54 

167 

158 

151 

144 

137 

132 

127 

122 

118 

114 

111 

108 

105 

102 

100 

97 

95 

93 

91 

89 

87 

86 

84 

82 

81 

80 

78 

77 

76 

75 

74 

73 

72 

71 

70 

69 

68 

67 

66 

65 

65 

64 

63 

63 

62 

195 

184 

175 

167 

160 

153 

147 

142 

137 

133 

129 

125 

122 

119 

116 

113 

110 

108 

106 

103 

101 

99 

98 

96 

94 

93 

91 

90 

88 

87 

86 

84 

83 

82 

81 

80 

79 

78 

77 

76 

75 

74 

74 

73 

72 

215 

203 

193 

184 

176 

169 

163 

157 

152 

147 

143 

139 

135 

131 

128 

125 

122 

119 

117 

114 

112 

110 

108 

106 

104 

102 

101 

99 

98 

96 

95 

93 

92 

91 

90 

88 

87 

86 

85 

84 

83 

82 

81 

80 

80


78 


Appendix E 

TABLE E5 - RAINFALL INTENSITY (mm/hr) FOR NARARA 


6 

7 

8 

9 

10 

11 

12 

13 

14 

15 

16 

17 

18 

19 

20 

21 

22 

23 

24 

25 

26 

27 

28 

29 

30 

31 

32 

33 

34 

35 

36 

37 

38 

39 

40 

41 

42 

43 

44 

45 

46 

47 

48 

49 

50 

51 

52 

53 

54 

55 

56 

57 

58 

59 

60 

89 

84 

79 

76 

73 

70 

67 

65 

63 

61 

59 

57 

56 

54 

53 

52 

50 

49 

48 

47 

46 

45 

45 

44 

43 

42 

42 

41 

40 

40 

39 

38 

38 

37 

37 

36 

36 

35 

35 

35 

34 

34 

33 

33 

33 

32 

32 

32 

31 

31 

31 

30 

30 

30 

29 

113 

106 

101 

96 

92 

89 

85 

82 

80 

77 

75 

73 

71 

69 

67 

66 

64 

63 

62 

60 

59 

58 

57 

56 

55 

54 

53 

52 

51 

51 

50 

49 

48 

48 

47 

47 

46 

45 

45 

44 

44 

43 

43 

42 

42 

41 

41 

40 

40 

40 

39 

39 

38 

38 

38 

142 

134 

127 

121 

116 

111 

107 

104 

100 

97 

94 

92 

89 

87 

85 

83 

81 

79 

78 

76 

75 

73 

72 

70 

69 

68 

67 

66 

65 

64 

63 

62 

61 

60 

60 

59 

58 

57 

57 

56 

55 

55 

54 

53 

53 

52 

52 

51 

51 

50 

50 

49 

49 

48 

48 

156 

148 

141 

134 

129 

124 

119 

115 

112 

108 

105 

102 

99 

97 

95 

92 

90 

88 

87 

85 

83 

82 

80 

79 

77 

76 

75 

74 

73 

71 

70 

69 

68 

68 

67 

66 

65 

64 

63 

63 

62 

61 

60 

60 

59 

58 

58 

57 

57 

56 

56 

55 

55 

54 

54 

176 

167 

159 

152 

146 

140 

135 

131 

127 

123 

119 

116 

113 

110 

108 

105 

103 

101 

99 

97 

95 

93 

91 

90 

88 

87 

85 

84 

83 

82 

80 

79 

78 

77 

76 

75 

74 

73 

72 

71 

71 

70 

69 

68 

68 

67 

66 

65 

65 

64 

64 

63 

62 

62 

61 

205 

194 

185 

177 

169 

163 

157 

152 

147 

142 

138 

135 

131 

128 

125 

122 

119 

117 

114 

112 

110 

108 

106 

104 

102 

101 

99 

97 

96 

95 

93 

92 

91 

89 

88 

87 

86 

85 

84 

83 

82 

81 

80 

79 

78 

78 

77 

76 

75 

75 

74 

73 

72 

72 

71 

226 

214 

204 

195 

187 

179 

176 

167 

162 

157 

153 

148 

145 

141 

138 

134 

132 

129 

126 

124 

121 

119 

117 

115 

113 

111 

109 

108 

106 

104 

103 

102 

100 

99 

98 

96 

95 

94 

93 

92 

91 

90 

89 

88 

87 

86 

85 

84 

83 

83 

82 

81 

80 

79 

79


TABLE E6 - RAINFALL INTENSITY – DURATION RETURN PERIOD FOR TERRIGAL 

Appendix E 

79 



TABLE E7 - RAINFALL INTENSITY – DURATION – RETURN PERIOD FOR WOY WOY 

Appendix E 

80 



TABLE E8 – 

RAINFALL INTENSITY – DURATION – RETURN PERIOD FOR MANGROVE CREEK DAM 

Appendix E 

81 



Appendix E 

TABLE E9 - RAINFALL INTENSITY – DURATION – RETURN PERIOD FOR PEATS RIDGE 

82 



TABLE E10 - RAINFALL INTENSITY – DURATION – RETURN PERIOD FOR NARARA 

Appendix E 

83 



84 


Appendix E 

TABLE E11 - RAINFALL DURATION INTENSITY (min mm/hr) FOR TERRIGAL (t.I 0.4 ) 

DURATION 

AVERAGE RECURRENCE INTERVAL 


6 

7 

8 

9 

10 

11 

12 

13 

14 

15 

16 

17 

18 

19 

20 

21 

22 

23 

24 

25 

26 

27 

28 

29 

30 

31 

32 

33 

34 

35 

36 

37 

38 

39 

40 

41 

42 

43 

44 

45 

46 

47 

48 

49 

50 

51 

52 

53 

54 

55 

56 

57 

58 

59 

60 

38.0 

43.3 

48.6 

53.5 

58.6 

63.5 

68.2 

72.4 

77.5 

82.1 

86.5 

90.8 

95.0 

99.0 

103.6 

108.0 

111.6 

115.9 

120.1 

124.2 

128.2 

132.2 

136.0 

139.8 

143.5 

147.0 

150.5 

153.9 

157.2 

161.9 

165.0 

168.1 

172.6 

175.6 

178.4 

182.8 

185.5 

189.9 

192.4 

196.8 

199.2 

203.5 

205.7 

209.9 

212.0 

216.2 

220.4 

222.2 

226.4 

228.0 

232.2 

236.3 

237.7 

241.8 

245.9 

41.8 

47.7 

53.4 

59.0 

64.3 

69.7 

75.1 

80.0 

85.1 

90.3 

95.0 

100.0 

104.9 

109.6 

114.3 

118.7 

123.1 

128.0 

132.0 

136.8 

141.4 

145.1 

149.6 

154.0 

158.3 

162.6 

166.8 

170.9 

174.9 

178.8 

182.7 

186.4 

190.1 

193.7 

198.7 

202.2 

205.6 

208.9 

213.7 

216.9 

220.0 

224.7 

227.7 

232.4 

235.2 

237.9 

242.6 

245.1 

249.7 

252.1 

256.7 

259.0 

263.5 

268.1 

270.1 

45.5 

51.9 

58.1 

64.2 

70.3 

76.1 

82.0 

87.6 

93.1 

98.7 

104.1 

109.4 

114.9 

119.9 

125.2 

130.4 

135.4 

140.4 

145.2 

149.9 

154.4 

159.6 

164.0 

169.0 

174.0 

178.0 

182.8 

187.5 

192.2 

195.8 

200.3 

204.7 

209.1 

213.4 

217.6 

221.7 

225.8 

231.2 

235.1 

239.0 

242.8 

246.5 

251.8 

255.4 

258.9 

264.1 

267.5 

270.8 

275.9 

279.1 

282.2 

287.2 

290.2 

295.2 

298.1 

47.4 

54.0 

60.5 

67.0 

73.2 

79.4 

85.4 

91.4 

97.2 

102.8 

108.6 

114.2 

119.7 

125.4 

130.6 

136.1 

141.0 

146.3 

151.4 

156.5 

162.1 

166.9 

171.6 

177.0 

181.5 

186.7 

191.0 

196.0 

201.0 

205.0 

209.8 

214.6 

219.3 

223.9 

228.5 

233.0 

237.5 

241.8 

246.1 

250.3 

254.5 

258.6 

262.6 

268.1 

272.0 

275.8 

279.5 

284.9 

288.5 

292.1 

295.6 

300.8 

304.2 

309.4 

312.7 

49.7 

56.7 

63.6 

70.4 

76.9 

83.3 

89.8 

96.2 

102.2 

108.3 

114.5 

120.2 

126.1 

131.9 

137.5 

143.5 

148.8 

154.5 

160.1 

165.1 

170.4 

175.7 

181.5 

186.6 

191.5 

196.4 

201.9 

206.5 

211.9 

216.4 

221.6 

226.8 

230.9 

235.9 

240.9 

245.8 

250.6 

255.4 

260.1 

264.8 

269.4 

273.9 

278.4 

282.8 

287.1 

291.3 

295.5 

299.6 

305.3 

309.3 

313.2 

317.1 

322.7 

326.4 

330.1 

52.5 

60.0 

67.3 

74.3 

81.4 

88.4 

95.1 

101.7 

108.2 

114.8 

121.2 

127.5 

133.6 

139.9 

146.0 

152.0 

157.9 

163.6 

169.7 

175.2 

181.1 

186.9 

192.5 

198.1 

203.6 

209.0 

214.3 

219.4 

225.3 

230.2 

235.1 

240.8 

245.4 

250.9 

256.4 

260.7 

266.1 

271.3 

276.5 

280.5 

285.5 

290.5 

295.5 

300.3 

305.1 

309.9 

314.6 

319.2 

323.7 

328.2 

332.6 

337.0 

342.9 

347.2 

351.4 

54.4 

62.3 

69.8 

77.3 

84.6 

91.8 

98.7 

105.8 

112.5 

119.2 

126.0 

132.6 

139.1 

145.4 

151.9 

157.9 

164.1 

170.2 

176.7 

182.5 

188.2 

194.3 

200.4 

205.7 

211.5 

217.2 

222.9 

228.4 

234.6 

239.9 

245.1 

250.3 

256.2 

261.1 

266.9 

271.7 

277.3 

282.9 

287.4 

292.8 

298.2 

302.4 

307.6 

312.8 

318.0 

323.1 

328.1 

333.1 

338.0 

342.8 

347.6 

352.3 

357.0 

361.6 

366.2


85 


Appendix E 

TABLE E12 - RAINFALL DURATION INTENSITY (min mm/hr) FOR WOY WOY (t.I 0.4 ) 

Minutes 

1 

Year 

2 

Years 

5 

Years 

10 

Years 

20 

Years 

50 

Years 

100 

Years 

6 

7 

8 

9 

10 

11 

12 

13 

14 

15 

16 

17 

18 

19 

20 

21 

22 

23 

24 

25 

26 

27 

28 

29 

30 

31 

32 

33 

34 

35 

36 

37 

38 

39 

40 

41 

42 

43 

44 

45 

46 

47 

48 

49 

50 

51 

52 

53 

54 

55 

56 

57 

58 

59 

60 

35.8 

41.0 

45.7 

50.6 

55.3 

59.8 

64.1 

68.6 

73.0 

77.2 

81.2 

85.7 

89.4 

93.7 

97.1 

101.2 

105.2 

109.1 

112.9 

116.6 

120.2 

123.8 

127.2 

130.6 

135.1 

138.2 

141.3 

144.3 

148.7 

151.5 

155.9 

158.5 

161.1 

165.3 

167.7 

171.9 

174.1 

178.3 

182.4 

184.4 

188.5 

190.3 

194.4 

196.0 

200.0 

204.0 

205.4 

209.3 

213.3 

214.4 

218.3 

222.2 

226.1 

226.9 

230.7 

39.6 

45.2 

50.5 

55.9 

61.0 

65.9 

70.9 

75.8 

80.4 

85.2 

90.0 

94.6 

99.0 

103.3 

107.5 

112.2 

116.1 

120.6 

124.3 

128.6 

132.8 

137.0 

141.1 

145.1 

149.0 

152.9 

156.6 

160.3 

163.9 

167.4 

172.1 

175.5 

178.8 

183.5 

186.6 

189.6 

194.2 

197.1 

199.9 

204.5 

207.1 

211.6 

214.1 

218.5 

220.8 

225.3 

227.4 

231.8 

236.2 

238.1 

242.4 

244.2 

248.5 

252.8 

254.4 

43.4 

49.7 

55.5 

61.5 

67.0 

72.6 

78.1 

83.3 

88.7 

93.9 

98.9 

104.2 

108.9 

113.9 

118.8 

123.6 

128.2 

132.7 

137.8 

142.1 

146.2 

151.0 

155.8 

159.6 

164.1 

168.6 

173.0 

177.4 

181.7 

185.9 

190.0 

194.1 

198.0 

201.9 

205.7 

210.9 

214.6 

218.2 

221.7 

226.8 

230.2 

233.5 

238.4 

241.6 

244.7 

249.6 

252.6 

257.4 

260.3 

265.1 

267.8 

272.6 

275.1 

279.9 

282.3 

45.5 

51.9 

58.1 

64.2 

70.3 

76.1 

81.7 

87.3 

92.8 

98.3 

103.7 

109.0 

114.0 

119.4 

124.7 

129.3 

134.3 

139.1 

143.9 

149.2 

153.7 

158.1 

163.2 

168.2 

172.3 

177.1 

181.9 

185.6 

190.2 

194.7 

199.2 

203.6 

207.9 

212.1 

216.3 

220.4 

224.4 

229.8 

233.7 

237.5 

241.3 

244.9 

250.1 

253.7 

257.2 

262.3 

265.7 

268.9 

274.0 

277.1 

282.2 

285.2 

290.2 

293.1 

298.1 

48.0 

54.7 

61.4 

67.8 

74.0 

80.3 

86.4 

92.2 

98.1 

103.8 

109.7 

115.0 

120.5 

125.9 

131.6 

136.6 

142.1 

147.4 

152.6 

157.7 

162.7 

167.6 

172.3 

177.7 

182.3 

186.7 

191.8 

196.9 

201.0 

206.0 

210.8 

215.6 

220.4 

223.9 

228.5 

233.0 

237.5 

241.8 

247.4 

251.7 

255.9 

260.0 

264.1 

268.1 

273.5 

277.4 

281.2 

284.9 

290.3 

293.9 

297.4 

302.7 

306.1 

311.4 

314.7 

50.9 

58.2 

65.1 

72.0 

78.7 

85.2 

91.8 

98.0 

104.4 

110.4 

116.5 

122.4 

128.4 

134.0 

139.7 

145.3 

151.3 

156.6 

162.3 

167.4 

172.9 

178.3 

183.5 

188.7 

193.8 

199.5 

204.3 

209.0 

214.5 

219.1 

224.4 

229.7 

233.9 

239.0 

244.1 

249.1 

254.1 

257.8 

262.6 

267.3 

272.0 

276.6 

281.1 

287.0 

291.4 

295.8 

300.1 

304.3 

308.5 

314.2 

318.3 

322.3 

326.2 

331.8 

335.6 

53.0 

60.5 

67.9 

74.9 

81.9 

88.8 

95.6 

102.1 

108.7 

115.1 

121.2 

127.5 

133.6 

139.9 

145.6 

151.6 

157.4 

163.1 

169.2 

174.7 

180.5 

185.7 

191.3 

196.8 

202.2 

207.6 

212.8 

218.6 

223.7 

228.6 

234.2 

239.0 

244.5 

249.0 

254.4 

259.7 

265.0 

269.1 

274.3 

279.3 

284.3 

289.3 

294.2 

299.0 

303.8 

308.5 

313.2 

317.7 

322.3 

326.7 

331.1 

337.0 

341.3 

345.5 

349.7


86 


Appendix E 

TABLE E13 – 

RAINFALL DURATION INTENSITY (min mm/hr) FOR MANGROVE CREEK DAM (t.I 0.4 ) 

MINUTES 

1 

YEAR 

2 

YEARS 

5 

YEARS 

10 

YEARS 

20 

YEARS 

50 

YEARS 

100 

YEARS 

6 

7 

8 

9 

10 

11 

12 

13 

14 

15 

16 

17 

18 

19 

20 

21 

22 

23 

24 

25 

26 

27 

28 

29 

30 

31 

32 

33 

34 

35 

36 

37 

38 

39 

40 

41 

42 

43 

44 

45 

46 

47 

48 

49 

50 

51 

52 

53 

54 

55 

56 

57 

58 

59 

60 

33.2 

37.9 

42.2 

46.6 

51.1 

55.0 

59.2 

63.1 

67.5 

71.1 

75.3 

78.6 

82.5 

86.3 

90.0 

93.7 

97.2 

100.6 

103.9 

107.1 

110.2 

114.5 

117.4 

120.2 

124.4 

127.0 

129.6 

133.6 

136.0 

140.0 

142.2 

146.1 

148.1 

152.0 

155.9 

157.7 

161.5 

163.1 

166.8 

170.6 

171.9 

175.6 

179.4 

180.4 

184.1 

187.7 

191.4 

192.1 

195.7 

199.3 

202.9 

203.2 

206.8 

210.3 

213.9 

36.8 

42.0 

46.9 

51.7 

56.5 

61.2 

65.6 

70.3 

74.4 

78.7 

82.8 

87.4 

91.3 

95.1 

99.4 

103.6 

106.9 

110.9 

114.8 

118.6 

122.3 

126.0 

129.5 

132.9 

137.5 

140.8 

144.1 

147.2 

151.6 

154.6 

157.4 

161.8 

164.5 

168.8 

171.4 

175.7 

178.0 

182.3 

184.5 

188.7 

190.7 

194.9 

196.7 

200.8 

204.9 

206.5 

210.6 

214.6 

216.0 

220.0 

224.0 

225.1 

229.1 

233.0 

233.9 

40.7 

46.4 

51.9 

57.2 

62.6 

67.7 

72.6 

77.6 

82.4 

87.0 

91.9 

96.6 

100.7 

105.1 

110.0 

114.2 

118.3 

122.9 

126.7 

131.1 

135.5 

138.9 

143.1 

147.2 

151.2 

155.1 

159.0 

162.7 

166.4 

171.3 

174.9 

178.3 

181.7 

186.5 

189.7 

192.9 

197.6 

200.6 

203.5 

208.1 

210.9 

215.5 

218.1 

222.6 

225.1 

229.6 

231.9 

236.4 

238.5 

242.9 

247.3 

249.3 

253.7 

255.4 

259.8 

42.8 

48.8 

54.7 

60.3 

65.8 

71.0 

76.3 

81.4 

86.5 

91.5 

96.4 

101.0 

105.9 

110.7 

115.4 

120.0 

124.4 

128.7 

133.5 

137.5 

142.2 

146.0 

150.5 

155.0 

159.3 

162.6 

166.8 

170.9 

174.9 

178.8 

182.7 

187.7 

191.5 

195.1 

198.7 

202.2 

207.1 

210.5 

213.7 

218.6 

221.7 

226.5 

229.5 

232.4 

237.2 

239.9 

244.6 

247.2 

251.9 

254.4 

259.0 

261.3 

265.9 

270.5 

272.6 

45.2 

51.7 

57.7 

63.8 

69.6 

75.2 

80.9 

86.1 

91.8 

96.9 

102.2 

107.3 

112.2 

117.0 

122.1 

127.0 

131.3 

136.0 

141.2 

145.7 

150.0 

155.0 

159.1 

164.0 

167.8 

172.5 

177.0 

181.6 

184.9 

189.3 

193.5 

197.7 

201.8 

205.8 

211.1 

215.0 

218.9 

222.6 

226.3 

231.5 

235.0 

238.5 

243.6 

246.9 

250.2 

255.2 

258.3 

261.4 

266.3 

269.2 

274.1 

276.9 

281.7 

284.4 

289.2 

48.4 

55.1 

61.7 

68.0 

74.2 

80.3 

86.1 

91.9 

97.8 

103.5 

109.0 

114.2 

119.7 

125.0 

130.1 

135.1 

140.5 

145.1 

150.2 

155.2 

160.0 

164.8 

169.4 

174.6 

179.0 

184.1 

188.3 

193.3 

197.2 

202.0 

206.7 

211.4 

216.0 

220.5 

224.9 

229.3 

233.7 

237.9 

242.1 

246.2 

250.2 

254.2 

258.0 

263.4 

267.2 

270.9 

276.2 

279.7 

283.2 

288.5 

291.8 

295.1 

300.3 

303.5 

308.6 

50.5 

57.6 

64.4 

71.2 

77.6 

84.0 

90.0 

96.2 

101.9 

108.0 

113.5 

119.1 

125.0 

130.2 

135.7 

141.1 

146.3 

151.9 

156.7 

162.1 

167.3 

172.4 

177.4 

182.2 

187.0 

191.6 

197.0 

201.4 

206.6 

210.8 

215.8 

220.8 

224.7 

229.5 

234.3 

239.0 

243.6 

248.1 

252.6 

257.1 

261.4 

265.7 

269.9 

274.1 

278.2 

283.7 

287.7 

291.6 

295.4 

300.9 

304.6 

308.2 

313.6 

317.2 

320.6


87 


Appendix E 

TABLE E14 - RAINFALL DURATION INTENSITY (min mm/hr) FOR PEATS RIDGE (t.I 0.4 ) 

MINUTES 

1 

YEAR 

2 

YEARS 

5 

YEARS 

10 

YEARS 

20 

YEARS 

50 

YEARS 

100 

YEARS 

6 

7 

8 

9 

10 

11 

12 

13 

14 

15 

16 

17 

18 

19 

20 

21 

22 

23 

24 

25 

26 

27 

28 

29 

30 

31 

32 

33 

34 

35 

36 

37 

38 

39 

40 

41 

42 

43 

44 

45 

46 

47 

48 

49 

50 

34.8 

39.8 

44.5 

49.2 

53.8 

58.1 

62.1 

66.4 

70.5 

74.5 

78.9 

82.6 

86.8 

90.1 

94.1 

98.0 

101.7 

105.4 

109.0 

112.5 

116.0 

119.3 

123.7 

126.8 

129.9 

134.2 

137.1 

139.9 

144.1 

146.8 

150.9 

153.4 

157.5 

159.8 

163.9 

166.0 

170.1 

172.0 

176.0 

180.0 

181.7 

185.6 

187.1 

191.0 

194.9 

38.5 

43.8 

49.0 

54.2 

59.1 

64.1 

68.9 

73.5 

77.9 

82.5 

87.0 

91.4 

95.6 

99.7 

104.2 

108.0 

112.4 

116.7 

120.1 

124.2 

128.2 

132.2 

136.0 

139.8 

143.5 

147.0 

151.8 

155.2 

158.6 

161.9 

166.5 

169.6 

172.6 

177.2 

180.1 

182.8 

187.3 

189.9 

194.3 

196.8 

201.2 

203.5 

207.8 

212.1 

214.2 

42.2 

48.1 

53.9 

59.4 

64.8 

70.2 

75.4 

80.7 

85.4 

90.7 

95.5 

100.0 

104.9 

109.6 

114.3 

118.7 

123.1 

128.0 

132.0 

136.8 

140.6 

145.1 

149.6 

153.1 

157.3 

161.6 

165.7 

169.7 

173.7 

177.6 

182.7 

186.4 

190.1 

193.7 

197.3 

202.2 

205.6 

208.9 

213.7 

216.9 

221.7 

224.7 

227.7 

232.4 

235.2 

44.2 

50.4 

56.4 

62.3 

67.9 

73.4 

78.9 

84.3 

89.4 

94.6 

99.7 

104.6 

109.8 

114.4 

119.4 

124.2 

128.8 

133.4 

138.5 

142.8 

147.0 

151.8 

155.8 

160.4 

165.1 

169.6 

174.1 

177.4 

181.7 

185.9 

190.0 

195.3 

199.3 

203.2 

207.1 

210.9 

214.6 

219.7 

223.3 

226.8 

231.8 

235.2 

238.4 

243.4 

246.6 

46.5 

53.0 

59.5 

65.7 

71.6 

77.6 

83.3 

88.8 

94.4 

99.7 

105.3 

110.6 

115.8 

120.8 

126.2 

130.9 

136.0 

141.0 

145.8 

150.6 

155.2 

160.4 

164.8 

169.0 

174.0 

178.9 

182.8 

187.5 

192.2 

196.8 

201.4 

205.8 

210.2 

214.6 

218.8 

223.0 

227.1 

231.2 

235.1 

239.0 

244.3 

248.1 

251.8 

257.0 

260.6 

49.4 

56.4 

63.1 

69.7 

76.1 

82.3 

88.3 

94.4 

100.2 

106.1 

111.8 

117.3 

123.0 

128.5 

133.9 

139.1 

144.2 

149.7 

155.0 

159.6 

164.7 

169.7 

175.5 

180.0 

184.7 

190.0 

194.4 

199.6 

203.8 

208.9 

213.8 

217.7 

222.5 

227.3 

232.0 

236.6 

241.2 

245.6 

250.1 

254.4 

258.7 

262.9 

268.5 

272.6 

276.6 

51.4 

58.6 

65.7 

72.5 

79.1 

85.6 

92.1 

98.2 

104.4 

110.4 

116.5 

122.4 

128.1 

133.6 

139.3 

144.9 

150.3 

155.6 

161.2 

166.2 

171.7 

177.0 

182.2 

187.3 

192.3 

197.2 

202.7 

207.4 

212.8 

217.3 

222.5 

226.8 

231.9 

237.0 

242.0 

245.8 

250.6 

255.4 

260.1 

264.8 

269.4 

273.9 

278.4 

282.8 

288.5


88 


Appendix E 

TABLE E15 - RAINFALL DURATION INTENSITY (min mm/hr) FOR NARARA (t.I 0.4 ) 

Minutes 

1 

Year 

2 

Years 

5 

Years 

10 

Years 

20 

Years 

50 

Years 

100 

Years 

6 

7 

8 

9 

10 

11 

12 

13 

14 

15 

16 

17 

18 

19 

20 

21 

22 

23 

24 

25 

26 

27 

28 

29 

30 

31 

32 

33 

34 

35 

36 

37 

38 

39 

40 

41 

42 

43 

44 

45 

46 

47 

48 

49 

50 

51 

52 

53 

54 

55 

56 

57 

58 

59 

60 

36.1 

41.2 

45.9 

50.9 

55.6 

60.2 

64.5 

69.0 

73.4 

77.7 

81.7 

85.7 

90.1 

93.7 

97.9 

102.0 

105.2 

109.1 

112.9 

116.6 

120.2 

123.8 

128.4 

131.8 

135.1 

138.2 

142.7 

145.8 

148.7 

153.1 

155.9 

158.5 

162.8 

165.3 

169.6 

171.9 

176.1 

178.3 

182.4 

186.6 

188.5 

192.6 

194.4 

198.4 

202.5 

204.0 

208.0 

212.0 

213.3 

217.2 

221.2 

222.2 

226.1 

230.0 

230.7 

39.8 

45.2 

50.7 

55.9 

61.0 

66.2 

70.9 

75.8 

80.8 

85.2 

90.0 

94.6 

99.0 

103.3 

107.5 

112.2 

116.1 

120.6 

125.1 

128.6 

132.8 

137.0 

141.1 

145.1 

149.0 

152.9 

156.6 

160.3 

163.9 

168.7 

172.1 

175.5 

178.8 

183.5 

186.6 

191.3 

194.2 

197.1 

201.7 

204.5 

209.0 

211.6 

216.1 

218.5 

223.0 

225.3 

229.7 

231.8 

236.2 

240.5 

242.4 

246.8 

248.5 

252.8 

257.1 

43.6 

49.7 

55.5 

61.3 

67.0 

72.4 

77.8 

83.3 

88.3 

93.5 

98.5 

103.7 

108.4 

113.4 

118.2 

123.0 

127.6 

132.1 

137.1 

141.3 

146.2 

150.2 

154.9 

158.6 

163.2 

167.6 

172.0 

176.3 

180.6 

184.7 

188.8 

192.8 

196.8 

200.6 

205.7 

209.5 

213.1 

216.7 

221.7 

225.2 

228.5 

233.2 

236.7 

239.8 

244.7 

247.7 

252.6 

255.4 

260.3 

263.0 

267.8 

270.4 

275.1 

277.6 

282.3 

45.2 

51.7 

57.9 

63.8 

69.9 

75.6 

81.2 

86.7 

92.4 

97.6 

102.9 

108.1 

113.1 

118.4 

123.6 

128.2 

133.1 

137.9 

143.2 

147.8 

152.3 

157.4 

161.6 

166.5 

170.5 

175.3 

180.0 

184.6 

189.2 

192.6 

196.9 

201.3 

205.5 

210.9 

215.0 

219.1 

223.1 

227.0 

230.8 

236.0 

239.7 

243.3 

246.9 

252.0 

255.5 

258.8 

263.9 

267.1 

272.1 

275.2 

280.2 

283.2 

288.1 

290.9 

295.9 

47.5 

54.2 

60.8 

67.1 

73.4 

79.4 

85.4 

91.4 

97.2 

102.8 

108.2 

113.8 

119.3 

124.5 

130.1 

135.1 

140.5 

145.7 

150.8 

155.8 

160.7 

165.5 

170.1 

175.4 

179.9 

185.0 

189.2 

194.2 

199.1 

204.0 

207.7 

212.4 

217.1 

221.6 

226.1 

230.6 

234.9 

239.2 

243.4 

247.6 

253.1 

257.1 

261.1 

265.0 

270.4 

274.2 

277.9 

281.5 

286.8 

290.3 

295.6 

299.0 

302.3 

307.5 

310.7 

50.4 

57.6 

64.6 

71.4 

77.8 

84.4 

90.7 

97.0 

103.1 

108.9 

114.8 

120.9 

126.5 

132.3 

138.0 

143.5 

148.8 

154.5 

159.6 

165.1 

170.4 

175.7 

180.8 

185.9 

190.8 

196.4 

201.1 

205.7 

211.1 

216.4 

220.6 

225.8 

230.9 

234.9 

239.8 

244.7 

249.5 

254.2 

258.9 

263.5 

268.1 

272.6 

277.0 

281.3 

285.6 

291.3 

295.5 

299.6 

303.7 

309.3 

313.2 

317.1 

320.9 

326.4 

330.1 

52.5 

59.9 

67.1 

74.2 

81.0 

87.6 

94.3 

100.7 

107.1 

113.4 

119.7 

125.5 

131.8 

137.5 

143.5 

149.0 

155.1 

160.7 

166.1 

171.9 

177.0 

182.6 

188.1 

193.5 

198.8 

203.9 

209.0 

214.7 

219.6 

224.3 

229.8 

235.3 

239.8 

245.1 

250.4 

254.5 

259.6 

264.7 

269.7 

274.6 

279.5 

284.3 

289.1 

293.8 

298.4 

302.9 

307.4 

311.9 

316.2 

322.1 

326.4 

330.6 

334.7 

338.8 

344.5


Appendix F 

MAXIMUM PERMISSIBLE GUTTER FLOW 

89 



KERB INLET CAPACITY 

Appendix G 

90 



Appendix H 

PRESSURE HEAD CHANGE COEFFICIENTS “ K “ DIAGRAMS 

91 



Appendix H 

92 



Appendix H 

93 



Appendix H 

94 



Appendix H 

95 



Appendix H 

96 



Appendix H 

97 



Appendix H 

98 



VELOCITY AND DISHARGE DIAGRAM 

Appendix I 

99 



Appendix J 

MINIMUM HGL OUTLET CONTROL LEVEL (AHD) 

Outlet 

Location 

Design Average Recurrence Interval 

1, 2, 5, 10 20 50 100 

All 

Discharges 

Design Discharge (m³/s) 


Appendix K 

PERCENTAGE IMPERVIOUS FOR VARIOUS ZONING AREAS 

% IMPERVIOUS 

ZONING Description 

1 (a) RURAL AGRICULTURAL 5% 

1 (b) RURAL GENERAL 5% 

1 (c) RURAL FORESTRY 5% 

1 (d) RURAL EXTRACTIVE MINERALS 5% 

1 (e) RURAL URBAN INVESTIGATION 5% 

2 (a) RESIDENTIAL “A” 70% 

2 (b) RESIDENTIAL “B” 80% 

2 (c) RESIDENTIAL “C” 80% 

2 (d) RESIDENTIAL “D” 80% 

3 (a) BUSINESS RETAIL 90% 

3 (b) BUSINESS COMMERCIAL 90% 

3 (c) BUSINESS CENTRAL 90% 

4 INDUSTRIAL GENERAL 80% 

5 (a) SPECIAL USES “A” 60% 

5 (b) SPECIAL USES “B” COMMUNITY PURPOSE 5% 

5 (c) SPECIAL USES “C” ROADS AND RAILWAY 50% 

6 (a) OPEN SPACE RECREATION 5% 

6 (b) OPEN SPACE ENVIRONMENTAL PROTECTION 5% 

6 (c) OPEN SPACE PRIVATE RECREATION 5% 

6 (d) OPEN SPACE PROPOSED 5% 

7 (a) SCENIC PROTECTION CONSERVATION 5% 

7 (b) SCENIC PROTECTION PLATEAU AREAS 5% 

7 (c) SCENIC PROTECTION SMALL RURAL HOLDINGS 5% 

7 (d) SCENIC PROTECTION TOURIST ACCOMMODATION 5% 

7 (e) COASTAL LAND ACQUISITION 5% 

8 

NATURAL PARKS, NATURE 

RESURVES AND STATE 

RECREATION AREAS 

5% 

9 RESTRICTED DEVOPMENT 5% 

101 



VOLUME AND DEPTH RELATIONSHIPS 

Appendix L 

Notes 

1. At velocities in excess of 2.0 m/s, the stability of foundations and poles can be 

affected by scour. Also, grass and earth surfaces begin to scour and can become 

rough and unstable. 

2. The velocity of floodwaters passing between buildings can produce a hazard, which 

may not be apparent if only the average velocity is considered. For instance, the 

velocity of floodwaters in a model test has risen from an average of 1 m/s to 3 m/s 

between houses. 

3. Vehicle instability is initially by buoyancy. 

4. At flood water depths in excess of 2.0 meters and even at low velocities, there can be 

damage to light-framed buildings from water pressure, flotation and debris impact. 

5. Derived from laboratory testing and flood conditions which caused damage. 

Taken from NSW Government Floodplain Management Manual (January 2001) 

102 



INTERALLOTMENT PIT SCHEDULE 

Appendix M 

A 

Pits In Driveways (Right Of Carriageway, Right Of Way And Access Handle) 

1. Pits located in driveways (Right of Carriageway, Right of Way and Access Handle) shall be cast in situ. 

2. Pits sizes, inlets and grate types shall be in accordance with the following table: 

Depth to invert D 

(mm)1 

Internal Pit Size 

(mm) 

Inlet type2 

Grate size and type 

D < 1800 900 x 670 Kerb Inlet 900 x 450 Heavy duty hinged 

grate 

D ≥ 1800 900 x 900 Kerb Inlet 900 x 450 Heavy duty hinged 

grate 

B 

Inter-Allotment Drainage (For Pits Not Situated in Driveways) 

epth to Invert, D 

(mm)3 

Internal Pit Size 

(mm) 

Inlet Type4 

Grate size and type 

D < 450 450 x 450 Grated Surface Inlet 450 x 450 hinged grate 

450 ≤ D < 900 600 x 600 Grated Surface Inlet 600 x 600 hinged grate 

900 ≤ D


STANDARDS AND GUIDELINES 

Appendix N 

DOCUMENT AUTHOR YEAR 

ACID SULPHATE SOIL, Policy and Procedures RTA 1995 

AIR QUALITY ASSESSMENT OF MAJOR RTA 

PROJECTS, Guidelines for pre-construction 

RTA 

1994 

AUSTRALIAN RAINFALL AND RUNOFF 

THE INSTITUTION OF 

ENGINEERS, AUSTRALIA 2000 

BEHAVIOURAL ISSUES IN ROAD SAFETY, A 

guide to the major problems and solutions 

RTA 

1995 

CONCRETE PIPE SELECTION AND 

INSTALLATION 

CONCRETE PIPE 

ASSOCIATION OF 

AUSTRALIA 1990 

DESIGN VEHICLES AND TURNING 

TEMPLATES 

NAASRA 

1986 

DRAINAGE OF WIDE FLAT PAVEMENTS NAASRA 1974 

DRIVEWAY ENTRANCES ON MAJOR ROADS 

IN URBAN AREAS, Guides for the design of 

NAASRA 

1978 

ECONOMIC ANALYSIS MANUAL RTA 1990 

ENVIRONMENT MANUAL 

Volume 1: Environmental Policy 

Volume 2: Interim Traffic Noise Policy 

Volume 3: Environmental Impact 

Assessment, Guidelines 

RTA 

RTA 

RTA 

1993 

1992 

1993 

ESTIMATING, Project RTA 1990 

ESTIMATING, Manual RTA 1991 

FLOODPLAIN MANAGEMENT MANUAL NSW Government 2001 

GEOMETRIC DESIGN OF FREEWAYS AND 

EXPRESSWAYS, Guide Policy for 

GEOMETRIC DESIGN OF MAJOR URBAN 

ROADS, Guide Policy for 

GEOMETRIC DESIGN OF RURAL ROADS, 

Guide to 

NAASRA 

NAASRA 

AUSTROADS 

1976 

1976 

1993 

GRADE SEPARATED INTERCHANGES NAASRA 1984 

MODEL ANALYSIS TO DETERMINE DMR 1979 

104 




HYDRAULIC CAPACITIES OF KERB INLETS 

AND GULLY PIT GRATINGS 

NOISE BARRIERS AND CATALOGUE OF 

SELECTION POSSIBILITIES 

RTA 

1991 

PLANNING AND DESIGN GUIDE RTA 1990 

POLLUTION CONTROL MANUAL FOR URBAN 

STORMWATER 

STATE POLLUTION 

CONTROL COMMISSION 1989 

ROAD DESIGN, Guide 

‣ Section 1: Basic Design Criteria 

‣ Section 2: Road Geometry 

‣ Section 3: Cross Section 

‣ Section 4: Intersections at Grade (Draft) 

‣ Section 5: Design of Earth Structures (Draft) 

‣ Section 6: Safety Barriers for Roads and 

Bridges (Draft) 

‣ Section 7: Drainage (Draft) 

‣ Section 8: Erosion and Sedimentation 

‣ Section 9: Miscellaneous 

‣ Glossary of Terms 

RTA 

1991 

1988 

1988 

1991 

1989 

1993 

1990 

1993 

1988 

1989 

ROAD ENVIRONMENT SAFETY GUIDELINES RTA 1992 

ROAD MEDIANS NAASRA 1984 

ROAD SAFETY AUDITS AUSTROADS 1994 

ROAD SAFETY AUDITS RTA 1995 

ROAD SURFACE DRAINAGE, Guide to the 

design of 

ROAD TRAFFIC ACCIDENTS IN NSW 

NAASRA 

RTA 

1986 

ROUNDABOUT DESIGN, Guide to RTA 1984 

SPECIFICATION SI/TCS/7 

‣ Installation and Reconstruction of Traffic 

Light Signals 

‣ Associated Drawings for 

STORM DRAINAGE DESIGN IN SMALL URBAN 

CATCHMENTS: SPECIAL REPORT _ 34 

STORMWATER QUALITY TREATMENT 

GUIDELINES (Draft) 

SUBSURFACE DRAINAGE OF ROAD 

STRUCTURES: REPORT _ 35 

RTA 

ARRB 

RTA 

ARRB 

1991 

1986 

1994 

19987 

105 




TRAFFIC ENGINEERING PRACTICE, Guide to 

‣ Part 1: Traffic Flow 

‣ Part 2: Roadway Capacity 

‣ Part 3: Traffic Studies 

‣ Part 4: road Crashes 

‣ Part 5: Intersections At Grade 

‣ Part 6: Roundabouts 

‣ Part 7: Traffic Signals 

‣ Part 8: Traffic Control Devices 

‣ Part 9: Arterial Road Traffic Management 

‣ Part 10: Local Area Traffic Management 

‣ Part 11: Parking 

‣ Part 12: Roadway Lighting 

‣ Part 13: Pedestrians 

‣ Part 14: Bicycles 

‣ Part 15: Motorcycle Safety 

Manual of Uniform Traffic Control Devices 

Part 2: Traffic control devices for general use 

Part 9 Bicycle facilities 

Part 10 Pedestrian control and protection 

Part 11 Parking control 

Part 13 Local area traffic management 

AUSTROADS 

AUSTROADS 

AUSTROADS 

AUSTROADS 

AUSTROADS 

AUSTROADS 

AUSTROADS 

AUSTROADS 

AUSTROADS 

AUSTROADS 

AUSTROADS 

AUSTROADS 

AUSTROADS 

AUSTROADS 

AUSTROADS 

AUSTRALIAN STANDARD 

AS 1742 .2 

AS1742 .9 

AS1742 .10 

AS1742.11 

AS1742.13 

1988 

1988 

1988 

1988 

1988 

1988 

1993 

1993 

1988 

1988 

1988 

1994 

1988 

1999 

1999 

1994 

1994 

1994 

1994 

1994 

1994 

Road signs – Specification AS 1743 1992 

Parking facilities 

Part 1 Off – street car parking 

Part 2 Commercial vehicle facilities 

Part 3 Bicycle parking facilities 

Part 5 On - street parking 

AS 2890.1 

AS 2890.2 

AS 2890.3 

AS 2890.5 

1989 

1989 

1993 

1993 

TRAFFIC SIGNAL DESIGN STANDARDS AS 1743 1994 

TRAFFIC GENERATING DEVELOPMENTS RTA 1993 

TRAFFIC SIGNAL DESIGN STANDARDS RTA 1994 

TRAFFIC SIGNAL PRACTICE - DESIGN RTA 1992 

TRAFFIC SIGNALS: Capacity and Timing 

Analysis 

ARRB 

1983 

WIRING RULES AS3000 SSA 1994 

106 



Appendix O 

STORMWATER DRAINAGE CALCULATION FORM DETAILS 

The following details refer to the column numbers on the Stormwater Drainage Calculation Form 

in Appendix B 

1 CATCHMENT REFERENCE - COLUMN 1 

This refers to the sub-catchment area reference number. Each sub-catchment shall have 

a separate reference number that must be consistently used on the catchment plan, main 

plan view and the stormwater drainage calculation form 

2 LENGTH OF SECTION - COLUMN 2 

This refers to the length of the pipeline or drain from the sub-catchment inlet under 

consideration to the next downstream inlet. This length may be obtained from the 

longitudinal section or plan. 

3 OVERLAND FLOW - COLUMNS 3 TO 6 

For small to medium sized rural or natural bushland catchments the "time of 

concentration" shall be determined using Equation 5.4 in AR & R, 1987, 

ie t c = 0.76 A 0.38 

where 

A = catchment area in km² 

t c = time in hours 

For areas expressed in hectares and time in minutes this formula becomes:- 

t c = 7.924 A 0.38 

For urban catchments the "kinematic wave" equation (Equation 14.2 in AR & R, 1987) 

shall be used to determine the appropriate "time of concentration", 

ie t c = 6.94 (L x n*) 0.6 / I 0.4 x S 0.3 

where t c 

= time of concentration in minutes 

L = overland flow path length (m) 

n* = surface roughness coefficient [refer Table 14.4 AR & R, 

1987] 

(NOT equivalent to Manning 'n' values) 

I = rainfall intensity (mm/hr) 

S = catchment slope (m/m) 

To enable direct determination of t c by this formula Tables E11 to E15 containing t.I 0.4 

values. 

The kinematic wave equation only applies to planes of flow, which are homogeneous in 

slope and surface roughness. For heterogeneous sub-catchments segmental calculation 

107 



of overland flow time using Equation 14.3 - AR & R, 1987 should be undertaken. 

Where the critical sub-catchment flow enters a channel or diversion drain prior to arriving 

at the inlet under consideration the flow velocity along the drain can be determined using 

Manning Formula (Equation 14.4 - AR & R, 1987) and the additional time of overland 

flow to the inlet determined by dividing the drain length by the flow velocity. 

Partial Area Effects as discussed in Section 14.5.5(ii) of AR & R, 1987 should be 

considered before adopting the value of t c derived. 

The length of overland flow and grade is obtained from the contoured catchment area 

plan, the length being measured normal to the contours from the head of the catchment 

to the point of entry to the gutter, pit or headwall. 

The effect of property boundary fencing on the likely overland flow path should be 

considered. 

The type of surface ('n' value) to be used should cater for likely future land use type, 

which may not necessarily be the existing. For instance urban zoned land at present 

used for rural purposes will most likely in the future become residential and the 

coefficient n = 0.17 "Average Grassed Surface" should be used to reflect average urban 

development. 

Where rezoning is likely the future flow patterns will have to be estimated, eg an overland 

flow at the top of the catchment of say 100 metres and thence by gutter or pipe. 

Council's Development/Environment Directorate, Urban Planning Section or the 

Department of Environment should be consulted to determine the likely long-term land 

use characteristics. 

4 TIME OF FLOW IN GUTTERS - COLUMNS 7 TO 9 

Use Figure D1 in Appendix D. 

This nomograph is used where the catchment area is wholly road or where the longest 

overland flow path meets the gutter above a pit. 

5 MAXIMUM FLOW TIME - COLUMN 10 

This is the sum of the values shown in Columns 6 and 9. 

The minimum time of concentration is six (6) minutes and this value is to be used where 

the calculated time is less than six (6) minutes. 

6 AVERAGE RECURRENCE INTERVAL - COLUMN 11 

The appropriate design average recurrence interval (ARI) should be obtained from the 

following list. 

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Drainage Situation 

Design Flood 

Average 

Recurrence Interval 

Excess Flow Passage 

1 Residential streets and catch 

drains with overflow or 

bypass along the street 


drains at low points with 

overflow along public 

reserves and pathways 


drains at low points with 

drainage lines traversing 

building allotments or other 

locations where surface flow 

may cause property damage 

4 Major system traversing 

developed areas 

(residential, commercial or 

industrial) 

(Major systems are defined 

as those having catchment 

areas in excess of 15 ha or 

having 100 year ARI runoffs 

in excess of 3 m³/second 

whichever is the lesser.) 

5 Industrial and neighbourhood 

business areas 

10 Years 

10 years 

20 years generally, 

100 years if no 

escape route 

100 year flood to be 

confined to carriageway, 

pathway or reserve 

100 year flood to be 

confined to carriageway, 

pathway or reserve 

The 100 year flood edge of 

stream is to be shown on 

the plans so that appropriate 

easement width and 

treatment of escape route 

can be determined 

100 years The 100 year flood edge of 






20 years generally, 

100 years if no 

escape route 

The 100 year flood edge of 






6 Larger business areas 100 years The 100 year flood edge of 






NOTE 1 In any specific case where damage to property or unusual inconvenience is 

likely to result from surcharging of the drainage system, a longer average 

recurrence interval may be required to be used than those given above. 

109 



2 Appropriate freeboards are to be provided and incorporated into the excess 

flow passage. Confirm freeboard with Project Manager at start of design. 

7 RAINFALL INTENSITY 'I' - COLUMN 12 

Obtained from Table E1 to E5 "Rainfall Intensity/Frequency/Duration Data" shown in 

Appendix E. From the time in minutes (Column 10) proceed horizontally to the required 

average recurrence interval (Column 11) and read the intensity. Intensities are given in 

mm/hour. 

The five sheets comprising Table E1 to E5 correspond to the five zones shown on 

Figure E1. The zone boundaries generally reflect major catchment watersheds however 

where the catchment under consideration overlaps a zone boundary the higher rainfall 

intensity value should be used. 

For durations and average recurrence intervals in excess of those shown in Table E1 the 

rainfall intensity should be determined by the method set out in AR & R, 1987. 

8 SUB-CATCHMENT AREA - COLUMN 13 

The total area of the sub-catchment in hectares obtained from the catchment area plan. 

9 % IMPERVIOUS AREA - COLUMN 14 

The impervious area of the sub-catchment in hectares obtained from the catchment plan 

expressed as a percentage of the total sub-catchment area shown in Column 13. 

10 RUNOFF COEFFICIENT C 10 - COLUMN 15 

For urban catchments this value is obtained from Figure E2 in Appendix E using the 

percentage impervious area shown in Column 14. 

For rural or natural bushland catchments throughout the City of Gosford a value of C 10 = 

0.60 should be used. 

11 SUB-AREA C 10 A - COLUMN 16 

This is the product of the numbers in Columns 13 and 15. 

12 FREQUENCY FACTOR - COLUMN 17 

110 



This value is obtained from the following table corresponding to the average recurrence 

interval shown in Column 11 and catchment type under consideration. 

Average Recurrence Interval (years) 

Catchment Type 1 2 5 10 20 50 100 

Urban (Fy) 0.80 0.85 0.95 1.00 1.05 1.15 1.20 

Rural/Natural (FFy) 0.62 0.74 0.88 1.00 1.12 1.26 1.39 

13 RUNOFF COEFFICIENT C Y - COLUMN 18 

This value is the product of the numbers in Columns 15 and 17. 

14 SUB AREA EIA - COLUMN 19 

This amount is the product of values in Columns 13 and 18. 

15 FLOW - SUB AREA - COLUMN 20 

The product of the figures in Columns 12 and 19 and the constant 'F' = 0.00278 to give the 

sub area runoff in cumecs (m³/s). 

16 FLOW - BYPASS - COLUMN 21 

The quantity of flow from an upstream catchment area which is added by reason of bypass 

from a pit above. Transfer from upstream pit value in Column 24. 

NOTE that this bypass value is not necessarily that from the pit immediately above in the 

calculation sheet. 

17 FLOW - TOTAL - COLUMN 22 

This value is the sum of figures in Columns 20 and 21. 

The maximum permissible flow along a kerbed and guttered road shall be determined from 

Figure F1 in Appendix F. 

If the calculated flow in Column 22 is significantly greater (more than 10%) than the 

maximum permissible gutter flow obtained from Figure F1, then either:- 

a 

b 

the upstream bypass flow should be reduced by providing improved flow collection at 

the upstream pit; and/or 

the pit location should be changed to provide a reduced pit sub-catchment area and 

hence reduce the runoff flow. 

111 



NOTE:- where a vehicular travelling lane is adjacent to the kerb or where there is a 

low-level footpath, then the maximum tolerable depth of gutter flow is considered to be 

75 mm. 

ALSO NOTE that for kerb side parking lanes or cycleways with adjacent high level 

footpaths the maximum tolerable depth of gutter flow is considered to be 125 mm. 

Where a roadway is intended to act as the "major" link (secondary flow path or floodway) 

as part of a major/minor drainage system then the maximum permissible flow along the 

street should have a product of flow velocity and depth equal to 0.4 m²/s for pedestrian 

safety with an absolute maximum product of 0.6 m²/s for vehicle safety. 

18 INLET TYPE - COLUMN 23 

For kerb and gutter at grades up to 10% (excluding sag low points) the capacity of various 

standard inlet types may be obtained from Figure G1 shown in Appendix G. For kerb 

grades between 10% and 15% the inlet capacity is considered to be half of that obtained 

from Figure G1 and for grades above 15% a value of one quarter of that obtained from 

Figure G1 should be used. 

Kerb inlets (KI) should be used in all locations except where pits are located at access 

crossings or where design gutter flows are less than 0.03 cumecs. 

A KI should be 1.8 metres generally and 2.4 metres maximum length. Where one inlet is 

inadequate consideration should be given to construction of an additional pit approximately 

5.0 metres upstream to collect the flow or to allow bypass to the next downstream pit. 

At a letterbox type inlet the maximum permissible table drain flow is 0.20 cumecs. 

Need for curved KI's should be avoided wherever possible. 

The inlet capacity of convex curved KI's is considered to be half that of a similar straight 

KI. 

The inlet capacity of a concave curved KI is considered to be equal to that of a straight KI. 

At sag pits some judgement must be used to ensure that the width of gutter flow is not too 

great. 

Pits either side of a sag pit should be designed for 100% collection of any surcharge or 

bypass flows resulting from the design rainfall intensity for the sag pit applied over the total 

upstream catchment area. Such pits should be close enough to the sag point to keep 

collection by the sag pit to a minimum. 

A sag pit with a 1.8 metre KI (the minimum permitted) is estimated to have a capacity of 

0.10 cumecs but, because of the restriction on width of flow and the potential for blockage 

it is seldom that such a quantity can be permitted to reach the pit. 

112 



19 AMOUNT BYPASSING - COLUMN 24 

This is the difference between the total gutter flow (Column 22) and the inlet capacity (from 

Figure G1). 

The amount of bypass calculated should not exceed 25% of the total inlet flow 

(Column 22). 

20 TIME IN CULVERT - COLUMN 25 

This value relates to the section of pipeline or open channel immediately upstream of the 

pit under consideration. Where a pit has two or more inlet pipelines then the critical section 

shall be defined as that section of pipeline having the longest "critical time of 

concentration" - see Column 26. 

Where a pit has no inlet pipeline (grate inflow only) this column should be left blank. 

The time in culvert is determined by dividing the upstream length of the critical section 

(Column 2) by the upstream drain flow velocity (Column 32) and converted to minutes 

21 CRITICAL TIME OF CONCENTRATION - COLUMN 26 

This is the same as the maximum flow time (Column 10) for the inlet at the head of a 

pipeline. 

For pits lower down the pipeline network it is the greater time of either:- 

a 

b 

the maximum flow time (Column 10) for the pit under consideration, or 

the longest upstream critical time of concentration (Column 26 upstream) plus the 

time in drain (Column 25) from this upstream pit. 

Care should be exercised when determining the critical time of concentration to ensure 

that a small elongated section of the total catchment area does not govern the critical time 

of concentration and hence significantly distort the design discharge for the majority of the 

catchment. This characteristic - Partial Area Effects - is discussed in Section 14.5.5 in 

AR & R, 1987. 

22 RAINFALL INTENSITY - COLUMN 27 

This is the intensity for the critical time of concentration and is taken from Table E1 in 

Appendix E using the average recurrence interval shown in Column 11 and the appropriate 

catchment zone. 

23 TOTAL C 10 A - COLUMN 28 

This is the total of all upstream values of Column 28 which contribute to the section of 

drain under consideration plus the value shown in Column 16. 

24 TOTAL EIA - COLUMN 29 

113 



This is the product of the values in Column 17 and 28. 

25 DISCHARGE - COLUMN 30 

The product of Columns 27 and 29 and the constant F = 0.00278 to give the discharge in 

cumecs. 

26 SIZE OF CULVERT - COLUMN 31 

The minimum diameter pipe should generally be 375 mm with 300 mm diameter 

permissible only in exceptional circumstances. 

The potential for debris blockage of small culverts should also be considered. For short 

drains in rural or bushland areas or pipelines intended as a low flow system a general 

minimum size of 750 mm diameter is recommended. Provision of suitable trash racks on 

the inlet should also be considered. 

The drainage culvert (pipe or box culvert) size should be determined using the Manning 

Formula with n = 0.012 for precast concrete, 

Q = A.R. 0.67 S 0.5 

n 

where 

A = cross sectional area of culvert (m²) 

R = hydraulic radius of culvert 

S = slope of culvert (decimal) 

Q = culvert capacity (m³/s) 

n = Manning roughness coefficient 

Figure I1 may be used for the design of pipelines, as precast concrete pipe culverts are 

preferred for ease of construction. Box culverts should be avoided wherever possible, as 

their construction cost is generally greater than that of multi-cell pipelines with similar 

capacity. 

Culverts made from material other than reinforced concrete (such as aluminium, fibre 

reinforced cement, glass fibre reinforced plastic, plastic or PVC) may be acceptable for 

some applications however their use and hydraulic properties must be approved by the 

Project Manager prior to their inclusion in the detailed design. 

Estimation of the Manning roughness parameter for open channels should be in 

accordance with Section 4.8 of AR & R, 1987. Conservative estimates should be used to 

reflect a "worst case" or poor channel condition. 

27 VELOCITY IN CULVERT - COLUMN 32 

This is determined for the culvert entrance only and is not necessarily the actual flow 

velocity along the drain. 

Assuming the culvert entrance is submerged, the entrance velocity is equal to the pit 

discharge (Column 30) divided by the cross sectional area of the outlet culvert(s) selected, 

114 



ie 

V = Q/A 

If the culvert is not submerged then open channel flow conditions prevail and the velocity 

may be determined using the actual waterway area of the flow at the culvert entrance, 

ie 

V = Q/A actual 

A general maximum design flow velocity in concrete culverts of 5.0 m/s is recommended. 

A minimum self cleaning velocity of 0.6 m/s under design conditions is required. 

At the outlet of culverts or lined channels with design velocities greater than 2.0 m/s 

provision of energy dissipation structures or scour protection measures should be 

included. 

For natural creeks or large grass-lined channels a maximum design flow velocity of 2.0 m/s 

is recommended with a velocity of 3.0 m/s permitted only in exceptional circumstances 

(refer to Table 14.18 in AR & R, 1987). 

28 INLET/BEND NUMBER - COLUMN 33 

This number is the numeric inlet pit reference number corresponding with that number 

shown on the plan and longitudinal section. The numbering system is sequential 

numbering of each pit upstream along that line, ie Pit 1 is downstream from Pit 2, etc. 

When a junction of pipelines occurs, a new "Line" will be considered to commence. For 

example, with a junction at Pit 3, Line 1: 

Line 1 = 1 - 2 - 3 - 4, and 

Line 2 = 3 - 5 - 6 - 7, etc. 

A separate line should be included in the calculation sheet for each inspection pit and each 

mitre bend or "lobster back" bend in the pipeline system to provide details for the HGL 

design. Each such pit or bend should be given a sequential number as if the structure was 

an inlet pit. 

115 



29 'K' - HEAD CHANGE COEFFICIENT - COLUMN 34 

The 'K' value is the Pressure Head Change Coefficient for a headwall, pit or pipe bend. It 

shall normally be derived from the appropriate figures given in Appendix H. However, if an 

unusual pit configuration arises then an acceptable 'K' value shall be determined following 

discussions with the Project Manager. 

Figures H1 to H11 are only DIRECTLY applicable to pipelines constructed "in line". That 

is, with both the inlet and outlet pipelines at a pit aligned vertically between matching 

inverts and matching obverts and with similar lateral alignment. The pipe centre lines must 

also intersect at or near the downstream face of the pit. 

When pipelines at a pit are not "in line" (ie "offset"), the value of 'K' obtained from 

Figure H12 shall be added to the value obtained from Figures H6 to H11. 

At the junction of two pipelines where a significant offset through the pit occurs (ie h/Du 

Ratio 1.6 - see Figure H12) then a value of K = 3.0 shall be used, ie similar to grate inflow 

only. 

At the junction of three pipelines the following guidelines for the use of Figure H12 shall be 

adopted. 

Where only one inlet pipeline is offset from the outlet pipeline then:- 

a 

b 

if the upstream pipeline (DU) is offset, use h/DU for the pipeline offset ratio in 

Figure H12, or 

if the lateral pipeline (DL) is offset, use h/DL for the pipeline offset ratio in 

Figure H12. 

Where both inlet pipelines are offset from the outlet pipeline then:- 

a 

b 

if (Q U x h U ) (Q L x h L ) - use h U /D U for the pipeline offset ratio with Q U = Q DROP 

in Figure H12, or 

if (Q U x h U ) < (Q L x h L ) - use h L /D L for the pipeline offset ratio with Q L = Q DROP in 

Figure H12. 

If the total value of 'K' determined from Figures H5 and H6 plus the value of 'K' obtained in 

accordance with Clause 4.31.05.01 or 4.31.05.02 above is greater than 3.0, then a value 

of K = 3.0 should be adopted for the pit. 

30 HEAD CHANGE - COLUMN 35 

This is the change in the hydraulic grade line (HGL) elevation due to the effect of either a 

pit's inlet and outlet geometry, the presence of a mitre bend in the pipeline or a sudden 

expansion or contraction of the pipeline size. 

The HGL is considered to be equal to the free water surface level. 

116 



The pressure head change (H p ) is determined as follows:- 

H p = KV² 

19.62 

where 

K = Pressure Head Change Coefficient shown in Column 34; and 

V = Outlet velocity in the culvert shown in Column 32 

For pipelines, creeks or channels with outlets into tidal waters or coastal lakes or lagoons 

the minimum HGL outlet control level for design should be obtained from the following 

table. 

MINIMUM HGL OUTLET CONTROL LEVEL (AHD) 

Design Average Recurrence Interval 

1, 2, 5, 10 20 50 100 

Outlet 

Location 

Design Discharge (m³/s) 

All 

Discharges 3 3 3 

Brisbane Water and 

tributaries 

(upstream of The 

Rip) 0.35 0.35 0.70 0.70 1.00 1.00 1.50 

Brisbane Water 

(between Half Tide 

Rocks and The Rip) 0.45 0.45 0.80 0.80 1.20 1.20 1.60 

Pacific Ocean/ 

Broken Bay 0.50 0.50 0.80 0.80 1.20 1.20 1.60 

Terrigal Lagoon 1.40 1.40 1.80 1.80 2.20 2.20 2.60 

Wamberal Lagoon 2.40 2.40 2.60 2.60 2.80 2.80 3.00 

Cochrone Lagoon 2.60 2.60 2.90 2.90 3.40 3.40 3.70 

Avoca Lake 2.15 2.15 2.50 2.50 2.80 2.80 3.10 

Pearl Beach Lagoon 3.20 3.20 3.40 3.40 3.60 3.60 3.70 

Hawkesbury River 

and tributaries 0.50 0.50 0.90 0.90 1.30 

Consult Project 

Manager 

Other large water 

bodies 

Consult Project Manager 

No additional allowance should be made for any possible "Greenhouse Effect" on tidal waters. 

117 



31 MINIMUM FRICTION GRADE (mfg) - COLUMN 36 

This grade is the minimum necessary to overcome the frictional effect of the water flow 

against the culvert surface in order to maintain a constant flow velocity. 

It can be obtained from Figure I1 or determined using the Manning Formula, 

ie 

mfg = Q.n 2 

( ) A.R 2/3 

Comments 

where Q = Discharge (Column 30) 

n = Manning roughness coefficient 

A = Cross sectional area of culvert 

R = Hydraulic radius of culvert 

Brief comments on the drainage design for example if the pit is likely to surcharge and a bolt 

down pit is required. 

118

gcc design specification - Gosford City Council - NSW Government

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