Appendix P Drainage, Flooding, Stormwater Management Part 5

Flooding, Drainage and Stormwater Management
Sanctuary Villages
Table 4-1:
XP-RAFTS
Node
100 year flows adopted in hydraulic model
Creek
HEC-RAS
Crosssection
100 Year Flow Rate
(m 3 /s)
QUO.5 Quorrobolong 2695.4 286.3
QUO.6 Quorrobolong 1905.17 299.9
CON.10 Congewai 6231.75 370.0
CON.11 Congewai 4363.81 700.0
CON.14A Congewai 1643.19 746.8
CON.15 Congewai 304.12 761
UNK.4 Unnamed 582.97 14.0
UNK.7 Unnamed 1864.4 60.1
UNK.9 Unnamed 1864.32 3.1
4.1.4 Energy loss coefficients
Several types of loss coefficients are utilised by the program to evaluate head losses. These
are:
Manning’s ‘n’ values for friction losses in the defined creek line and overbank regions.
The Manning’s ‘n’ for the defined creek line and overbank regions varied depending on
vegetation type (U.S. Army Corps of Engineers, 1998); and
Contraction and expansion coefficients to evaluate creek transition losses. For gradual
transitions, the contraction coefficient was assumed to be 0.1 with the expansion
coefficient being 0.3 (U.S. Army Corps of Engineers, 1998).
4.1.5 Cross section geometry
Boundary geometry for the analysis of flow in natural watercourses is specified in terms of
ground surface profiles (cross sections) and the measured distance between these profiles
(reach lengths).
Creek cross sections were determined from aerial survey of the site. The locations of all
cross sections utilised in this analysis are shown in Figure 6.
4.1.6 Reach length
The measured distances between cross sections are referred to as reach lengths and are
typically measured along the centreline of the defined creek line. Distances between
overbank regions are measured between upstream and downstream cross section overbank
regions.
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