North Peoria Area Drainage Master Plan - Flood Control District of ...
North Peoria Area Drainage Master Plan - Flood Control District of ... North Peoria Area Drainage Master Plan - Flood Control District of ...
• Basin Outlet (Culvert). The basin outletstructure should be sized to convey the100-year existing (pre-development) conditionpeak discharge without disruptingthe sediment transport capabilities of thechannel for the 2-year and 10-year events.If the basin is to be located at a roadwaycrossing (collector and arterial roadways),then at a minimum, the 100-year future(post-development) condition water surfaceelevation must not be more than 0.5feet above the minimum roadway elevationand flow from the 50-year future conditionevent must not overflow theroadway. Other design guidelines for culvertssuch as sediment deposition, scourholes and long-term degradation mustalso be considered and these guidelinesare presented in subsequent sections.• Basin Volume. The storage volume that isrequired to satisfy the discharge requirementsstated above must consider thepotential loss of storage due to sedimentdeposition. Sediment deposition couldpotentially impact the hydraulic operationof the basin ultimately effecting the maximumwater surface elevation. The storagevolume must also be checked in conjunctionwith the embankment height inregard to the jurisdictional classification.Structures that meet jurisdictional damclassification requirements must bedesigned in conformance with ADWRrequirements, and the design must beapproved by ADWR. Jurisdictional classificationis discussed previously in theearthen dam guideline section.• Drain Time. The basin must be drainedwithin 36 hours after the end of the designstorm.• Downstream Impacts. Hydrologic modelingshall be done to determine if thedetainment of runoff or the increased runoffdue to development worsens existingconditions. Modeling of multiple stormfrequencies (at a minimum 2-, 10-, and100-year events) may be required.33In-stream, in-line detention basins should notbe considered for areas that are characterizedby wide flood plains, significant conveyancein the overbank area or multiple channels.The opportunity to enhance stormwater qualityis minimal for an in-stream, in-line detentionbasin and is not recommended forwatersheds in which the land use is high densityor because of the land use, the percent ofimpervious cover is greatly increased unless,stormwater quality concerns have beenaddressed within the watershed draining tothe site.In-stream, Off-line Retention BasinIn-stream, off-line retention basins are stormwaterstorage basins that could be employed,with authorization from the reviewing agency,instead of the standard retention practice. Instream,off-line retention basins function toreduce post development peak discharge andvolume to pre-development values. Majorelements of the facility are channelization andgrade control structures to control the hydraulicsof the flow; inlet works (typically a weir)to direct flow to the basin, low level outlet todrain the basin and a basin of sufficient volumeto reduce peak discharges. The followingguidelines/consideration should beaddressed in the design of such a facility:• Modeling Software. The current recommendedmodeling software is the Corps ofEngineers HEC-RAS v3.0 using theunsteady flow module.• Flow Regime. The flow regime in the watercourseat the lateral weir structure shouldbe subcritical. This may require the channelizationand/or construction of gradecontrol structures. Design guidelines forchannelization must also be consideredand those guidelines are presented in followingsections.• Grade Control Structures. Grade controlstructures or drop structures may berequired to control flow in the naturalchannel to subcritical flow conditions.
NORTH PEORIAAREA DRAINAGE MASTER PLANThe armored length of the structureshould be sufficient to eliminate developmentof a scour hole downstream of thestructure.• Lateral Weir. The lateral weir must besized such that the remaining peak flowand total runoff volume is equivalent toexisting conditions for the design storm.The weir crest elevation must be sufficientlyhigh enough to eliminate potentialbackwater conditions caused by the pondedwater in the basin that would reducethe efficiency of the weir. The potential forscour at the downstream toe of the weirmust be addressed. Sediment depositionwithin the channel at the toe of the weircould significantly alter the hydraulicoperation of the weir and thus the basin.Sediment deposition at the toe of the weirmust be regularly removed.• Drain Time. The basin must be drainedwithin 36 hours after the end of the designstorm. To accomplish this, it may be necessaryto provide a small bleed-off culvert.For this situation, the minimum practicalculvert size should be used. Designguidelines for culverts must also be consideredand those guidelines are presentedin subsequent sections.• Basin Volume. The storage volume that isrequired must consider the potential lossof storage due to sediment deposition.Sediment deposition could potentiallyimpact the hydraulic operation of thebasin ultimately effecting the maximumwater surface elevation. The storage volumemust also be checked in conjunctionwith the embankment height in regard tothe jurisdictional classification. Structuresthat meet jurisdictional dam classificationrequirements must be designed in conformancewith ADWR requirements, andthe design must be approved by ADWR.Jurisdictional classification is discussedpreviously in the earthen dam guidelinesection.• Downstream Impacts. Hydrologic modelingshall be done to determine if thedetainment of runoff or the increased runoffdue to development worsens existingconditions. Modeling of multiple stormfrequencies may be required.• An in-stream, off-line retention basin reducespeak discharge in a watercourse by capturingflow near the peak of thehydrograph and therefore offers minimalopportunities for enhancement of stormwaterquality. Stormwater qualityenhancement deals with managing flow atthe beginning of the ascending limb of ahydrograph. Stormwater quality concernsand best management practices shall beaddressed/employed upstream of thefacility.Floodplain EncroachmentFor most reaches of the major watercourses inthe North Peoria ADMP study area, the floodplainand floodway are coincident due to thechannel and floodplain geometry in the deep,narrow canyons, and the floodway modelingtechniques used for the floodplain delineationstudies. Therefore, in reaches where thefloodway and floodplain are coincident, it isunlikely that any floodplain encroachmentwill occur. The majority of the wider floodwayfringe areas in the study area occur on CaterpillarTank Wash, Twin Buttes Wash, and theTwin Buttes Wash tributaries.Where floodway fringe areas exist in theNorth Peoria ADMP study area, floodplainencroachment should be avoided exceptwhere it meets the low-impact criteria definedbelow. Encroachment that exceeds the lowimpactcriteria should be allowed only whereit can be demonstrated that no long-term orshort-term off-site impacts to channel stabilityoccur, the encroachment is adequately protectedfrom erosion and flooding, and a longtermmaintenance and inspection program isadopted.34
- Page 2 and 3: TABLE OF CONTENTSPreface ..........
- Page 4: PREFACEAt the request of the City o
- Page 8 and 9: LIST OF TABLESTable 1: Regional and
- Page 10 and 11: INTRODUCTIONThe natural physical ch
- Page 12 and 13: minimize the effect of urbanization
- Page 14 and 15: Peoria General PlanThe Peoria Gener
- Page 16 and 17: HYDRAULICS8QQDPHG:DVK%LJ6SULQJHydra
- Page 18 and 19: FLOOD AND EROSION HAZARD ZONESWith
- Page 20 and 21: ing them before they are destroyed
- Page 22 and 23: PUBLIC INVOLVEMENTAn integral part
- Page 24 and 25: hard pan, typically less than two f
- Page 26 and 27: Economic CriterionThe evaluation of
- Page 28 and 29: Table 4Summary of Evaluation Result
- Page 30 and 31: INTRODUCTIONRULES OF DEVELOPMENTCom
- Page 32 and 33: Objective EH1.3Identify erosion haz
- Page 34 and 35: the purpose of watershed and waterc
- Page 36 and 37: the North Peoria ADMP. Users of the
- Page 38 and 39: (short, constricted reaches), backw
- Page 40 and 41: • Collect hydrologic data - peak
- Page 44 and 45: Low Impact Structural AlternativeFo
- Page 46 and 47: ack at the natural channel bed. In
- Page 48 and 49: stability, and to assure structure
- Page 50 and 51: developed for the Estrella Roadway,
- Page 52 and 53: gabion mattressA gabion mattress is
- Page 54 and 55: Maricopa County, August 21, 1993, H
- Page 70 and 71: 100-year W.S. ElevationBufferFEMA 1
- Page 72 and 73: NORTH PEORIA AREA DRAINAGE MASTER P
- Page 74: 100-year W.S. ElevationFEMA 100-yea
NORTH PEORIAAREA DRAINAGE MASTER PLANThe armored length <strong>of</strong> the structureshould be sufficient to eliminate development<strong>of</strong> a scour hole downstream <strong>of</strong> thestructure.• Lateral Weir. The lateral weir must besized such that the remaining peak flowand total run<strong>of</strong>f volume is equivalent toexisting conditions for the design storm.The weir crest elevation must be sufficientlyhigh enough to eliminate potentialbackwater conditions caused by the pondedwater in the basin that would reducethe efficiency <strong>of</strong> the weir. The potential forscour at the downstream toe <strong>of</strong> the weirmust be addressed. Sediment depositionwithin the channel at the toe <strong>of</strong> the weircould significantly alter the hydraulicoperation <strong>of</strong> the weir and thus the basin.Sediment deposition at the toe <strong>of</strong> the weirmust be regularly removed.• Drain Time. The basin must be drainedwithin 36 hours after the end <strong>of</strong> the designstorm. To accomplish this, it may be necessaryto provide a small bleed-<strong>of</strong>f culvert.For this situation, the minimum practicalculvert size should be used. Designguidelines for culverts must also be consideredand those guidelines are presentedin subsequent sections.• Basin Volume. The storage volume that isrequired must consider the potential loss<strong>of</strong> storage due to sediment deposition.Sediment deposition could potentiallyimpact the hydraulic operation <strong>of</strong> thebasin ultimately effecting the maximumwater surface elevation. The storage volumemust also be checked in conjunctionwith the embankment height in regard tothe jurisdictional classification. Structuresthat meet jurisdictional dam classificationrequirements must be designed in conformancewith ADWR requirements, andthe design must be approved by ADWR.Jurisdictional classification is discussedpreviously in the earthen dam guidelinesection.• Downstream Impacts. Hydrologic modelingshall be done to determine if thedetainment <strong>of</strong> run<strong>of</strong>f or the increased run<strong>of</strong>fdue to development worsens existingconditions. Modeling <strong>of</strong> multiple stormfrequencies may be required.• An in-stream, <strong>of</strong>f-line retention basin reducespeak discharge in a watercourse by capturingflow near the peak <strong>of</strong> thehydrograph and therefore <strong>of</strong>fers minimalopportunities for enhancement <strong>of</strong> stormwaterquality. Stormwater qualityenhancement deals with managing flow atthe beginning <strong>of</strong> the ascending limb <strong>of</strong> ahydrograph. Stormwater quality concernsand best management practices shall beaddressed/employed upstream <strong>of</strong> thefacility.<strong>Flood</strong>plain EncroachmentFor most reaches <strong>of</strong> the major watercourses inthe <strong>North</strong> <strong>Peoria</strong> ADMP study area, the floodplainand floodway are coincident due to thechannel and floodplain geometry in the deep,narrow canyons, and the floodway modelingtechniques used for the floodplain delineationstudies. Therefore, in reaches where thefloodway and floodplain are coincident, it isunlikely that any floodplain encroachmentwill occur. The majority <strong>of</strong> the wider floodwayfringe areas in the study area occur on CaterpillarTank Wash, Twin Buttes Wash, and theTwin Buttes Wash tributaries.Where floodway fringe areas exist in the<strong>North</strong> <strong>Peoria</strong> ADMP study area, floodplainencroachment should be avoided exceptwhere it meets the low-impact criteria definedbelow. Encroachment that exceeds the lowimpactcriteria should be allowed only whereit can be demonstrated that no long-term orshort-term <strong>of</strong>f-site impacts to channel stabilityoccur, the encroachment is adequately protectedfrom erosion and flooding, and a longtermmaintenance and inspection program isadopted.34
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