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TechnicalMemorandum:Hydrologic&HydraulicStudyforTaylorBayou,HCFCUnitA1040000 <br />December13,2011 <br />Page3of6 <br />TaylorBayouanditstributariesaretidallyinfluencedwithoverbankareassubjecttoinundation <br />fromcoastalstormsurgesinGalvestonBay.TheShadyRiverSubdivisionwasconstructedinthemid <br />ϭϵϲϬ͛ƐpriortotheNationalFloodInsuranceProgram(NFIP)andtheavailabilityoffloodplainmaps <br />andflooddata.Basedonexistingtopography,thesubdivisionissusceptibletoinundationfrom <br />tropicalstormsproducingsurgeelevationsabove7feet.Itislikelythathomesconstructedinthe <br />ϭϵϲϬ͛ƐandϭϵϳϬ͛Ɛwouldbesusceptibletofloodinundationfromcoastalstormflooding. <br />FEMAEffectiveModels <br />TaylorBayou,HCFCUnitA1040000,isaFEMAstudiedstream.ThestudylimitsalongHCFCUnit <br />A1040000extendfromitsconfluencewithClearCreek,HCFCUnitA1000000,tojustupstreamof <br />ShoreacresBoulevard.TheFEMAeffectivehydrologic(HECHMS)modelandhydraulic(HECRAS) <br />modelforTaylorBayouwereobtainedfromtheHarrisCountyFloodControlDistrict.TheFEMA <br />effectivemodelsservedasthebaseconditionmodelsforthisstudy. <br />ItistheintentofthisstudytoextendtheFEMAeffectivehydraulic(HECRAS)modelforTaylor <br />Bayou,HCFCUnitA1040000,fromShoreacresBoulevardupstreamtoStateHighway146.In <br />addition,anewhydraulicmodelwasdevelopedforHCFCUnitA1041201fromitsconfluencewith <br />HCFCUnitA1040000toBayForestGolfCourse.ThestudylimitsarelocatedinSubareaA104A <br />(1998.72acres)oftheTaylorBayouwatershed.TheFEMAeffectivehydrologic(HECHMS)model <br />computedpeakflowsforthe10,50and100yearstormeventsforSubareaA104Aaslistedin <br />Table1. <br />Table1.FEMAEffectiveHECHMSModelforSubareaA104A <br />DrainageDAPeakFlow(cfs) <br />Subarea(acres)10Year50Year100Year <br />A104A1998.7293014231681 <br />RevisedHydrologic(HECHMS)Model <br />SubareaA104Awassubdividedintonine(9)subareas,identifiedasA104A1throughA104A9,to <br />computepeakflowsalongHCFCUnitA1040000andHCFCUnitA1041201.Therevised <br />watershedmapforSubareaA104AisshowninExhibit3.SubareasA104A1,A104A2,A104A3, <br />A104A4andA104A9weredelineatedforcontributingdrainageareastoTaylorBayou,HCFCUnit <br />A1040000.SubareasA104A5,A104A6,A104A7andA104A8weredelineatedforcontributing <br />drainageareastoHCFCUnitA1041201.ThehydrologiccomputationalnodesalongHCFCUnit <br />A1040000andHCFCUnitA1041201areshoweexhibit.TherevisedHECHMSmodel <br />ninth <br />resultsforTaylorBayou,HCFCUnitA1040000,arelistedinTable2. <br /> <br />