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Long Valley Creek:Long Valley Creek:A Rainfall-Runoff Modeling A Rainfall-Runoff Modeling
StoryStory
Rob ThompsonRob ThompsonHydrologistHydrologist
U.S. Army Corps of EngineersU.S. Army Corps of EngineersSacramento DistrictSacramento District
[email protected]@usace.army.mil
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Reno/Truckee Reno/Truckee Meadows Flood Meadows Flood Control ProjectControl Project
Long Valley Long Valley CreekCreek
WatershedWatershed
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Truckee Meadows 1997Truckee Meadows 1997Truckee Meadows 1997Truckee Meadows 1997
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Long Valley Creek Model Long Valley Creek Model MethodologyMethodology
Feasibility studyFeasibility study Available data: one USGS peak flow gage and a Available data: one USGS peak flow gage and a
nearby rain gage.nearby rain gage. Gage: limited period of recordGage: limited period of record Correlated 2-day precipitationCorrelated 2-day precipitation to peak flow to extend recordto peak flow to extend record
Rainfall-Runoff ModelRainfall-Runoff Model Parameters physically basedParameters physically based
Gathered from maps, GIS, Gathered from maps, GIS, soil surveys, previous studiessoil surveys, previous studies
Model (loss rates) calibratedModel (loss rates) calibrated to frequency curveto frequency curve
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HEC-1 vs HEC-HMSHEC-1 vs HEC-HMS
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Rainfall-Runoff ModelingRainfall-Runoff Modeling
1.1. Characterize WatershedCharacterize Watershed
2.2. Develop PrecipitationDevelop Precipitation
3.3. Account for LossesAccount for Losses
4.4. Transform to Runoff HydrographTransform to Runoff Hydrograph
5.5. Route Hydrographs through the Route Hydrographs through the WatershedWatershed
6.6. Combine HydrographsCombine Hydrographs
The ProcessThe Process
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Basin CharacterizationBasin Characterization
GEO-HMSGEO-HMS 11 Subbasins11 Subbasins Geometry:Geometry:
CentroidCentroid Centroidal Flow Centroidal Flow
PathPath Longest Flow Longest Flow
PathPath SlopeSlope Basin AreaBasin Area
Long Valley Creek, NVLong Valley Creek, NV
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Design StormsDesign Storms
NOAA 14 precipitation frequency dataNOAA 14 precipitation frequency data 5- through 500-year events (7 5- through 500-year events (7
Frequencies)Frequencies) Storm centering to maximize peak Storm centering to maximize peak
runoffrunoff Areal Reduction FactorsAreal Reduction Factors Pattern Hyetograph -- Reno January Pattern Hyetograph -- Reno January
1963 Storm1963 Storm Balanced to 1, 3, 6, 12, 24 hour depthsBalanced to 1, 3, 6, 12, 24 hour depths
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NOAA 14NOAA 14http://hdsc.nws.noaa.gov/hdsc/pfds/index.htmlhttp://hdsc.nws.noaa.gov/hdsc/pfds/index.html
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Depth Area Reduction Depth Area Reduction FactorsFactors
12-Hour DARF = 0.01*(100-7.0*Area0.46)
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24-Hour Pattern (Reno Jan 1963)
0.000
0.100
0.200
0.300
0.400
0.500
0.600
0.700
0.800
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Time (hrs)
Rain
fall (
in)
24-Hour Balanced 100-Year Storm
0.000
0.100
0.200
0.300
0.400
0.500
0.600
0.700
0.800
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Time (hrs)
Rain
fall
(in
)Peak 1 Hour
Peak 1 Hour
Peak 3 Hour
Peak 3 Hour
Peak 6 Hour
Peak 6 Hour
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Loss RatesLoss Rates Initial and ConstantInitial and Constant
Initial Initial Initial losses set to 0Initial losses set to 0
ConstantConstant NRCS Soil Survey NRCS Soil Survey
DataData Long Valley Creek Long Valley Creek
> 75% D Type Soils > 75% D Type Soils Calibrated to Freq. Calibrated to Freq.
CurveCurve Percent ImperviousPercent Impervious
5%5%
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Used LA Unit Hydrograph Procedure with Used LA Unit Hydrograph Procedure with S-graph from Truckee Meadows S-graph from Truckee Meadows
Computed lag from basin geometryComputed lag from basin geometry
User Generated Unit User Generated Unit HydrographsHydrographs
LL = Length of Longest = Length of Longest Stream Stream CourseCourseLcaLca = Centroidal Stream = Centroidal Stream LengthLengthSS = Slope ( = Slope (ΔΔElevation/L)Elevation/L)nn = Basin “n” – watershed = Basin “n” – watershed roughness roughness factorfactor
Lag = 24n{[(L x Lag = 24n{[(L x Lca)/(S^.5)]^.38}Lca)/(S^.5)]^.38}
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RoutingRouting&&
CombininCombiningg
Muskingum Routing
Routing Time (K)Stream Velocity
Muskingum XVaries from 0 to 0.5Slope, Roughness
K < 1 hourX = 0.35
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CalibrationCalibration
Loss rates adjusted for each event to Loss rates adjusted for each event to match frequency curvematch frequency curve
Larger event = lower loss ratesLarger event = lower loss rates
EventConstant Loss
Rate
10 year 0.16
50 year 0.13
100 year 0.10
200 year 0.08
500 year 0.04
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End ResultsEnd Results
HydrographsHydrographs
FloodplainFloodplain
Results—Final Results—Final HydrographsHydrographs