CEVE 412/512 Dr. Phil Bedient Jan 2016 Hydrologic Analysis Hydrology and Floodplain Analysis Chapter 2 CEVE 412/512 Dr. Phil Bedient Jan 2016

Applications of Unit Hydrographs Hydrology and Floodplain Analysis, Chapter 2.4 Applications of Unit Hydrographs

UH Applications For complex watersheds: Design storm hydrographs (10-yr, 25-yr,100-yr) Historical rainfall events Evaluate effects of land use changes, channelization, storage additions, and other variables Simulate storm hydrographs (Ch. 4) Analysis of flood control options (Ch. 4)

UH Applications Design storm hydrographs (10-yr, 25-yr,100-yr)

Typical Design Rainfall Dist’n Design storm hydrographs (10-yr, 25-yr,100-yr) 10 yr – 7.35 in 25 yr – 9.51 in 100 yr – 13.89 in

UH Applications Design storm inches by duration (10-yr, 25-yr,100-yr) Developed by the NWS for all urban areas Duration 10 - yr 25 - yr 100 – yr 15 min 0.69 0.83 1.08 1 hr 2.76 3.33 4.32 3 hr 4.25 5.3 7.33 6 hr 5.27 6.76 9.82 12 hr 6.37 8.31 12.31 24 hr 7.35 9.51 13.89

UH Land Use Effects Effects of land use changes, storage additions, and other variables – normally increase peak flows

UH Conversion to Storm Hydr Create storm hydrograph from UH for each subbasin as function of rainfall Combine hydrographs at each confluence Flood route combined hydrographs downstream Add in additional runoff from subbasins Finally add together to get final storm hydrograph

Flood Routing – Reservoir & River Tends to shift hydrograph in time and reduce the flow Q S S Q Reservoir Routing River Routing

Hydrograph Watershed Analysis 1 2 3 3

Hydrograph Combining/Routing Subarea G + Subarea F = Combine PT1 1

Hydrograph Combining/Routing Subarea G + Subarea F = Combine PT1 Subarea E + Route to 3 + Subarea C = Combine PT3 1 1 3

Hydrograph Combining/Routing Subarea G + Subarea F = Combine PT1 Subarea E + Route to 3 + Subarea C = Combine PT3 Combine PT1 + Route to 2 + Subarea D = Combine PT2 2 3

Hydrograph Combining/Routing Subarea G + Subarea F = Combine PT1 Subarea E + Route to 3 + Subarea C = Combine PT3 Combine PT1 + Route to 2 + Subarea D = Combine PT2 Combine PT2 + Route to 3 + Subarea B = Combine PT3 2 3 4

Hydrograph Combining/Routing Combine PT3 + Route to 4 + Subarea A = RESULTING HYDROG 2 3 Q 4 T

Linear and Kinematic Wave Models Hydrology and Floodplain Analysis, Chapter 2.5 Linear and Kinematic Wave Models

Kinematic Wave Used to develop stream hydrographs and compute overland flow The Kinematic Wave is used because it assumes that the weight or gravity force is balanced by the resistive bed friction Has been integrated into HEC-HMS and can be used for Storm Water Management Models

Kinematic Wave Kinematic (kw) wave routing used to derive overland flow hydrographs Can be added to produce collector or channel hydrographs Then can be flood routed as channel or stream hydrographs.