Applications of Unit Hydrographs Good Forest Cover Soils Group C B 30% Forest 60% Meadow 10% Residential ½ Acre Soils Group B C 60% Residential ¼ acre 20% Commercial & Business 20% Open Space Soils Group D S=20% S=3% L=4 mi A C A=3 mi2 L=3.5 mi O J L=3 mi A=5 mi2 B A=4 mi2 S=10% Travel time J to O, 45 min Evaluate the Hydrograph Using SCS methods Location – Salt Lake City area

Steps Evaluate average CN for each watershed Evaluate tp for each watershed using 2-18 Evaluate TR, B and Qp Determine SCS unit hydrograph for each Determine initial abstraction and infiltration losses Determine design rainfall hyetograph and subtract losses (http://hdsc.nws.noaa.gov/hdsc/pfds/) Determine hydrograph using convolution