1. 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

2. 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 (
Determine hydrograph using convolution