HEC HMS Preprocessor
User Manual
Contact Project Planning (951) 955-1200
Watershed Area sq mi
1 Hour Storm
Point Precipitation  in.
Areal Adjustment Factor  %
Adjusted Point Precipitation
Slope of Rainfall Intensity - Duration Curve
3 Hour Storm
Point Precipitation  in.
Areal Adjustment Factor  %
Adjusted Point Precipitation
6 Hour Storm
Point Precipitation  in.
Areal Adjustment Factor %
Adjusted Point Precipitation
24 Hour Storm
Point Precipitation  in.
Areal Adjustment Factor  %
Adjusted Point Precipitation
Refer to Plate E-5.8
Lag Time Calculator
Basin Factor - n
Length along longest watercourse - L ft
Length along longest watercourse measured upstream to a point opposite the centroid of the area - Lca ft
Elevation Difference ft
Lag Time hr
40% Lag Time min

          
Add Loss Rate Values
    AMC Condition: 
Soil Group / Cover Type View Chart RI Number Perv. Area Infiltrn Rate (in/hr) Land Use Imp. Area Decimal % Adj.Infiltrn Rate (in/hr) Area (acres)    
           

Soil Group / Cover Type RI Number Perv. Area Infiltrn Rate (in/hr) Land Use Imp. Area Decimal % Adj.Infiltrn Rate (in/hr) Area (acres) Area/ Total Area Ave. Adj. Rate (in/hr)
Total area =
Average Soil Loss =