Hydrology
A composite Rational Method C value from your boundary and land use.
Overlay your drainage-area boundary on land-use polygons and get an area-weighted runoff coefficient C you can use for storm sewer, inlet and rational-method sizing.
C-Calculator
Free with an account
How it works
- Upload the drainage boundary (DXF) and land-use shapefile.
- KAPPS overlays them and weights C by area.
- Download the results ZIP.
What goes in, what comes out
You provide
- Drainage area boundary .dxf
Polylines defining each drainage area you want a C value for. - Land-use layers .shp + .shx + .dbf + .prj
One shapefile per land-use category. The filename (without extension) drives which runoff coefficient is assigned — see the reference table below for the accepted keys.
You get
- Rational C results .zip (contains shapefile)
A shapefile with one feature per drainage area: DA_ID, acreage by land-use column, Total_Area, and Comp_C (the weighted composite C value).