Runoff Curve Number
Runoff Curve Number
(OP)
I'm trying to find a curve number (CN) to use in a watershed anlyses using TR-55 (HydroCAD) for broken pavement. Any suggestions?
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RE: Runoff Curve Number
To be conservative, I'd probably use 98 (assume no breaks). The curve numbers for gravel for types A, B, C & D soil, respectively, are: 76, 85, 89 & 91. I've never come across a type A soil, and most clay soils are type C. Building rubble would definitely be type D, so perhaps a number in the region of 92-96 would be appropriate.
Depending on the area of broken paving, you may find that there is little difference in the amount of runoff between using 98 and interpolating a CN.