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Curve Number for mulch

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m2520840

Civil/Environmental
Joined
Jan 17, 2007
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2
Location
US
Where can i find CN for mulch in soil group D?

Thank you.
 
At best, this might approximate "Open space, good condition, grass cover >75%" with a CN of 80. (From the TR-55 CN tables, HSG D)

Worst case is likely to be "...poor condition, grass cover <50%" with a CN of 89. (Same CN as HSG-D dirt roads.)

The exact type, depth, and condition of the mulch will defintitely influence where you fall in this range. But you may need to base the design on the worst-case (maximum) CN.
 
Mulch floats so you really have to check your design storm. Unless your mulch is anchored I might skip it unless you are worried about very small events. In this case I would use an initial abstration which will be dependent on the thickness of the mulch. For (limited) humor, worst case you should bulk your flows.
 
I can't imagine a large enough mulched area for the CN to be critical. It's not like one mulches a 10 acre field, but usually landscaping.

I would be tempted to use a CN for Woods (thin stand) as in winter the conditions, certainly in deciduous areas, are a thick leaf mulch bed.
 
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