The following roughness coefficients for overland flow were suggested by the US Army Corps of Engineers in the Flood Runoff Analysis Engineering Design Manual, EM 1110-2-1417, August 1994.


Surface

n Value

Asphalt & concrete

0.05 - 0.15

Bare packed soil free of stone

0.10

Fallow - no residue

0.008 - 0.012

Conventional tillage - no residue

0.06 - 0.12

Conventional tillage - with residue

0.16 - 0.22

Chisel plow - no residue

0.06 - 0.12

Chisel plow - with residue

0.10 - 0.16

Fall disking - with residue

0.30 - 0.50

No till - no residue

0.04 - 0.10

No till (20 - 40 percent residue cover)

0.07 - 0.17

No Till (60 - 100 percent residue cover)

0.17 - 0.47

Sparse rangeland with debris:


0 percent cover

0.09 - 0.34

20 percent cover

0.05 - 0.25

Sparse vegetation

0.053 - 0.13

Short grass prairie

0.10 - 0.20

Poor grass cover on moderately rough bare surface

0.30

Light turf

0.20

Average grass cover

0.40

Dense turf

0.17 - 0.80

Dense grass

0.17 - 0.30

Bermuda grass

0.30 - 0.48

Dense shrubbery and forest litter

0.40