Laserfiche WebLink
<br /> <br />TIME OF CONCENTRATION CALCULATION COEFFICIENTS <br />TR-56 (19861 <br />Sheet Flow Travel tune <br />0 $ Where: T, =travel lime (min); n' =roughness coefficient: L =flow <br />0.007 ~n L <br />'[t = 0 ~ P= = 2-yr storm depth (inches); s =slope (fVft) <br />0.4 <br />~P2 ~ S Flow velocity = U(60T~ <br /> roughness <br />Flow Type Surface Type coefficient n': Surface Descrlpton <br /> A 0.011 Smooth surfaces (concrete, asphalt, gravel, bare soil) <br />c B 0.05 Fallow (no residue) <br />LL C 0.06 Cultivated soils: Residue rover <= 20% <br />~ ~ D - 0.17 Cultivated soils: Residue cover > 20% - <br />z E 0.15 Grass: Short grass prairie <br />. G F 0.24 Grass: Dense grasses <br />a G ~ 0.41 Grass: Bermuda grass <br />e° ~ H 0.13 Range (natural) <br />y I 0.40 Woods: Ught underbrush <br /> J 0.60 Woods: Heavy underbrush <br />Shallow Concentrated Flow Velocity <br />v = mS ~ Where: v =velocity (fps); m =roughness cceffienL S =slope (R/f <br /> roughness <br />Flow Type Surface Type coefficient m: Surface Description <br /> <br />c ~~ 3 <br />0 P - 20.3262 Paved <br />a~i"` <br /> U ~ 16.1345 Unpaved <br />luard (1946). SEDCAD (19921 Flow Velocities <br />v = aS Where: v =velocity (fps): a =roughness coeffient; S =slope (fUft <br /> roughness <br />Flow Type Surface Type coefficient a: Surace Description <br /> 1 2.5 Forest w/ heavy ground litter 8 Hay; meadow <br />o Trash Fallow; Minimum Tillage 8 Contour: strip cropped 8 <br />~ 2 5.1 Woodland <br /> 3 7.0 Short Grass <br />e 4 8.6 Straight row cultivation <br />C 5 10.1 Bare; unfilled <br /> 7 20.3 Paved <br /> <br />o u 5 10.t Alluvial fans <br />; <br />o <br />LL <br />r 6 16.1 Grassed waterways <br />to V <br /> 7 20.3 Small upland gullies <br />e <br />~ o <br />S <br />30.2 <br />Large gullies, diversions, shallow flowing streams <br /> <br />Z LL <br />V 9 93.3 Small stream flowing bank full <br />6/2712001 Golder Associates Inc 1 of 1 <br />