SURFACE-WATER FIELD TECHNIQUES

Verified Roughness Characteristics of Natural Channels

Most hydraulic computations related to indirect estimates of discharge require an evaluation of the roughness characteristics of the channel. In the absence of a satisfactory quantitative procedure this evaluation remains chiefly an art. The ability to evaluate roughness coefficients must be developed through experience. One means of gaining this experience is by examining and becoming acquainted with the appearance of some typical channels whose roughness coefficients are known.

The photographs and data linked to this page represent a wide range of channel conditions found in the Western United States. Familiarity with the appearance, geometry, and roughness characteristics of these channels will improve your ability to select roughness coefficients for other channels. We will contiune to link descriptions of additional sites to this page as verification data become available. (Text above modified from USGS Water Supply Paper 1849, by H.H. Barnes, Jr.))

You can view data related to selected roughness coefficients by clicking on a site name, or photo, below:

Manning's n-value	Stream	Photo Photo 1 Photo 2
0.024	Columbia River at Vernita, Washington
0.028	Clark Fork at St. Regis, Montana
0.030	Clark Fork above Missoula, Montana
0.032	Salt River below Stewart Mountain Dam, Arizona
0.033	Clearwater River at Kamiah, Idaho
0.036	West Fork Bitterroot River near Conner, Montana
0.037	Wenatchee River at Plain, Washington
0.038	Moyie River at Eastport, Idaho
0.038	Spokane River at Spokane, Washington
0.041	Middle Fork Flathead River near Essex, Montana
0.043	Catherine Creek near Union, Oregon
0.043	Chiwawa River near Plain, Washington
0.043	Grande Ronde River at La Grande, Oregon
0.045; 0.073	Provo River near Hailstone, Utah
0.050	Clear Creek near Golden, Colorado
0.051	South Fork Clearwater River near Grangeville, Idaho
0.053; 0.079	Cache Creek near Lower Lake, California
0.057	Mission Creek near Cashmere, Washington
0.060	Rock Creek Canal near Darby, Montana
0.065	Merced River at Happy Isles Bridge, near Yosemite, California
0.073	Boundary Creek near Porthill, Idaho
0.075	Rock Creek near Darby, Montana	(Missing)