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A technique for determining depths for T-year discharges in rigid-boundary channels

Water-Resources Investigations Report 77-83

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Abstract

A simplified technique is presented for determining depths for T-year discharges (the discharge that will occur, on an average, once in T-years--10 years, 50 years, 100 years) for natural channels (channels not significantly affected by manmade structures) having channel-control conditions and rigid boundaries (channels having a low probability of change that would significantly affect the hydraulic characteristics of a T-year discharge). Channel-control conditions usually exist during T-year discharges in natural rigid-boundary channels and, therefore, the simplified technique probably would be applicable for flood-inundation studies for many natural rigid-boundary channels. The technique requires that the T-year discharge for a reach be known or readily available; also, a channel-shape factor, a width at a reference altitude, a channel-bottom slope (or a water-surface slope), and the Manning 's roughness factor, n, must be estimated or determined at representative sections having channel-control conditions. The standard error of estimate for depths determined according to the simplified technique is probably 25-30 percent. In comparison, the standard error of estimate for the depths determined according to the step-backwater procedure and to guidelines and specifications for flood-insurance studies of the Federal Insurance Administration is about 23 percent. (Woodard-USGS)

Additional Publication Details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
A technique for determining depths for T-year discharges in rigid-boundary channels
Series title:
Water-Resources Investigations Report
Series number:
77-83
Edition:
-
Year Published:
1977
Language:
ENGLISH
Publisher:
U.S. Geological Survey, Water Resources Division,
Description:
iv, 38 p. :ill., maps ;27 cm.