Flow at Grade-Break from Mild to Steep Slopes

by Richard G. Weyermuller, (A.M.ASCE), Civ. Engrg. Assoc.; Dept.of Water and Power, City of Los Angeles, Calif.,
M. Gamal Mostafa, (M.ASCE), Prof.; Dept. of Civ. Engrg., California State Univ. at Long Beach, Long Beach, Calif.,

Serial Information: Journal of the Hydraulics Division, 1976, Vol. 102, Issue 10, Pg. 1439-1448

Document Type: Journal Paper


An empirical equation was determined using dimensional analysis and experimental test data to determine the depth of flow at a grade-break in a rectangular channel where the slope changes from mild to steep. The ratio of the depth of flow at the grade-break to the critical depth of flow was found to depend largely upon the slope of the downstream reach. The ratio reached a minimum of 0.715 when the downstream slope was steep enough to produce clear separation of the flow with an aerated nappe. The upper limit of 1.0 was approached as the downstream slope approached critical.

Subject Headings: Rivers and streams | Slopes | Critical flow | Empirical equations | Field tests | Channel flow | Flow separation | Aeration

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