Overland flow time of concentration on flat terrains

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Title: Overland flow time of concentration on flat terrains
Author: Chibber, Paramjit
Abstract: Time of concentration parameter is defined very loosely in literature and it is calculated rather subjectively in practice (Akan 1986 ) . The situation becomes adverse as the terrain slope approaches zero ; because the slope generally appears in the denominator of any formula for time of concentration , this time goes to infinity as the slope goes to zero . The variables affecting this time parameter on flat terrains have been studied through plot scale field experiments . It has been found that the antecedent moisture and rainfall rate control this parameter . Some of the existing time of concentration methods have been compared , and it is found that all the empirical models compared under predict this time parameter . This under prediction can be attributed first to the differing concepts of time of concentration previous researchers have modeled , secondly to the absence of any accounting for the initial moisture content in their respective equations and thirdly to the watersheds where these models have been calibrated . At lower time of concentrations , Izzard -based model predictions show some results close to the observed values . A methodology to determine the plot scale surface undulations has been developed to estimate the depression storage . Regression equations have been derived based upon the experiments to determine the overland flow times on a flat plot of 30 feet length with uniform rainfall intensity . The application of these equations on other lengths cannot be ascertained . Equations for the hydrograph slope on flat terrains have been determined for bare clay and grass plots .
URI: http : / /hdl .handle .net /1969 .1 /1293
Date: 2004-11-15

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Overland flow time of concentration on flat terrains. Available electronically from http : / /hdl .handle .net /1969 .1 /1293 .

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