Pattern of flood peak increase in urbanizing basins with constant and variable slopes

Abstract

A kinematic-wave based computer model has been used to examine the effect of basin slope on the increase in flood peak due to urbanization. The degree of urbanization is expressed in terms of percentage area made impervious, and percentage area served by storm sewers. The study covers basins with constant slope as well as variable slopes. In the latter case, the basin slope steepens progressively from downstream to upstream sub-basins. The results show that as urbanization progresses from downstream to upstream, there is an accelerated rate of increase in flood peak for basins with constant slope; as opposed to a decelerated rate of increase in flood peak for basins with variable slope. In addition, for the case with constant basin slope, the increase of peak flow due to urbanization is greater for the basin with a steeper slope. While the impervious and sewered areas have comparable effect on the increase of flood peak for basins with constant slope, the effect of impervious area is much greater than that of sewered area for the basin with variable slopes.