ESTIMATING RUNOFF VOLUMES FROM URBAN AREAS¹

Abstract

ABSTRACT: Estimations of runoff volumes from urban areas can be made by the equation Q = a A σ(P e – b), where Q is the runoff volume, a is the part of the total area A Contributing to runoff, P e is the rainfall amount for a single event, and b is the initial rainfall losses. For the evaluation of a and b, rainfall/runoff measurements were made in five areas of sizes between 0.035 km 2 and 1.450 km 2 . By linear regression analysis of rainfall volumes versus runoff volumes, the initial rainfall losses were found to vary from 0.38 mm to 0.70 mm for the different areas. The parts of the areas contributing to runoff were found to be proportional to the impermeable parts of the mas. The equation is applicable in urban areas with well defined paved surfaces and roofs and with a negligible amount of runoff from permeable areas.