Trend Assessment in Rainfall-Runoff Behavior in Urbanizing Watersheds

Abstract

A typical flood frequency analysis is based on gauged annual maximum discharges. One assumption behind the analysis is that the measured discharge signal is stationary. The validity of this assumption can be difficult to establish, particularly where urbanization has occurred within the gauged watershed, altering the response of the affected watershed to precipitation. This alteration can produce a nonstationary streamflow signal that can be significant, depending on the percentage of the watershed altered. As urbanization increases, peak discharges are shown to increase, producing a positive trend in the annual maximum series. Urbanization occurring during and/or after the gauging period is quantified using spatially and temporally distributed land use data. Three statistical tests (a parametric