Urban Runoff Simulation Model

Abstract

A study to determine the sensitivity of the unit hydrograph to the effects of the urbanization process was conducted. The overland flow parameter that defines the degree of urbanization in an urban watershed is the percentage of the total watershed area that is impervious. Furthermore, the parameter which defines the degree of urbanization in the channelized flow portion of a watershed is the channel roughness coefficient. Several rainfall‐runoff simulations were conducted in order to determine the hydrologic response of the unit hydrograph to the impact of urbanization. A hydrologic model was formulated for an urban catchment located at Houston, Texas, using the kinematic wave model developed by the Hydrologic Engineering Center (HEC). The model was used to simulate various degrees of urbanization by allowing the percentage of watershed imperviousness and the channel roughness coefficient to vary from simulation to simulation. A system of regression equations was developed to quantify the impact of urbanization on the unit hydrograph. The equations were incorporated into the A&M Watershed Model and verified by modeling three test watersheds.