Testing the Efficacy of Empirical Equations for Calculating the Effective Impervious Area in Southern California

Abstract

The effective impervious area (EIA) is the portion of the total impervious area (TIA) that is hydraulically connected to the storm drainage network; thus, it is responsible for a majority of the runoff and its adverse effects in watersheds. Empirical equations for determining EIA are frequently used since they are quick and easy to use, but their accuracy has been untested in the Southern California region. The goals of this study are to: (1) test the accuracy of empirical equations on watersheds within the Southern California region (2) develop an EIA equation for the region based on the EIA vs. TIA relationships (3) Calibrate a stormwater management model using the TIA and EIA values from the equations and see how they perform compared to the measured hydrograph. The results will help inform planners and engineers of the effectiveness of utilizing EIA empirical equations for Best Management Practices (BMP) structures and stormwater conveyance system sizing in the region.