New Methods for Quantifying Effective Impervious Area in Urban Watersheds (original) (raw)

Although total impervious area (TIA) has been traditionally used as an indicator of urban disturbance, recent studies suggest that a better indicator of urban runoff is the "effective" impervious area (EIA), or the portion of total impervious area that is hydraulically connected to the storm sewer system. EIA can be considered the most important parameter in determining urban runoff, and knowledge of EIA is therefore critical in rainfall-runoff modeling. The incorrect use of TIA instead of EIA in urban hydrologic modeling leads to an overestimation of runoff volumes and rates . Also, directly connected impervious areas are the primary contributing area for smaller storms and therefore, the main concern for water quality . The most accurate method for quantifying EIA in urban watersheds is supposed to be the statistical analysis of rainfall-runoff data sets , because it is based on observed data. Without a good comparison to EIA determined from rainfall and runoff data, the other techniques to measure EIA (e.g. GIS techniques) cannot be verified. Methods to improve estimates of EIA are not highly researched, and need further investigation.