Analyzing the Impact of Impervious Area Disconnection on Urban Runoff Control Using an Analytical Probabilistic Model

The rapid spreading of impervious areas has been a growing concern in urban stormwater management. Runoff originating from impervious areas directly connected to or disconnected from drainage systems contributes differently to the outflow at the downstream outlet. Extensive implementations of best management practices (BMPs) and low impact development (LID) practices necessitate more accurate quantifications of the runoff control effects of disconnecting impervious areas from drainage networks. An analytical probabilistic model was developed in this study that considers the differences between directly-connected and disconnected impervious areas. The novel feature of this model is that it can not only explicitly consider the effect of impervious area disconnection but also analytically calculate the runoff reduction effects contributed by impervious area disconnection. Model validity is demonstrated by comparing its outcomes with the results of a series of continuous simulations for cases with different types of soils and various land use parameters in Jackson, Mississippi and Billings, Montana, USA. Example applications of the proposed analytical model also demonstrate its usefulness in the planning and design of impervious area disconnections.