Evaluating effects of urban imperviousness connectivity on runoff with consideration of receiving pervious area properties

Reducing imperviousness connectivity by low impact developments or receiving pervious area (RPA) has been a regular strategy for runoff mitigation. However, the effects of RPA properties in combination with imperviousness connectivity on runoff have not been fully discussed. In this study, two kinds of RPA are defined according to ponding volume: retention-dominated and conveyance-dominated. Runoff for a small urban catchment was evaluated under scenarios with varying imperviousness connectivity, rainfall condition and initial soil saturation by the Storm Water Management Model. The results present significant runoff mitigation for imperviousness disconnecting by the retention-dominated RPA. However, imperviousness disconnecting by the conveyance-dominated RPA may conversely lead to higher peak runoff. Increased initial soil saturation weakens the effectiveness of runoff mitigation for the retention-dominated RPA, but has limited effects for the conveyance-dominated RPA. This study emphasizes the role of RPA properties in addition to indicators evaluating imperviousness only in urban planning.