Framework for Investigating the Impact of Distribution, Quantity, and Infiltration and Outlet Design Characteristics of Vegetated Basins in the Headwaters of a Watershed

Abstract

Vegetated basins are one type of stormwater control measure (SCM) that uses a depression to control runoff volume and enhance water quality. Within this depression, the infiltration and outflow are affected by the infiltration and outlet design characteristics (IODCs) of the basin such as the soil compaction and outlet structure conditions (e.g., opened or closed outlet, and pipe diameter). The distribution of many vegetated basins can mitigate runoff volume to reduce flooding within watersheds. Thus, it is essential to investigate the influence of basin quantity, distribution, and IODC on storm runoff volume, peak flow, and infiltration within watersheds. This study evaluated the influence of vegetated basin quantity, distribution, and IODCs on watershed-scale volume reduction, peak flow attenuation, and stream health using a spatial, hydraulic, and hydrologic framework. One multistage basin with three basins in series located at the Pennypack Creek headwaters in Pennsylvania was simulated using the Storm Water Management Model (SWMM). Then the basins were distributed in different quantities in the three headwater regions using ArcGIS tools. The most effective basin distribution and quantity pattern was used to conduct a parametric study considering different IODCs. The results showed that increasing the quantity of basins within all the headwater regions provided the maximum improvement to the stream volume reduction and peak flow attenuation in the watershed, 31% and 61%, respectively, during a single storm event. This volume reduction also was sensitive to the variation in the IODCs of the basins. Maintaining a fully closed outlet for the watershed basins increased the volume reduction by 78%. Maximizing the number of basins in a headwater can improve the health of receiving water bodies by effectively reducing the percentage of imperviousness. This study provides a framework for utilizing the simulation of a single SCM’s geotechnical and volume control properties using SWMM to optimize the location and quantity of SCMs within watersheds using ArcGIS.