Hydrologic Performance of a Multicell Vegetated Basin with Different Soil and Outlet Structure Characteristics

Abstract

Green stormwater infrastructure, also known as stormwater control measures (SCMs), is a sustainable solution that has been widely used in controlling stormwater runoff in developed areas. Stormwater intensity and land use control the water quality and quantity in urban areas, while soil conditions and the functionality of the outlet structure control enhancement of the water quality and quantity in vegetated basins. The soil conditions and the outlet structure are dubbed geotechnical design characteristics. These parameters impact the basin’s infiltration capacity, volume, and peak flow. In this study, a multistage basin with three cells located at the Pennypack Creek headwaters in Pennsylvania was simulated using the Stormwater Management Model (SWMM). The investigated characteristics of the basin were the gate condition and pipe diameter of the outlet structure and the compaction condition of the soil. The model was calibrated considering opened- and closed-gate setup of the basin. The basin was unintentionally compacted during construction, and this compaction changed the infiltration properties of the basin from sandy loam soil (preconstruction) to sandy clay loam. After basin calibration, it was found that the closed-gate setup induced a high outflow reduction compared to the inflow. A parametric study considering both the outlet pipe diameter and soil type was conducted under both gate setups. The reduction of the outlet pipe diameter was the most effective characteristic in the outflow volume and flow peak reduction under the opened-gate setup, while the soil type was the most effective characteristic in the outflow volume and flow peak reduction under the closed-gate setup.