Performance of a Hydraulically Linked and Physically Decoupled Stormwater Control Measure (SCM) System with Potentially Heterogeneous Native Soil

Abstract

This study shows that a physically decoupled but hydraulically linked design focusing on surface infiltration components (i.e., excluding underdrain and infiltration bed systems) can be the preferred way to have a low-cost and robust stormwater control measure (SCM) system. The SCM under investigation in Philadelphia, PA, is a green infrastructure (GI) and has a mirrored design of two sets of hydraulically linked planters. Each planter has an overflow pipe connected to an underground infiltration bed. The system showed excellent overall performance as no overflow/bypass entering the combined sewer. A large variation of saturated hydraulic conductivity was found for the planter soil, and the planter with lower saturated hydraulic conductivity created surface runoff that overflows to the next planter in line. Due to the linked design, the unexpected deviation of performance of a single planter did not affect overall system performance. The infiltration bed showed great variation in water drawdown rate at different water depth, which could be caused by the possible high heterogeneity of the native soil. The study argued that overflow systems, which handled only about 18% of runoff in this study, can be replaced by slightly larger surface area for lower building cost, lower maintenance cost, and more reliable performance.

Methodology to simulate unsaturated zone hydrology in Storm Water Management Model (SWMM) for green infrastructure design and evaluation

“…There are other benefits of GI including mitigating water quality, promoting soil infiltration, promoting human health, promoting ecosystem services, mitigating air quality, and mitigating the urban heat island effect [1][2][3][4][5][6][7]. Recognizing the benefits of GI, many cities have started to adopt various types of GI at the city-wide scale [8][9], however, there remains a need for models that represent the vadose zone hydraulics to aid in design and understanding of system behavior. For example, water uptake by plant roots is an important part of GI function [10][11][12] and can depend on both soil moisture [13][14] and depth-dependent root density [15].…”