Unsaturated Flow Functions for Filter Media Used in Low-Impact Development—Stormwater Management Systems

Abstract

Moisture retention relationships for coarse, high-infiltration soils are difficult to empirically determine and estimate. Present day software models for stormwater management (SWM) that are used as sizing and performance prediction tools for filtration Low Impact Development-Stormwater Management (LID-SWM) systems typically assume that these systems function under saturated flow conditions. This directly impacts prediction of system drainage and hydrographs, as well as the estimates of physically-based water quality improvement. Yet real-time monitoring of these systems demonstrated that saturation of the filter media is rarely achieved. This article presents a framework for obtaining the moisture retention curves (MRC) and relative hydraulic conductivity