Calculator to Estimate Annual Infiltration Performance of Roadside Swales

Abstract

Roadside swales or drainage ditches are low-impact development (LID) practices for stormwater treatment and control, and there is a need to quantify their infiltration performance for design and planning purposes. A roadside swale calculator has been developed where only the main design parameters that have a significant impact on the runoff volume output are required, in addition to the rainfall distribution of the study site. The inputs of the calculator are the saturated hydraulic conductivity of the soil, width of the swale, width of the road, and location’s rainfall frequency or volume percentile. The calculator and the ancillary information provided can be used to determine: (1) the total percentage of annual volume infiltrated, (2) the percentage of events entirely captured by a roadside swale in a year, and (3) the percentage of road runoff infiltrated by a roadside swale with a specific swale width-to-road width ratio and saturated hydraulic conductivity for a given rainfall depth event.