Water Resources Engineer Wright Water Engineers, Inc.
This presentation will discuss a project that monitored the performance of multiple different receiving pervious areas (RPAs) in Colorado. The project was initiated and funded by the several Colorado organizations (Southeast Metro Stormwater Authority, Mile High Flood District, Cherry Creek Basin Water Quality Authority) due to the importance of RPAs in reducing runoff. For this project, we measured the performance of several types of RPAs (grass swales, vegetated buffers and infiltration basins) using simulated runoff tests (SRTs) and monitoring of rainfall-runoff events. SRTs applied water to the RPAs from fire hydrants to provide high-quality estimates of inflow rates and volumes compared to rainfall-runoff estimates. Weir boxes were installed on grass swale underdrains to measure the discharge rate and volume to determine runoff reduction. For RPAs without underdrains, the surface area (grass buffers) and storage volume (infiltration basins) required to capture and infiltrate the inflow was measured using high-resolution survey data. Rainfall-runoff events were monitored using time-lapse cameras to determine minimum rainfall depths and intensities that were captured and infiltrated through the RPAs. Results show that the performance of RPAs is highly-variable, with some sites demonstrating better-than-expected runoff reduction and other sites demonstrating little to no runoff reduction. We will discuss the methods of the study (some of which are novel), explain reasons for the variable results and discuss implications for the future design and construction of RPAs to improve their performance.
