Performance Evaluation of a Regenerative Stormwater Conveyance System: Case Study in Knoxville, Tennessee

As communities throughout the world work to reduce the impacts of urban stormwater on receiving streams, new stormwater controls have been a welcome addition to the established suite of green infrastructure practices. One such innovative control is the regenerative stormwater conveyance (RSC), which has shown mixed performance based on a limited number of studies to date. In this study, an RSC was constructed in Knoxville, Tennessee, and monitored for water quality and hydrologic performance over a 16-month period. Although modest cumulative volume reductions (6% overall) were realized, performance was found to substantially vary by season. Specifically, during the growing season when vegetation is active and water tables are low, performance increased to a cumulative volume reduction of 29%. Although effluent pollutant concentrations (total suspended solids, ammonium, nitrate, phosphate, sulfate, copper, and zinc) were consistent with those reported in the literature, concentration reductions were limited, and performance only slightly improved when load reductions were considered (load reductions for all parameters ranged from -342% to 38%). This is predominately attributed to low inlet concentrations, and emphasizes the need to evaluate stormwater control effectiveness based on multiple criteria. The frequent export of total suspended solids at the site (-60% load reduction) also suggests that the pools were too shallow, and that optimization of this design feature is needed to minimize internal scour. This work emphasizes the influence of seasonal processes such as evapotranspiration, and antecedent site conditions such as water table elevation and soil saturation on RSC function. Specifically, the data indicate that performance of these systems is likely to be highest when the RSC's sandy media can drain between storms, allowing recuperation of storage volume. Additional research is needed to fully quantify RSC function and develop design criteria for RSCs under various site conditions.