Hydraulic modeling of regenerative stormwater conveyances

In natural systems, stormwater moves to streams and river networks by way of wetlands, floodplains, and riparian forests which offer treatment and runoff detention. As watersheds are urbanized, these natural flow paths are short circuited by storm drains and pipes that bypass these ecosystem services. This causes increased peak flows in receiving waters leading to erosion, decreased flood control, and water quality degradation. Regenerative stormwater conveyances (RSCs) are an emerging design solution to decrease runoff flow energy, increase infiltration rates, and improve water quality. Positioned at the stormwater outfall, RSCs are comprised of an open channel step-pool system lined with native vegetation and separated by rip rap rock riffles. With storms predicted to continue increasing due to climate change, management strategies to safely convey stormwater will also continue to become more critical. Scientifically informed RSC design guidance is limited and prevents more widespread application to protect these receiving waters and surrounding urban areas. In Knoxville, TN, modeling techniques were employed to optimize RSC pool dimensions and hydraulic performance. Preliminary results found that the number of pools did not impact hydraulic performance and instead pool/riffle geometry should be prioritized. The potential influence of site characteristics will also be identified and influence on performance will be evaluated. The main objectives of the project are to better optimize the RSC design thereby improving performance, stormwater quality, and increasing flood resilience.