Hydrologic Performance of a Regenerative Stormwater Conveyance: A Case Study, Powell, TN

Abstract Submission: 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, bypassing 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 a green infrastructure practice reported 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 storm intensity predicted to continue increasing due to climate change, management strategies to safely convey stormwater will become even more critical. As an emerging stormwater control measure, studies documenting RSC performance under variable site characteristics are limited, preventing more widespread application. In Powell, TN, an RSC was designed and constructed to manage erosive flows in a local park. The main objective of the project was to characterize the conditions influencing the hydrologic performance of RSCs, thereby leading to improved designs. To illustrate how the RSC design process can be improved, the standard design methods were supplemented by advanced hydraulic modeling. Overall, this study showed how modeling tools can be incorporated into existing RSC design guidance and the degree of hydrologic performance with response to environmental variables, such as antecedent dry period and seasonality.

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