A practitioner-friendly approach to quantifying the hydrologic benefits of city-scale distributed green stormwater...

The practice of green stormwater infrastructure (GI) is rapidly advancing. However, there remain complex challenges to upscaling its practice from localized installations to city-scale distributed systems. The purpose of this work is to address technical challenges associated with upscaling GI by demonstrating a practitioner-friendly modeling approach for quantifying hydrologic benefits that is sensitive to GI placement within a cityscape and actionable with the common tools of practice. The approach is demonstrated for an urban coastal community in Georgia, USA, with a distributed hydrodynamic model (StormWise) that simulates multiple flood hazards, the services of conventional stormwater infrastructure, and expansions of the urban canopy cover (UCC) along roadways and in residential areas. Hydrologic benefits are quantified at the site and city spatial scales during design storms (4-100% AEP), and results suggest approximately linear relationships, for example, 0.17-0.54% reductions in runoff for every 1% of land use converted to UCC and 0.98-1.34% reductions in runoff for every 1% reduction in aggregate imperviousness. In addition, the results suggest the potential for city-wide reductions in runoff (up to 54%), reductions in the service demand on conventional infrastructure (up to 57%), and reductions in flood depths on buildings (up to 33%), as well as the greatest efficiency on a per-km² basis from UCC expansion along roadways. Despite the challenges of distributed modeling, the proposed approach is tailored to the types of geospatial datasets available to practitioners and demonstrates an efficient, repeatable approach for quantifying GI services with the common tools of practice.