BMPs & Resiliency

       Reported by Dave Mason, CDM Smith and Cory Rayburn, City of Johns Creek, GA


In the face of escalating climate change and the increasing frequency and intensity of extreme weather events, the imperative to fortify urban environments against the impacts of stormwater runoff has never been more critical. Stormwater Best Management Practices (BMPs) emerge as indispensable tools in fostering urban resilience, serving as a frontline defense mechanism to mitigate the adverse effects of intense precipitation, flooding, and water pollution. Both the implementation of new BMPs and the strategic retrofitting of existing infrastructure are crucial components in this battle for environmental sustainability. This article highlights the pivotal role of both new and retrofitted stormwater BMPs in bolstering urban resilience, shedding light on their multifaceted contributions to the protection of communities in the face of a changing climate.

Many opportunities exist to apply BMPs to enhance stormwater capture and treatment, including areas that may not currently receive treatment. Common examples of retrofit opportunities include: 1) near existing stormwater outfalls, 2) within the existing conveyance system, 3) adjacent to large parking lots, 4) green street retrofits, and 5) on-site LID retrofits. While it may be difficult to get private development to retrofit their property, many local governments have performed studies to identify improvements on a regional scale within public property or the right-of-way. States in the southeast such as Tennessee include an optional fee-in-lieu program in the MS4 permit to incentivize local governments to build regional BMPs that serve private development.

The pursuit of resiliency within existing stormwater systems can also involve the conversion and/or enhancement of existing BMPs. Numerous communities grapple with aging, legacy BMPs like dry ponds and wet ponds, originally designed under outdated standards or requirements, providing limited flood and water quality benefits. In response, the strategic upgrading of these facilities emerges as a popular and cost-effective alternative to constructing entirely new infrastructure. Such enhancements have the potential to increase treatment volume, prevent short circuiting, extend flow path or hydraulic residence time, and incorporate internal design features to elevate overall efficacy in flood and/or pollutant reduction. This approach not only addresses the challenges posed by outdated stormwater infrastructure but also exemplifies a practical means of fortifying resilience within existing systems.

Another area where local governments can better take advantage of resiliency building is within our planned roadway projects. These transportation infrastructure improvements are historically well funded and tend to be exempt from the same stormwater standards imposed on private development. With the overall success of underground detention systems over the past twenty years, there is an opportunity to strategically place these linear BMPs along the roadway to build resilience, volume, and attenuation into these more traditional conveyance-focused projects. There have also been some great LID successes in the right-of-way, but it has yet to become the mainstream approach for transportation engineers.

This article underscores the pivotal role of both new and retrofitted stormwater BMPs in bolstering urban resilience, emphasizing their multifaceted contributions to community protection amidst a changing climate. Opportunities abound for implementing BMPs, from strategic retrofits near stormwater outfalls to green street retrofits, showcasing their adaptability across diverse urban landscapes. By strategically upgrading aging infrastructure and integrating BMPs into planned projects, we can systematically build resilience, block by block, creating a more sustainable future for our communities.