Stormwater Management in Extreme Events

Dr. Bill Hunt’s talk at the Museum of Natural Sciences in Raleigh on August 9th focused on the historic flooding hurricanes NC has seen in recent years, and what that means for stormwater management. We all remember when 6 feet of water stood on I-40, making Wilmington was an island and closing 3200 roads statewide. Our highways were (in theory) designed for the 1/500 year storm event, but Florence was a 1/2000 year event in Wilmington.

An NCDOT staff member in the audience shared that they worked with NC Division of Emergency Management and the Navy (yes, the Navy) to ensure that Wilmington had adequate supplies. Looking forward, DOT is working with the National Weather Service and others to stress-test our highway system, as well as learning from Louisiana’s experience during Hurricane Katrina to study bridge span vulnerability (many bridges went out during Katrina due to wave action.)

So what does this mean for stormwater management using green infrastructure? Stormwater managers know that green infrastructure has been designed to effectively treat moderate-sized rain events. How can stormwater BMPs / SCMs safely convey or pass larger storms, while still meeting their treatment goals? Dr. Hunt said that we will probably need to design our SCMs to be a bit bigger and made out of more durable materials. Thinking more broadly about green infrastructure, he also emphasized the need for preserving lands that routinely floods as public amenities. Designing parks, ballfields, or urban agriculture areas that can survive being submerged and somewhat battered in storms will allow us to “live with water” better.

Dr. Hunt and others in the audience also emphasized the importance of breaking down our institutional and subject matter silos. Stormwater, transportation, and emergency managers–and developers–can learn from one another about how best to manage risk and maintain the resilience of the systems where we work, play and live.

How are you designing your SCMs and planning land use for extreme events? How are your partnerships with other managers evolving? Leave a comment below about what’s helping you solve these challenges we all face.

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