Critical Thinking: Flood Mitigation

March 3, 2017  | By Shoal Creek Conservancy

This blog post was written by Andy Sobchak. To learn more about the author, please visit this site.

This morning on the homepage of The New York Times, David Dunlap writes about a 7-foot-tall deployable flood fence designed to protect the waterfront Empire Stores commercial district in Brooklyn.

“Deployable” means the fence is not permanent. When significant storms like 2012’s Hurricane Sandy rumble up the eastern seaboard, city maintenance crews transport the fence material from a nearby warehouse and erect all 1,100 feet of the defense, a process requiring about half a day. After the storm has passed and floodwaters receded, the fence comes down and returns to storage.

Dunlap’s article is one in a series The New York Times is developing, examining resiliency designs throughout New York. Articles in January and February discussed the trend of residential sky scrapers – new and old – relocating critical infrastructure like boilers and generators to higher floors or the roof and out of basements, in some cases taking over valuable penthouse space. In doing so, buildings remain operational during a flood, especially if the water gets past initial defenses like the Empire Stores’ fence.

Flood mitigation is a hot topic in many cities around the world not only because of the unknowns regarding each city’s ‘next big storm,’ but because resiliency plans vary so widely. The Shoal Creek Conservancy released City + Water this week, a showcase surveying innovative approaches to stormwater management and and urban flood mitigation. Resiliency planning in one city does not necessarily translate well to the next, which means examination of case studies in City + Water or from The New York Times requires some critical thinking: How do these lessons apply here in Austin?

Photo: BIG

New York’s ambitious Dryline project – a 13-mile-long swath of parkland, trails, public space, skate ramps, deployable flood barriers and more, all sewn together to provide a consistent level of flood protection – is proposed to wrap around the lower end of Manhattan, keeping safe a $500 billion business district and arguably the world’s most important economic engine. The Dryline inspires consideration for how development of an elevated Shoal Creek Trail could help contain the creek’s floodwaters to the its green corridor.

Photo: Sand Hill Property Company

The world’s largest green roof may never be constructed at The Hills at Vallco in Cupertino, California, but the mall redevelopment concept sparks wonder about low-impact development (LID) and retrofit resiliency opportunities at Shoal Creek’s own Highland Mall. Sites located in the upper portions of a watershed can often be critical tools in downstream flood mitigation.

Photo: Tredje Natur

The Sankt Kjelds Climate District, a pilot area for resiliency planning in Copenhagen, was able to convert 20% of the paved surfaces in their rights-of-way (e.g., roads, sidewalks, parking, boulevards, etc.) into impervious areas which absorb stormwater without compromising traffic or parking capacity. With traffic and parking already a sensitive subject in Austin, is this an option for our watershed?

With tongue in cheek, Andrew Grant, lead designer for Singapore’s Supertree grove described the ideation of his award-winning project as “simple”: His client, Singapore’s National Parks board wanted the most amazing tropical gardens in the world and the city’s best outdoor recreation space. Grant’s team mixed in cutting-edge environmental technologies and contemporary thinking about how to manage natural resources. “On a plate,” Grant said, “this is what Singapore is all about.”

What is Austin all about?

With flood mitigation and resiliency planning potentially having a great impact on the way the Shoal Creek watershed looks, feels and functions, it’s critical to consider what we want as a community, and as a city.

Read all 10 City + Water case studies here, and join the City of Austin-Watershed Department on March 9 (6:00pm at Cirrus Logic – 700 West Avenue) for the first open house of the Shoal Creek Flood Mitigation Study. Learn, have your say and, as a community, let’s discuss what Austin is “all about.”

Photo: A “flip-up” hydraulic barrier as pictured provides similar flood protection as the “deployable” flood fence used at Empire Stores. These barriers are permanent and remain flush with grade when not activated. Wakefield, United Kingdom. © Flood Control International