An uncertain future calls for flexible flood solutions: How can non-structural solutions reduce your flood risk?August 31, 2022
By Rebecca Verity – Senior Climate Adaptation Scientist
Flood risk management in North America has traditionally relied on large, physical structures to manage and contain floods. Levees, dams, and sea walls have been relied on for centuries to keep our communities safe. But, as rainstorms intensify, hurricanes strengthen, and extreme weather become commonplace, those traditional structural solutions are being challenged by faster, deeper, bigger floods. In a changing world, we must ask: Are solutions designed for the last century still the best choice for the next? To answer that question, we must define flood risk management goals, which starts with defining risk. Let’s look closely at this definition to challenge our traditional reliance on structural solutions, and find new, flexible, resilient solutions.
The U.S. Army Corps of Engineers (USACE) defines flood risk as the product of (1) the probability of a flood happening and (2) the consequences if the flood occurs, thus:
Risk = Probability × Consequence
USACE has historically managed flood risk by reducing probability: the likelihood that a flood will reach a community or asset by channeling and constraining the flood flow. We manage probability by physically constraining water. Over the last decade, USACE has been shifting significantly towards nonstructural solutions. Rather than restricting where flood waters go, these solutions reduce the harm done by flood waters. We achieve this by flood proofing or elevating individual buildings, improving flood warning systems, or moving people and infrastructure out of repeat flood zones. In some regions, these solutions pencil out economically. Elevating each home in a neighborhood may be an order of magnitude less costly than building a ring levee around the neighborhood, for instance. Non-structural solutions bring additional benefits: Without a levee, the ecological health of a river valley may improve and the community alongside it gets access to recreation, shade, cooling, and beauty that might otherwise be walled off. The addition of nature-based flood management features, from wetland restoration to horizontal or “ecotone” vegetated levees, can further increase these community benefits, even while mitigating a portion of the flood probability side of the risk equation.
Across the country, large-scale USACE flood risk management projects are now moving forward with primarily nonstructural features. This reflects a significant shift in the types of approaches USACE is now considering in support of flood risk management solutions, and it opens the door for flood management agencies of all sizes to follow suit. Now is the time to explore a much wider portfolio of options than have traditionally been available.
FEMA is also looking at flood management in a new light; investing significantly in disaster prevention through funding projects that will increase communities’ climate resilience – including flood resilience. Over the past two years, FEMA has given out over $1.5 billion in grants through their Building Resilient Infrastructure and Communities (BRIC) program. BRIC funds projects to build climate resilience, and next year the program will provide an additional $2 billion in grants. In that competitive grant process, additional points are awarded to projects which specifically focus on nature-based solutions to reduce climate risks.
Nonstructural and nature-based flood-risk management solutions bring flexibility, cost reductions, community and environmental benefits, and are adaptive to our changing climate conditions. To better understand the national shifts in flood management directions, and to position your community for the unprecedented opportunities in flood resilient grant funding, contact me.
Rebecca Verity, along with Lea Adams (USACE), Andy MacInnes (USACE), and Eileen Takata (USACE), will present on non-structural flooding solutions at the Floodplain Management Association (FMA) annual conference in Sacramento on Tuesday, September 6. Learn more about the FMA Conference.