The flooding that hit Louisiana last week affected hundreds of thousands of people over 1,000 square miles. The intense storm claimed 13 lives, and some 30,000 needed to be rescued. Over 60,000 homes have been destroyed, and 100,000 have registered for Federal Emergency Management Agency (FEMA) assistance so far. According to the agency, the Louisiana flooding was a 500-year flood event, meaning there was just a 0.2 percent chance of this happening this year. However, this is the 8th 500-year flood event since May, 2015, which beg the questions: With climate change, are flood risk estimates now completely unreliable? And if super-storms are the new normal, what can communities do to build back smarter and make themselves more resilient to the next unexpected, disruptive event?
Wes Michaels, ASLA, a partner with Spackman, Mossop and Michaels, a Louisiana-based landscape architecture firm, said: “More rain fell in 4 days in Louisiana than the last 4 years in Los Angeles. A lot of places considered low-risk areas for flooding got a substantial amount of water, so it’s not just about people living in low-lying, flood-prone areas. These super-floods are unpredictable; they flood areas many people consider high and dry.”
Super-storms, while unpredictable, are becoming more common with global warming. As David Titley, a meteorology professor and the director of the Center for Solutions to Weather and Climate Risk at Penn State University, told Fast Company: “Warm air holds more water vapor than cold air, and we’re warming up both the air temperature and we’re warming up the oceans. Welcome to the future.”
The Washington Post editorial board in part blames FEMA’s out-of-date flood maps, “which determine who needs to buy government-sponsored flood insurance,” for the extensive damage. These maps “did not assess large portions of the area hit last week to be at high risk.” In reality, this means many of those hit by the storm will “not be able to call on an insurance policy.” The government only “presses people who live in so-called 100-year flood zones, areas that annually face a 1 percent chance of being flooded, to purchase government-backed flood insurance.”
According to Insurance Commissioner Jim Donelon, only 12 percent of homes in Baton Rouge and only 14 percent in Lafayette had flood insurance. As Elizabeth “Boo” Thomas, FASLA, President and CEO, Center for Planning Excellence in Baton Rouge, noted in an appeal posted to ASLA’s LAND, “though the floods affected people of all incomes, early indications show that a majority of victims are working-class or low-income individuals and families.” Many of those hit by the flooding couldn’t afford flood insurance, which is expensive, or didn’t expect they needed it. If a homeowner is insured, FEMA will pay out up to $250,000 in funds to rebuild. Thomas estimates the estimated value of the affected homes is around $5.7 billion.
FEMA only updates its maps each decade or so. But climate change and sprawl, which creates more impervious surfaces prone to flooding, are more rapidly changing the map of flood risk, particularly for coastal areas. Insurance premiums need to be tied to up-to-date flood risk, with higher premiums for higher risk zones.
According to Wired, communities now need “predictive flood maps: projections of flood risk based on modeling. Right now, pretty much all flood insurance comes from FEMA, which, again, updates its maps infrequently and also allows residents to comment and push back on the boundaries, effectively letting them determine their own flood risk. Insurance companies, which might have the capital to invest in models that incorporate climate change, have largely stayed out of the business since the 1920s—partly because it’s too risky, partly because government-subsidized rates are too low for private companies to compete with.”
But some firms, like Risk Management Solutions, are now developing their own flood risk modelling tools, because real-time modelling “could lead to better estimates of risk in certain places, which would allow companies to price policies accordingly and residents to really understand how risky their locations are. And as FEMA enacts some much-needed reforms (like phasing out government subsidies, for one), it may become easier for insurance companies to offer up flood policies, too.” Expanding the areas of people who are encouraged to buy into flood insurance could also help. Wired writes “if the insurance pool included people from 500-year floodplains, the risk would spread out more thinly,” reducing rates.
Beyond making the flood risk insurance system more responsive to a rapidly-changing climate, communities at higher risk of floods also need to rethink the status quo. Thomas believes that “smart, community-driven planning will play a lead role in rebuilding communities designed to thrive against a changing environmental context.”
And Michaels called for that planning effort to include a deeper analysis of the implications of car-based patterns of development. “As landscape architects, we need to be more involved in the design of infrastructure. Some of the unpredictability in flooding patterns comes from the storm itself, but some of it comes from how we design our interstates, roads, dams, bridges, canals and their related drainage systems. We need to think about how infrastructure fits into the larger landscape systems. Roads in particular, being long, linear systems, can drastically change how high intensity flood waters move across the landscape. There is an image in the news of a highway median wall backing up water on one side of the interstate near Walker, Louisiana. This wall may or may not have not caused flooding in other adjacent areas, but it certainly altered the flow of the water. These large infrastructural systems are pushing water around in ways that make the flooding less predictable, which makes planning for disasters more difficult. Our infrastructure needs to be designed to be porous to the flow of water (and species) across the landscape, and adaptable to the landscape at a much larger scale.”
He added that landscapes in high flood risk areas also need to be made more resilient: “Landscape architects should be leading the call to design our landscapes to be resilient to flood and disaster. The amount of energy, resources, and effort that will go into ‘re-landscaping’ Baton Rouge is staggering. Not to mention the carbon footprint of all the dying vegetation that must be cleaned up. We can no longer afford to see these disasters as outlying events, and go back to business as usual after the flood waters recede. We need to design landscapes that can be cleaned up with minimal effort after flooding and will adapt to changing soil and climactic conditions over the coming decades. We need to plant resilient perennials that can be chopped to the ground and come back to life. We need to plant trees that can resist flooding, and use soil technologies that allow trees to be healthy in the first place so they can survive stress.”
Michaels concluded: “I don’t think we can design systems that will prevent flooding in a 1,000 year storm. But we can think about the larger implications of our systems and how they will function in super storms at the landscape scale. And we can be smarter about how we design our landscapes and cities, so we can recover from these events more quickly and with less use of limited resources.”