As climate change brings more frequent flooding and storms to large swaths of the U.S., under-resourced communities tend to bear the brunt of their effects. This inequity is, in large part, due to a long history of discriminatory land use policies and practices that segregated and disinvested in Black and Brown communities, leaving them oftentimes both more vulnerable to flooding and less able to prepare for and bounce back from it. Smart growth approaches in land use policy can help build and support healthier, more prosperous, and more resilient communities.
How does flooding happen?
A flood is any event where water covers normally uncovered land, but there are several different causes and types of flooding. Most people are familiar with coastal flooding, where high tides combine with heavy rain and winds blowing more water onshore to inundate lower-lying coastal areas. River flooding, where heavy rain causes waterways to rise above their banks and inundate surrounding areas, may also be top-of-mind. However, other types of flooding can be just as dangerous. Storm surge, which is when the wind and waves associated with tropical storms and hurricanes move water toward coastal areas, is sometimes the most dangerous part of storms, as was seen in New Orleans with Hurricane Katrina. Inland flooding occurs when precipitation accumulates over an extended period or falls intensely in a short period of time. And flash floods, which can occur inland away from bodies of water or waterways, can occur so quickly that they can affect communities before they’re able to prepare.
How climate change increases the frequency and severity of floods
Whether from heavy rainfall, overtopped rivers, or storm surge, destructive floods across the U.S. and beyond are disrupting lives, washing away buildings, and leaving behind damage that is increasingly difficult to recover from as disaster response funding sources dry up. When considering the costs of repair and lost productivity in addition to damages, these flooding events can cost the economy up to half a trillion dollars annually. In the past five years alone, ten flooding events each caused more than a billion dollars in damages and were together responsible for 98 deaths. And these numbers don’t account for deaths due to flooding related to tropical storms and hurricanes.
Flooding has long been a threat to many communities, and the increased frequency and severity of flooding events is largely a result of our changing climate. As global temperatures rise, the atmosphere is able to hold a lot more moisture, which results in heavy rain. Tropical storms and hurricanes, fed by warmer temperatures, are becoming more dangerous and tend to move slower, dropping more water along the way.
Climate change, while responsible for unpredictable weather patterns that dump rain in bursts, also amplifies flooding by other means. Wildfires across the Western U.S., driven by dry conditions, harden soil and burn away trees and other plants. When rain returns, little of the water can be absorbed by the ground or vegetation, resulting in destructive flash floods like those seen in California. And all along the East Coast—from Boston to Washington to Miami—rising seas and water tables are driving more frequent and severe flooding events.
How to mitigate floods with smart growth
The built environment—guided by reformed land use policies—can play a role in equitably addressing the effects of climate change.
Zoning
Zoning regulations can reduce sprawl and impervious surface coverage, reducing flooding impacts. They can also more directly prepare communities for the impacts of climate change. Climate-informed zoning, as adopted by Norfolk, Virginia, uses zoning districts to redirect future development away from flood-prone areas. Other cities have undertaken similar efforts: in Charleston, South Carolina, zoning in higher-lying areas is designed to incentivize investment away from the floodplain; in Boston, zoning in flood-prone areas requires new development to include features aimed at reducing the impacts of future floods; and in New Orleans, requirements for green infrastructure that can mitigate floods are codified into the zoning ordinance. Additionally, because zoning reform can help break down geographic silos, zoning codes also have the potential to redress social and economic inequities and reduce greenhouse gas emissions.
Green infrastructure
Green infrastructure includes plant life that can absorb water, like bioswales, rain gardens, and green roofs. These can be strategically located to absorb water where it tends to collect; for asphalted roads, green infrastructure can be integrated into Complete Streets efforts. In Philadelphia, the Green City, Clean Waters initiative has resulted in almost three billion gallons of water being absorbed. Hoboken, New Jersey has incorporated flood mitigation strategies into infrastructure aimed at improving quality of life, including new parks, playgrounds, and street redesigns. These efforts, in part, contributed to the city’s ability to bounce back from Superstorm Sandy more quickly than others in the region.
Building interventions
Building codes and other policy tools aimed at boosting the resilience of specific buildings can also be a part of using land use to reduce the impacts of floods. Existing standards and rating systems can guide the development of these policies, reducing administrative burden for policymakers. FEMA already requires buildings in flood-prone areas, if constructed with funds from the agency, to be elevated above a certain level. This strategy, however, cannot be universally applied; elevating buildings is often expensive and sometimes directs floodwaters to neighboring properties. Alternative strategies include elevating a building’s mechanical systems (electricity, water, etc.) and establishing flood buyout programs that allow residents in flood-prone areas to move somewhere with less risk.
Transportation
When floods do hit, transportation systems must be prepared to serve as evacuation routes if people need to flee to safety. Federal funding is available for projects that prepare transportation infrastructure for weather events like flooding. The U.S. Department of Transportation’s PROTECT Grant program, for example, has provided $830 million in grants for projects that will boost the resilience of transportation infrastructure across the U.S., and the Environmental Protection Agency’s Community Change Grants program provides grants for communities to build more resilient transportation options.
With the increasing cost of housing entering the national spotlight and continued federal funding opportunities from the Bipartisan Infrastructure Law and Inflation Reduction Act available for projects boosting climate resilience, the U.S. is at a pivotal moment. The need for community-driven efforts to address climate injustices and to support healthy, prosperous, and resilient communities is clear—and policymakers must act to answer to it.