Because a warmer atmosphere holds and releases more water, climate scientists project an increase in the frequency and intensity of heavy precipitation events in coming decades. A recent study in the journal Nature found the track speed of hurricanes in the North Atlantic — due to warmer ocean temperatures — has slowed roughly 20%, exacerbating flood risks.
Coastal communities are vulnerable to routine inundation from rising sea levels and to storm surge (which reached over 15 feet with Florence and Michael). Inland areas are experiencing flash floods in smaller rivers and creeks, prolonged flooding along major rivers and urban flooding, where intense development speeds the flow of water across the landscape.
A recent study revealed that three times as many U.S. residents than previously thought are at risk of serious flooding. More than half the flood maps prepared by the Federal Emergency Management Agency (FEMA) have been found to be out-of-date or inaccurate, leaving many communities ill-prepared.
But the good news, Herlevich noted, is that "land trusts have an important role to play." Land trusts around the country are already working to protect the wetlands and vegetated floodplains that temper storm effects, to assess flood risks and to increase community resilience through planning and habitat restoration.
Intact ecosystems help slow the flow of floodwaters, buying time for soils to absorb rainwater. A Harris County Flood Control District study on property protected by the accredited Katy Prairie Conservancy in Houston, Texas, for example, found that prairie grasses absorb more than 8 inches of rainfall per hour compared to just half an inch for turf grass. "Prairie grasses are like a rainforest turned upside down," explains Mary Anne Piacentini, KPC's president and chief executive officer, "acting as a huge sponge with 12 to 18 feet of roots that can help absorb floodwaters and can also withstand drought." Locally, she says, "people are starting to get it," but there's not yet widespread recognition nationally of the vital role native vegetation plays in minimizing flood damage and maintaining water quality.
Vermont has particular challenges with controlling floods due to its narrow river valleys, notes Siobhan Smith, vice president for conservation and stewardship at the accredited Vermont Land Trust. Its staff teaches landowners about the importance of creating a "meander belt," a swath of undisturbed floodplain that lets the river channel move as needed. Since Hurricane Irene dumped 11 inches on the region in 2011, VLT has completed numerous "river corridor easements" to prevent shoreline armoring (the use of groins, jetties, offshore breakwaters, sea walls or other hardened beach structures on the shore to protect land from erosion).
At the accredited Lowcountry Land Trust in South Carolina, staff and volunteers are collaborating with a local Nature Conservancy scientist to gather data on ways to employ natural infrastructure that is less costly than seawalls in protecting vulnerable shorelines.
The initiative has been "really great for getting people engaged," according to LLT's director of science and stewardship, Lisa Shealy. More than 85 land trust volunteers have built two living shorelines from bagged oyster shells. The sites already show signs of significant marsh regeneration and will help scientists determine how best to deploy living shorelines in other settings. To encourage further use of green infrastructure, LLT is helping to facilitate efforts to streamline the state permitting process.
While most FEMA buyouts of "repetitive loss" properties currently happen through municipalities, land trusts could play a role helping communities break out of what has been dubbed the "flood, rebuild, repeat" cycle. Particularly in regions facing sea-level rise, municipalities urgently need help planning for inevitable change.
The accredited Eastern Shore Land Conservancy came to this realization early because it has always had "an expansive view of what the land trust could or should be in the community," explains Brian Ambrette, ESLC's director of strategic initiatives. It first focused its annual planning conference on sea-level rise in 2013, drawing a record 250 people. ESLC works in "a very red region of a blue state," Ambrette notes, but has had success focusing community leaders on adaptation because people see "an existential threat in sea-level rise" and have already observed increased flooding and shoreline erosion.
Farther south in the Chesapeake Bay, a pilot project is underway that could offer hope to "communities where the infrastructure and tax base is built on soggy land," suggests Mary-Carson Stiff, director of policy at the nonprofit Wetlands Watch and a board member of the new Living River Restoration Trust. She is working with two Virginia cities, Chesapeake and Norfolk, to provide enhanced financial incentives for people facing repeated flooding to voluntarily relocate.
Given that local governments can't stretch FEMA grants further, and private landowners are finding it hard to sell vulnerable properties, there's a clear need for new revenue streams. In Norfolk, Stiff explains, "A resilience point-based zoning ordinance now offers developers credit for specific actions that reduce risk" (such as more sustainable construction or funding land conservation linked to a shoreline retreat strategy).
Stiff calls it a "Transfer of Risk" program (akin to Transfer of Development Rights programs), in which LRRT will receive checks for land conservation written by developers earning needed resilience points, and those funds will cover costs associated with a "rolling conservation easement" voluntarily placed on a high-flood-risk property. Property owners have an incentive to participate as they can benefit from favorable state tax credits, federal tax deductions and reduced property taxes.