A sweeping federal assessment of the increasing risks from storm-driven flooding up and down the nation’s southeast Atlantic coast ranks Florida among the most vulnerable areas, with the economic tally in the state accounting for nearly 90 percent of the potential damage across six states, Puerto Rico and the U.S. Virgin Islands.
In a final briefing on the four-year study by the U.S. Army Corps of Engineers this week, Corps officials listed more than 200 recommendations to address the threats.
In Florida, they are asking Congress to authorize the design and construction on massive projects that fortify the coasts along Biscayne Bay and in Broward County, the Florida Keys and Key Biscayne. With the exception of Broward, which they say could entail more complicated coordination, they want that work to begin in less than five years.
The sprawling report, divided into appendices on each state and territory, also provides maps and data assessing the risks and the costs of flood threats made worse by a warming planet.
“This really allowed us to look at potentially high-risk places and stack and compare places by state to see which incorporated municipalities or towns or cities experienced a higher dollar damage,” said Trevor Lancaster, a Corps geographer. The survey look at costs due to flooding from storms or sea rise, he explained.
In Florida, they found that with three feet of sea rise, annual damages from storm surge alone could amount to $24 billion - 12 times higher than South Carolina, the next closest state.
Among the South Florida projects recommended and unveiled three years ago was a back bay plan for Biscayne Bay. The work would protect neighborhoods and cities that line their shores with flood walls or gates across coastal rivers, as well as other structures, and is expected to cost $4.6 billion.
The towering walls along the scenic bay and other hard infrastructure drew sharp criticism from Miami-Dade County officials and environmentalists, who want to include features like mangroves and seagrass meadows. In addition to buffering punishing waves from storm surge, these more natural defenses could also provide desperately needed wildlife habitat for Miami-Dade’s urban shoreline and help improve water quality.
If local communities object to such plans, the Corps allows them to come up with alternative proposals. A year ago, Miami-Dade asked for an extension, which was forwarded to the Assistant Secretary of the Army for approval. As of April, Corps officials said it was still under review. When asked about the plan, Miami-Dade resilience chief Jim Murley said that he expects to make an announcement this week.
In addition to the back bay plan, Corps officials say it’s also time to take a closer look at the regional flood control system that stretches across South Florida and is now nearly 75 years old. The South Florida Water Management District is in the midst of implementing a series of coastal projects aimed at dealing with rising sea levels driven by climate change, including saltwater intrusion from outdated coastal pumps. But Corps officials say the work “may not evaluate comprehensive solutions to address increased risk inland.”
In its analysis of increasing risk that identified about 490 locations statewide, Corps analysts found sea rise could have a much greater impact far inland, in places like Homestead. Corps officials also noted the growing risk, as South Florida’s population swells and development deepens in areas likely to flood.
“Increased population and development, without planning for resilience and adaptation to sea level rise, will further increase the substantial risk,” Corps officials noted in their report.
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