Mary Caperton Morton, Science News, August 6, 2019
The five U.S. cities most at risk from coastal flooding
have begun to make plans for adapting to rising sea levels. Some are further along than others. Here’s where their flood resilience efforts stand:
Florida’s flooding risk comes not just from storms and high tides but also from water seeping up through the porous limestonethat underlies much of the state. After 2017’s Hurricane Irma caused more than $50 billion in damage, Miami residents voted in favor of a new tax to fund coastal flooding resilience projects across the city. The first project, in the city’s low-lying Fair Isle neighborhood, broke ground in March and will construct a drainage collection system and raise roadways.
New York City
In 2012, Hurricane Sandy hit New York City with a 3.4-meter storm tide, causing over $19 billion in damage. Although there are now several programs to guide rebuilding and resiliency efforts, few adaptation projects have come to fruition, says Robert Freudenberg, an environmental planner with the Regional Plan Association in New York City. In March, the New York City Panel on Climate Change released a report and new flooding maps. In May, the city’s Office of Emergency Management began installing sandbags around lower Manhattan as a temporary measure to protect the waterfront while more permanent solutions are considered.
Louisiana is one of the most flood-prone states, thanks to a combination of rising sea level, sinking landmass and the floodprone natures of the Mississippi and Atchafalaya rivers. Sinking in particular is a major problem as the river sediments that once replenished coastal land are blocked by levees, unable to refill riverbanks and estuaries. Since 1930, nearly 5,000 square kilometers of land have been inundated with water, with 10,000 square kilometers imperiled in the next 50 years. This loss of protective marshland leaves New Orleans more exposed to Gulf storms and flooding. In May, Louisiana released a $40 billion plan called LA SAFE to build needed levees, restore shorelines and, if necessary, relocate entire communities at risk from flooding. The first LA SAFE projects are slated for completion in 2022.
Like much of southern Florida, the Tampa Bay region already sees regular flooding during high tides and storms. Since 1952, sea levels in Tampa Bay are up by about 18 centimeters. In April, Tampa’s Climate Science Advisory Panel recommended that the city begin preparing for seas to rise an extra 30 to 76 centimeters by 2050 and 60 to 260 centimeters by 2100. Those ranges are NOAA’s predictions for sea level rise, depending on different climate change scenarios. A timeline for starting adaptation projects hasn’t been announced.
With neighborhood-level projections for future sea level rise in hand, the city of Boston has district-level projects completed for East Boston, Charlestown and South Boston. A deployable flood wall is being installed along the East Boston Greenway and a section of Main Street in Charlestown is being elevated to protect the adjacent neighborhood. In several areas, including around South Boston and the Seaport, concrete is being removed and replaced by floodable parks and green space. Mayor Martin Walsh has pledged 10 percent of the city’s $3.49 billion capital budget in 2020 for such resiliency projects.
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