A loss of natural buffer zones that help protect areas from the impacts of storm surge and sea level rise, combined with changes below the surface of waterways from urbanization, are increasing coastal cities' vulnerability.
What's happening?
The combination of human-caused changes to estuaries and rising water levels on our overheating planet is raising the risk of damage as tidal flooding increases and storm surges worsen. This year, Hurricanes Milton and Helene showed how storm surges can cause widespread devastation.
Estuaries, the bodies of water and surrounding wetlands where rivers meet the sea, have thrived for centuries and provided habitats for many species of birds, fish, mammals, and other wildlife. However, the habitats in the estuaries of New York Harbor, San Francisco Bay, and Miami's Biscayne Bay are now 80% to 90% built over, according to a report from The Conversation.
Research published in the Annual Review of Marine Science in 2020 noted that, since the 19th century, the depth of shipping channels has more than doubled due to large-scale engineering and dredging projects. Newer, deeper channels allow the water to more easily enter and exit the estuaries as tides rise and storms strike, as detailed in The Conversation.
Nuisance flooding from the impacts of dredging is visible in several cities during daily tides. Nuisance Flooding is defined by Science Advances as "minor, nondestructive flooding that causes substantial, accumulating socioeconomic impacts to coastal communities." The research reveals sea-level rise is the main driver for the increase in nuisance floods in the United States that have been observed.
Why are these human-caused changes to the environment important?
The changes to estuaries from urbanization in several places along our country's coastline, like southeast Florida, southern Louisiana, and New York City, are expected to raise water levels, which has the potential to cause more damage for regions unprotected from hurricane storm surge.
"These costs have gone largely unnoticed, since changes have occurred gradually over the past 150 years," according to The Conversation. "But as sea-level rise and turbo-charged storms increase flooding frequency and severity, the problem is becoming more visible"
What's being done about the rising vulnerability of coastal cities?
Per the report, The U.S. Army Corps of Engineers suggested surge barriers as a way to deal with rising coastal flood risk. Last year, it recommended barriers in at least 11 estuaries in the United States that would "partially block estuary-ocean exchange with infrastructure across an estuary or its inlet and include gated areas that are closed only during flood events."
Massachusetts recently announced grants of nearly $4 million to support river and wetland projects in the state. This is a proactive effort to make the state's coastline more resilient by restoring ecosystems.
Turning the tide on relying on dirty energy sources in favor of renewable options is essential to lowering the rising risks our coastal cities face. Purchasing an EV for your next vehicle, installing solar panels on your home, and making your home a smart home are all ways to cut down on harmful carbon pollution.
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