Florida’s Beaches Have a Problem, and Hurricane Matthew Ain’t Helping
Hurricane Matthew is already a tragedy. It killed hundreds battering through the Caribbean, and knocked out power, forced evacuations, and flooded beaches as it scoured the Florida coastline. But thinking long-term, the storm is a punctuation mark in the creeping erosion narrative playing out on many southeastern shorelines.
Erosion is nothing new. Shorelines experience seasonal ebbing from winter, and typically regrow in the summer. Longer term, things like development—and way longer term, sea level rise—cause a more gradual coastal deterioration. Big storms, like Hurricane Matthew, have the potential to alter, or hasten those other erosional patterns, by reshaping the shoreline, devouring dunes, or demolishing human-made fortifications.
Beaches are money. Tourism contributes $67 billion to the Florida’s economy, and not all those people are headed to Disney World. Besides bronzin’ and beach volleyball, sandy shorelines also support ecosystems. And yet, nearly half of Florida’s 825 miles of sandy shoreline are state-designated critical erosion areas. “In some cases, the extreme events are why we have long term erosion,” says Spencer Rogers, coastal construction and erosion expert with Sea Grant North Carolina.
Imagine a beach on a nice, normal, summer day. The flat part where you lay your towel is called the berm. Behind you is a barrier of dunes, covered in grasses, succulents, or other plants specialized for the super-sandy substrate. Between you and the ocean is a sloping, wave-lapped area called the beachface.
Now, let your imagination return you to that same beach in winter. Your beloved berm is gone, pulled out to sea by regular storms. If it is a particularly vicious winter, the waves might have chipped the dune face into a scarp. This is seasonal erosion, and not usually a big deal, because summer comes along, the storms abate, and wind patterns restore the berm. And so it’s not so much erosion as it is a seasonal fluctuation, in which hurricanes play their own role. “Hurricane passage with high waves and surges will cause dune erosion, but a lot is temporary,” says Rogers.
Not always. Big storms like Matthew can pull sand into deep water. So deep, that the normal waves and tides that come after the hurricane won’t be strong enough to drag the stuff back up onto the beach. But, because shore erosion is a long game, scientists won’t know where (or whether) Matthew hastened long term erosion. More obvious are the effects on low shorelines, where Matthew could push sand inland, past the beach, into coastal shrubbery, marshlands, or communities.
Not helping matters is the fact that long-term erosion doesn’t just come from hurricanes. People build things like seawalls and other hard fortifications to protect their houses and communities from storm surge. If those seawall don’t allow normal waves and tidal action to deposit sand into dunes, wave action will eventually wash the beach away. “You can get hurricane protection from a big enough seawall, but long-term erosion will cause the beach to disappear,” says Rogers.
Speaking of human contributions to erosion: sea level rise. This is a slow, slow process. Over the past century, the worldwide sea level has only risen an average of 8 inches. How this slow creep plays out on individual beaches depends on a lot of different factors. But generally, in places not rebounding from being held down by glaciers during the last ice age (seriously, it’s a thing), the normal wave action chips at the sand a little deeper. Maybe that’s only 1/10th of an inch a year. But fast forward 100 years, 200 years, to the altered shorelines predicted by 2˚ Celsius or more of global warming. Add in the stronger storms that speed things up. “What happens in a dune system is the beach just migrates farther inland, redistributing the sand from lower beach into inner beach,” says Rogers. Assuming, of course the inland isn’t paved and built upon. In that case, the beaches get washed away. Possibly the houses, roads, and businesses, too.
Dunes save beaches from eroding away. When a storm comes, they stop the surge from pushing too far inland. And when the foul weather abates, smaller waves and weaker winds restore the berms. “The bigger the sand supply and dunes, bigger protection you have and more severe storm you can tolerate,” says Rogers.
Many coastal areas have beach nourishment projects to maintain the dunes. This is big work, typically involving sand dredged from offshore, bulldozed into tidy dunes, and seeded with plant life to make sure the mounds don’t wash away. This work is expensive, and not always something politicians are willing to pay for in coastal stretches with low property value.
But do you know what’s also expensive? Beach erosion forcing people to abandon their communities. The storm, as they say, is a-coming.
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