Beaches Under Assault: Storms and Sea Level Rise

by Christina Holland and Rich Young

Everyone thought Rosa and Clara were sisters. The look-alike teenaged cousins were as close as close can come, and they did everything together. Considering they grew up in Key West, Florida, "everything" usually occurred on the beach. For them, the word "beach" conjures up all sorts of vivid images: towering sand castles, rainbow-colored beach balls, explorations in busy tidal pools, funky-looking snail shells, and family volleyball games. Their list is as endless as the grains of sand in front of their side-by-side childhood homes.

About two years ago, Rosa and her parents left Key West to manage a beachfront hotel in Biloxi, Mississippi. She and Clara keep in touch on email. Rosa's always loved the beach of course, but realizing that her family's livelihood now depended on it made her want to know more about it - beyond the childhood memories.

Clara, who still lives with her family in Key West, always admired the beach too. It's like a work of art, she'd say. She still loves to watch every wave mold the beach like the hand of a potter, and every season leave its signature on its dynamic outline. And like Rosa, she too always wants to know more about it. Through her classes at Key West Middle School and some on-line surfing of her own, Clara's beginning to understand the science behind this natural wonder, and naturally, she and Rosa talk about the beach all the time.

Hurricane Georges recently paid Clara and Rosa a visit, and the two learned more than they'd ever hoped about beach dynamics. In a minute, you'll read their thoughts about the hurricane in the email letters they sent back and forth after the storm ran its course. Hurricane Georges hit Key West first, where Clara lives. After sucking up lots of moisture over the Gulf of Mexico, Georges eventually made his way up to Biloxi - Rosa's new stomping grounds - which buffers the Gulf's northern edge.

Rosa and Clara are fictional characters, but their stories echo those of coastal residents who have lived through Mother Nature's mood swings, and who learn first-hand how dynamic the life of a beach can be.

 
 
 
 
 

date: Saturday, September 26, 1998  from : Clara_Summers@surf.Key_West.net  to:Rosa@OceanViewHotel.Biloxi.net  Hi Rosa, It's been kind of crazy around here! Hurricane Georges hit yesterday morning. School was closed, so that was pretty cool, and before I forget, mom says to tell you guys that we're all safe here. No need to worry.  When Georges hit Puerto Rico, they kept saying on TV that it was a category 4 storm. I didn't know what that meant, so I looked at the National Hurricane Center's web page (http://www.nhc.noaa.gov). Category 4 is pretty bad (but category 5 is the worst). The wind was blowing between 131 and 155 miles per hour, and they said storms that bad only hit the eastern U.S. every 5 or 6 years - the last one in south Florida was Andrew in 1992. Luckily, Georges was down to a category 2 by the time he hit here (96-110 miles per hour).  Do you remember Hurricane Andrew? You and me, our parents, Grandma and Gramps - all crammed inside together for hours. I was only seven then, so I was scared -a little anyway :). And the power was out for weeks. But I guess people here learned something from Andrew; everybody was much better prepared for Georges.  As soon as things calm down, I bet my earth science class will have a field trip to check out the beach damage from Georges. That'll be fun. They said on the news that Georges will hit the Gulf of Mexico coast tomorrow or Monday. Looks like it's your turn now! Write and tell me what happens in Mississippi. -Clara

 
 

date: Tuesday, September 29, 1998 from: Rosa@OceanViewHotel.Biloxi.net  to : Clara_Summers@surf.Key_West.net  Hey Clara,  Wow, Georges came straight for us! Landfall was early yesterday morning, and people throughout coastal Louisiana, Mississippi, and Alabama are feeling the effects. Mom and Dad and I are safe, although I think I drove Mom a little nuts while we had to stay inside.  I don't know what we're going to do though. The hotel buildings are badly damaged, and even worse, half the beach got washed away in the storm surge!  Do you remember the Isles Dernieres barrier islands? We picnicked there when you came up last summer. Well, the islands are constantly eroding. I remember my teacher telling us how, even before Andrew, erosion was so bad the islands would be underwater by the year 2020. Then Andrew came and swiped like two-thirds of the beach sand, so the islands will be gone by the year 2000. I hate to think what Georges has probably done. I guess we'll have to find a new picnic spot! Love, Rosa  -Clara

 
 

date: Tuesday, September 29, 1998  from : Clara_Summers@surf.Key_West.net  to: Rosa@OceanViewHotel.Biloxi.net  Dear Rosa,  I'm glad you're safe, anyway. The dust is settling around here. We've been hearing a lot in school about Georges' less obvious effects. Like the corals. A bunch of the corals in the Florida reefs broke right off. Some of them grow less than an inch a year, so it will take several years for them to recover. The SCUBA diving won't be the same, and that'll hurt tourism and stuff.  On the other hand, a lot of the beaches got covered by these thick weed mats. The people who live here on the beach aren't too thrilled about that. But my science teacher says those mats used to be all built up over the reefs, so at least now it'll be easier for the corals in the water to get the sunlight they need to grow.  How messed up is your beach now? Your dad always talks about stuff to do to stop erosion - Did any of that help?  -Clara

Wait, what exactly defines a beach?  Click HERE for the answer.
Click HERE for a diagram of a beach!
 
 

date: Wednesday, September 30, 1998  from: Rosa@OceanViewHotel.Biloxi.net  to : Clara_Summers@surf.Key_West.net  Hi Clara,  Yeah, my Dad takes all those anti-erosion measures pretty seriously. Erosion has always been a nightmare on this beach. For a few months every year the waves hit the beach at an angle. That starts up a longshore current - if you put a beach ball in the water and let it float, you can see it move down the beach. The current moves sand down the beach, too, so Mom and Dad built groins on our beach to trap the sand. After a few months of that, the neighbors started calling to complain that our groins made their erosion problems worse! Plus, when there's a storm, the waves are higher and steeper than usual, and they wash the sand offshore to make sandbars. But when it's calmer, a lot (but not all) of that sand is brought back by the gentler waves.  Besides the groins, Mom and Dad renourished the beach last year. It was a lot of fun to see all those loads of sand being brought in and put down. The stuff they do to stop erosion works OK everyday, I guess. But it sure wasn't a match for a hurricane like Georges!  Georges hovered over the Gulf of Mexico for a while after he left the Keys, and he got stronger. When he hit here, the wind speeds were 110 miles per hour - nearly a category 3 storm! In a hurricane like that, the winds are so strong onshore that the waves come in much higher. They take sand inland, and they even erode the dunes on the back of the beach.  Yikes, I didn't realize the time. I've got to go; I'm baby-sitting tonight. By the way, are you still going out with that guy Jason? Just curious. :)  -Rosa

Click HERE to learn some ways humans try to prevent or slow down the natural process of beach erosion.
 

date: Thursday, October 1, 1998  from : Clara_Summers@surf.Key_West.net  to: Rosa@OceanViewHotel.Biloxi.net  Hey Rosa,  I never really dated Jason - he's kind of dweeby anyway. But actually, I did meet a guy in an on-line chat room this week. I was there checking out information on beach erosion for my science project. His name is Tomas, and he lives in Honolulu! Actually, he's interested in beach erosion stuff too, because he lives near the water. He says the sea level is rising there, and his family is losing land (although pretty slowly, but still).  That made me wonder if the sea level is rising here, too. I found out that it is. It's because the Earth is warming - It's called the greenhouse effect. Gases like carbon dioxide (CO2) build up in the atmosphere from pollution, cutting down the rain forests, and other stuff that humans do that use up energy. Anyway, those gases are called greenhouse gases, and they act sort of like the security guards at school. They let sunlight into the earth's atmosphere, but they block the heat that tries to escape, because it has longer wavelengths.  So the Earth warms up and some of the ice in the polar icecaps and glaciers melts. Plus, the water in the ocean actually takes up a little more room when it's heated. Both of those things make sea level rise. It's pretty slow - one or two millimeters per year on average. But a little bit of sea level rise can cover a lot of beach. In the next fifty years, beaches around the world will be between sixteen and thirty-two feet further inland! This is pretty cool stuff - I should have a great science project.  Sea level rises depending on where you are, though. Some places farther north (or south, close to Antarctica) are weighted down by glaciers so when the ice melts, the land actually rises. But Honolulu is different. The Hawaiian islands are volcanic - they formed when the crust of the Pacific moved over a hotspot: a big plume of molten magma from the mantle (say that 5 times fast!) way below the surface of the Earth. As the islands move away from the hotspot, they cool down and sink into the ocean, even if the Earth weren't getting warmer. So the sea level rise in Honolulu is faster than most other places in the U.S. It's kind of neat to think about how the Earth will look 100 years from now, but kind of scary too.  -Clara  P.S.  You really should check out this web site - http://coastal.er.usgs.gov/hurricanes/georges The United States Geological Survey took pictures of the beaches in the Caribbean, the Florida Keys and the northern Gulf coast before and after hurricane Georges hit.  The differences are amazing!

 

As you can gather from Rosa and Clara's experiences, the beaches are in a constant state of flux. Assaults on the beach can be sudden and fast, as in a storm or hurricane. The changing seasons also leave their signature on the beaches as they bring different patterns of wind and rain. Every few years an El Nino or La Nina event brings unexpected floods and droughts which also affect beach shape.

Beaches also change on much longer time scales. During the last ice age, for instance, the sea level was much lower than it is today, so all of those beaches are now underwater. And perhaps most importantly, we know that the agents of change can be human. Building beachfront hotels, seawalls and groins, while often attractive options in the short run, can dramatically alter the natural shape of the shoreline in the long run.

All of these forces - and more - act on the beach at any given time. The beach leads an incredibly dynamic life - just like Rosa and Clara - and just like anyone else who leaves their fleeting footprints on the sand.