COLLEGE STATION, Texas -- For the past 50 years, erosion on Galveston Island has claimed as much as 10 feet of shoreline a year. It's a problem that's particularly visible on the island's west end, where there is nothing in place to buffer the waves or capture the sand as currents move it along the coastline.
Over the years, officials and homeowners have experimented with different ways of controlling erosion -- installing long tubes filled with sand (or geotubes) between the beach and homes and trucking in sand to replace that lost to erosion.
In a project funded by Texas Sea Grant, Texas A&M University at Galveston's Thomas Ravens is studying the effectiveness of these erosion-control methods as well as how much sand is being lost, how much is being gained and how it's being carried around in offshore water currents.
Ravens said that by first measuring how much sand is being lost and gained on Galveston beaches and how much sand is being transported in water currents, researchers can then use this information to devise the most appropriate control methods for different locations.
"A lot of people think -- perhaps rightly -- that the solution to coastal erosion is beach nourishment, putting more sand on the beach," he said. "But in order to do that, you need to know how much sand you're losing in the first place. The first part of our study will answer that question and allow managers to go in and say how much sand they need to supply to compensate for erosion."
Under normal circumstances, rivers carry sediment to coastal areas, and currents flowing parallel to the coastline distribute the sand to the beaches, replenishing sand lost to erosion. But as humans dam rivers, Ravens said, this sand source is cut off, and the amount of sand making it to the coast is not enough to make up for that lost to erosion.
Meanwhile, global water levels are rising and parts of Galveston Island are sinking because of the pumping out of groundwater, oil and gas, he said. All of this leads to greater erosion rates. Galveston is already at a disadvantage because its beaches are so flat. For every 1-meter rise in water level, Ravens said, Galveston loses 100 meters of beach to the Gulf of Mexico.
"We suffer because our beaches are so flat," he said. "Just a little change in elevation of the water leads to a big change in terms of where the shoreline is because the slopes of the beaches are so low."
Gradually sloping beaches are just one of the factors that distinguish Gulf Coast beaches from those on the East or West coasts, he said. The other is the fine sediments found in the Gulf region. Because of these differences, Ravens said, erosion and sediment transport models developed for the other two coasts are not effective for predicting conditions along the Gulf.
Ravens said the project includes creating sediment transport models and equations that will be specific to the Gulf Coast. People will be able to use these to predict what will happen if, for example, a breakwater or geotubes are installed along Galveston Island.
"This kind of information about exactly what's happening in nature will be very valuable for people whose job is to manage and plan for nature's contingencies," he said.
The National Sea Grant College Program is a partnership of university, government and industry, focusing on marine research, education and advisory service. The Sea Grant Program is a practical, broad-based effort to promote better understanding and use of marine resources through research, education, extension and information transfer.
The above story is based on materials provided by National Sea Grant College Program. Note: Materials may be edited for content and length.
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