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Dunes: Galveston’s First Line of Defense

Galveston's First Line of Defense

Last Updated: August 10, 2020 by Steve Alexander | Nature


With hardly a glance, beach visitors pass piles of sand on their way to the waves, their eyes straight ahead, searching for a good spot to settle. But it’s not the water’s edge they seek that’s the most important part of the shore. That distinction belongs to the beachfront dunes on the upper beach, the part that protects all behind it.

Those piles of protection take time to form. Waves deliver sand to the shore grain by grain. Those grains are picked up by onshore winds and blown up the beach in ground-hugging fashion, in movements similar to ghostly apparitions. Sand grains move along until they settle against an obstacle, any obstacle — a shell, a piece of driftwood, a dead fish or seaweed.

Sand Fencing
Sand Fencing to Build Dunes Photo by Steve Alexander

That’s the strategy behind the human practice of placing bales of hay, Christmas trees and sand fencing on the beach. Like the obstacles delivered naturally to the shore, each of these represent an obstacle to movement, where sand settles and stays put.

Beach Morning Glory Growing on Dunes Photo by Steve Alexander

In time, a sand pile forms against an obstruction and continues to grow slowly. After months, piles grow large and high enough to serve as fertile ground for wind-blown seeds. Seeds settle, germinate and grow, sending roots downward and long runners outward, slowly growing their footprint in the sand. Their anchoring roots and widening presence encourages more grains of sand to stop, thus growing the pile, both higher and wider.

Sea Purslane Growing on Dunes
Sea Purslane Growing on Dunes Photo by Steve Alexander

These piles become what Richard Davis called coppice mounds in his book Beaches of the Gulf Coast. They ultimately join together to form dunes, those proper-looking ridges that extend along the upper shore.

Dunes are important, especially during hurricane season, because they function as an effective barrier against high water and storm surge. Galveston’s seawall serves that purpose as well, but it’s the beachfront dunes that serve as Galveston’s first line of defense against the sea.

So, on your next beach outing, take a look around as you head for the waves. And maybe this time, you’ll linger a bit longer.

Steve Alexander

Steve Alexander teaches wetlands management at Texas A&M University at Galveston and is a member of the Board of Directors of the Galveston Island Nature Tourism Council. He is the author of Exploring Galveston: A Naturalist's Guide to the Island.

Steve Alexander
2020-08-10T11:25:52-05:00

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