Coastal Defense
Think again about your sand castle on the beach. If you want to prevent it from washing away in a wave, what can you do? You have to find a way to defend your castle.
Coastal defense includes all of the methods used to protect shorelines from the effects of erosion. You have been able to discuss some ideas about coastal defense with your classmates. Now check out each image to learn about some methods that are currently in use. Do any of them resemble your own ideas?
Groynes are wooden, concrete, or rock barriers built perpendicular to the sea. Sand builds up on one side and helps slow down erosion. But sand does erode from the other side of a groyne, so many groynes must be built in succession to each other. Groynes require very little maintenance, but many coastal communities find them unattractive, so they are decreasing in popularity.
Seawalls can be built along beaches to diminish the energy of waves. They can be likened to armor that protects the shore from wave pounding and the energy of destructive waves.
Riprap is a collection of large rocks placed along a shoreline to protect it from the energy of breaking waves. It has the advantage of being effective against wave pounding. But it does not stop longshore drift, and it rarely holds up during a severe storm. It also reduces the recreational value of a beach and is unpopular with tourists and other beachgoers.
Gabions are mesh cages filled with boulders and rocks that are placed in front of areas vulnerable to erosion. The disadvantage of these is that they wear out quickly and are not very attractive to recreational beachgoers.
Breakwaters are enormous stone structures sunk offshore to alter wave direction and diminish wave energy. Waves break further offshore, thus reducing their erosive power.
