Coastal Erosion and Engineering Solutions

Coastal Erosion and Engineering Solutions


Coastal Erosion and Engineering Solutions

Most beaches, if left alone to natural processes, experience natural shoreline retreat. (One of the reasons for the shoreline retreat is the gradual warming trend of the earth; the warming trend is a fact, regardless of whether one agrees that greenhouse gases are a cause of the global warming.) The beach retains its shape and width as it retreats, but changes its location gradually inland. As humans put houses, highways, seawalls and other structures on or close to the beach, the natural shoreline retreat processes are interrupted. The beach jams up against these human made obstacles and narrows considerably as the built up structures prevents the beach from moving naturally inland. In many coastal locations, it's a question of beaches or buildings. And hard stabilization structures to save beachfront buildings only serve to accelerate the beach erosion.

The following principles have made engineers indignant and angry, but they are proven by careful observation of coastal engineering and its consequences:

No erosion problem exists until people lay out property lines and build. Beach changes only trouble people who have strong attachments to immovable objects and fixed lines. Shoreline engineers are rarely, if ever, called in to stabilize a wild beach. Anything built on or near the beach usually increases the rate of erosion. Seawalls, bulkheads, groins, and house foundations reduce the flexibility of the system to respond to changes in the dynamic equilibrium. If energy patterns and sea level change and the beach does not, residents will lose more beach than under the natural system. Once you start protecting the beach you can't stop. By destroying the beach, most protective measures eventually create peril for themselves and increased danger to the development they protect. When protective seawalls or artificial dune walls or jetties begin to give way, a healthy natural system does not exist as a backup. Also, residents seeing a seawall crumble often feel more frightened of the ocean than those watching natural erosion. The sequence of beach protection is also a sequence of increasing expenses.

In order to "save" the beach, we destroy it. When we stop erosion it is not to save the beach, but the development behind the beach. The beach that has become inflexible disappears rapidly, as it did at Miami Beach. The cost of saving property is greater than the value of the property saved. This is particularly true when the long-range costs are accounted for and we recognize that storms occasionally wipe out whatever defenses have been erected.

Sources:

The Beaches Are Moving: The Drowning of America's Shoreline, by Wallace Kaufman and Orrin Pilkey, Anchor Press/Doubleday, 1979, pgs. 191-192 .

The Corps and the Shore, Orrin Pilkey and Katharine Dixon, Island Press, 1996, pgs. 34-60.)

Mark Babski, The Surfrider Foundation; Coastal Factoids are updated daily on the web at http://www.sdsc.edu/surfrider.


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