Saving the sandy shores

With an economy dependent on the bucket-and-shovel brigade, Florida certainly knows the value of its famous beaches. But storms, waves and wind can take their toll on sandy shores, which is why Florida spends $90 million a year on beach renourishment projects. That's nearly as much as the $100 million spent annually in the rest of the United States. An average-sized project, renovating three miles of beach, can total $15 million.The cost is usually divided among local, state, and federal budgets. With so much money at stake, officials want to know how well the restoration efforts will hold up.There are two methods for projecting the performance of renourishment projects. The question is, are they reliable?

Well, now we know the answer, at least for one of the methods, says Bob Dean, a civil and coastal engineering professor at the University of Florida, who conducted a study on the accuracy rates of renourishment projections. A method he and a student devised a dozen years ago offers predictions of "reasonable" accuracy, he says, after comparing the predicted outcome with the actual outcome of eight projects, some a decade old. They found the actual amount of sand remaining after a year would be between 30 percent more or 30 percent less than projected. Predictions of the size and shape of the beach were about 50 percent accurate. That's not awfully high, he admits, but it's a good first step. Dean's method also leaves no room for disagreement, he notes."It has the advantage that it requires no judgment nor calibration, and thus two individuals applying the method should obtain the same results." Dean says he learned some new things doing the study and thinks he can fine-tune his method and improve the accuracy of the forecasts. Sure beats counting the beaches one grain of sand at a time.