"What happens to a beach depends on randomly occurring storms, and every storm is different," he said. "You have some big storms that don't do anything. Then the next big storm will do a tremendous amount of damage."

Beaches can behave chaotically, which -- according to the emerging guidelines of chaos theory -- "have a huge dependence upon initial conditions," added Pilkey, who said his "favorite initial condition" is a layer of shells that can cover some beaches.

"If you have a shell layer, the beach won't move until you are well into a storm and the energy gets really high," he said. "Whereas, with a beach that is less shelly, its sand will move with the waves from the beginning of a storm. So you have an entirely different response to a storm just because of a layer of shells."

Pilkey said such models also do not keep up with the pace of scientific discovery.

For instance, he said, coastal researchers learned only comparatively recently that "rocks underlying the shore face control the erosion rates of beaches. These models also don't take into account the strong bottom currents that we didn't know much about 20 years ago."

Pilkey stressed that he does not object to using "basic" scientific models to study nature, because those address the questions "how" or "why." By contrast, the engineering models he opposes "ask the questions "where," "how much" and "when," he added.

"For example, "When will that beach disappear that we just nourished?" he said. "Or, "How much sand will be needed to make it last for X numbers of years?"; and "Where is the shoreline going to be
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Contact: Monte Basgall
Monte.basgall@duke.edu
919-681-8057
Duke University
25-Jan-1999