The sand on a beach is almost always on its way to somewhere else. It wants to move along the shore in response to longshore currents. It wants to pile up on the beach in the summer when the waves carry less energy, then move out to a bar just beyond the breaking surf in the winter, when the waves are stronger.
During a really big storm, with intense waves and storm surge, the sand really moves around. If you have any doubts take a look at the amazing aerial photos posted today on the NY Times website of the devastation along the New Jersey coast from Hurricane Sandy. Barrier islands often just disappear during big storms.
I am certainly sympathetic to the human cost of this destruction. But let’s face it. Building a house on a barrier island is a crapshoot, a bet that may go well for decades, especially with a little help from the Army Corps of Engineers. But sooner or later the bet will go south in a big way. Sorry to seem grumpy, but this is not some mysterious secret. It’s the physics of sand and water.