In general, shorelines are constantly pounded by waves and storms that erode the coast. Along the Atlantic coast, an average of two to three feet of beach is lost to erosion annually. Recently, the Federal Emergency Management Agency, FEMA, looked at the effect that erosion will have on the Atlantic shoreline over the next 60 years. One of the beaches studied closely was South Bethany in Delaware.

Here's an aerial view of part of that beach. The blue line is the current location of the shore, defined by a vegetation line or the front edge of the dunes. Assuming that sea levels rise about 3 inches in the next 60 years - approximately what happened over the last 60 years - the beach is expected to erode inland to the red line by the year 2060. If that happens, the three rows of houses closest to the beach, marked with yellow circles, would be lost.

This is a graphic example of just how vital beach protection efforts, like replenishment, really are - without them, we would eventually lose the battle against coastal erosion.