IT happens so gradually that most of us scarcely notice: Over time the constantly rising level of the oceans takes a toll in the flooding and erosion of shoreline. The sea level is rising at an increasing rate; it could move up by as much as five feet by 2085. Melting glaciers, the warming of the atmosphere, and subsiding land in coastal areas all contribute to this phenomenon of rising waters. In the past, erosion and flooding have been most dramatic along the Atlantic coast: Waters have risen one foot over the last century. The Cape Hatteras Lighthouse, once 1,500 feet from the waves, is now a scant 150 feet away. Extent of the problem often varies with local conditions. In Louisiana, 60 square miles of land along the Gulf of Mexico is submerged each year. Raising of levees along the Mississippi River has caused the rich sediment, which once replenished Louisiana's coast, to flow right on by. The effect is one of the most pronounced drownings of a shoreline anywhere in the world.
A recent National Research Council Report urges coastal developers, engineers, and zoning experts to build with the changing water levels in mind. Washington is looking for better ways to get such data to those who could use it.
Taxpayers, too, should be concerned. The National Academy of Sciences has just been asked to calculate how coastal erosion can be factored into the federally subsidized flood insurance program. Garry Brewer and Martin Shubik, writing on the page opposite today, suggest by contrast that federal insurance to coastal private property owners be prohibited; that would compel planners and buyers to take the changing shoreline into account. This is a good idea - if phased in over time, to avoid cases of undue hardship.
Sadly, man has been able to do little to halt or reverse the trend of rising coastal waters; building more levees and sea walls tends only to delay the action.