Our Coast to Fix -- or Lose
There has been much debate in the past 20 months over protecting Louisiana from another lethal hurricane, but nearly all of it has been conducted without any real understanding of the geological context. Congress and the Bush administration need to recognize six facts that define the national interest.
· Fact 1: The Gulf of Mexico once reached north to Cape Girardeau, Mo. But the Mississippi River carries such an enormous sediment load that, combined with a falling sea level, it deposited enough sediment to create 35,000 square miles of land from Cape Girardeau to the present mouth of the river.
This river-created land includes the entire coast, complete with barrier islands, stretching from Mississippi to Texas. But four human interventions have interfered with this natural process; three of them that benefit the rest of the country have dramatically increased the hurricane threat to the Gulf Coast.
· Fact 2: Acres of riverbank at a time used to collapse into the river system providing a main source of sediment. To prevent this and to protect lives and property, engineers stopped such collapses by paving hundreds of miles of the river with riprap and even concrete, beginning more than 1,000 miles upriver -- including on the Ohio, Missouri and other tributaries -- from New Orleans. Reservoirs for flood protection also impound sediment. These and other actions deprive the Mississippi of 60 to 70 percent of its natural sediment load, starving the coast.
· Fact 3: To stop sandbars from blocking shipping at the mouth of the Mississippi, engineers built jetties extending more than two miles out into the Gulf of Mexico. This engineering makes Tulsa, Kansas City, Minneapolis, Cincinnati, Pittsburgh and other cities into ports with direct access to the ocean, greatly enhancing the nation's economy. The river carries 20 percent of the nation's exports, including 60 percent of its grain exports, and the river at New Orleans is the busiest port in the world. But the jetties prevent any of the sediment remaining in the river from replenishing the Louisiana and Mississippi coasts and barrier islands; instead, the jetties drop the sediment off the continental shelf.
· Fact 4: Levees that prevent river flooding in Louisiana and Mississippi interfere with the replenishment of the land locally as well.
· Fact 5: Roughly 30 percent of the country's domestic oil and gas production comes from offshore Louisiana, and to service that production the industry created more than 10,000 miles of canals and pipelines through the marsh.