A Conceptual Hurricane Surge Protection Plan for Coastal Louisiana

摘要

The coastal wetlands and estuaries of Louisiana are one of the world's great ecosystems. For millennia, the Mississippi River has supplied the coast with an immense resource of freshwater, nutrients, and sediment to build a vast expanse of marsh and swamp land. Millions of people rely directly or indirectly on the marshes for their livelihood and for protection against hurricanes and storms. In the last several decades humans have impacted this ecosystem in many ways, especially by controlling rivers so natural floods are no longer a part of wetland maintenance and creation, and by building channels that expose freshwater marshes to salt water at an unnatural rate. As a consequence the natural surge buffering offered by the wetlands has been severely reduced. Louisiana is thus very vulnerable to hurricanes and major flooding as 70 percent of the population lives on 36 percent of land at or below sea level. Hurricane Katrina made landfall in Louisiana as a moderately fast-moving Category 3 hurricane the early morning of 29th of August, 2005. In greater New Orleans the flooding cost the lives of more than 1,500 residents and over 100,000 families were rendered homeless, the great majority of whom had heeded evacuation orders. The 1927 Mississippi River flood prompted a complete redesign of the Nation's strategy for managing the lower Mississippi River leading to construction of the Mississippi River & Tributaries Project (MR&T) that has successfully prevented a repeat of the 1927 disaster. In contrast, many observers have noted similarities between the patterns of surge-induced flooding that occurred during Katrina and the previous storm of record, Hurricane Betsy in 1965. The greater New Orleans hurricane protection system was, in fact, intended to prevent a repeat of Betsy disaster, but this system failed during Katrina with catastrophic results. A hypothesis for the a long-term hurricane protection system is presented for coastal Louisiana that focuses on levee systems coupled with wetland creation, restoration, and maintenance and has as its central theme, delivering sediment and fresh water from the Mississippi. This ‘survival’ plan would not be cheap; however, it will ensure the continued existence of coastal Louisiana, its inhabitants, and unique culture.