The Multiple Lines of Defense Strategy to Sustain Coastal Louisiana

Coastal Louisiana has entered a period when the convergence of at least two powerful processes is working against its survival. Meteorological processes driving tropical systems have more frequently generated category 4 and 5 hurricanes and, although not a certainty, more destructive hurricanes are predicted for coming decades. Since the 1950s, the processes driving coastal land loss in Louisiana have continued only slightly abated. A deteriorating coast and historically inadequate levees make Louisiana acutely susceptible to the negative consequences of hurricane surge events. Coastal Louisiana's crisis of vulnerability is the continued temporal overlap of weakened hurricane protection with more frequent, intense hurricanes. The multiple lines of defense strategy proposes that two essential elements of the Louisiana coast be managed and perpetuated, which together can economically sustain the coast. The two planning elements are (1) using natural and manmade features (lines of defense) that directly impede storm surge or reduce storm damage and (2) establishing and sustaining habitat goals. The strategy can be broadly considered as integration of structural and nonstructural flood protection with coastal restoration. Extensive storm surge modeling by the U.S. Army Corps of Engineers has verified the presence of critical landscape features, which are existing lines of defense that beneficially impede storm surge. The proposed strategy is potentially a unifying vision for the coast: embracing environmental habitat restoration as well as engineered flood protection. Application of the strategy is more consistent with traditional land use than modern land use in coastal Louisiana. The multiple lines of defense strategy goals can be articulated through maps and tested with hydrodynamic and habitat models. The paramount product of this planning is a single map indicating the desired future elements of the coast that provide essential ecologic services and an adequate regional flood system to perpetuate the economy of the region.