Comparing and Contrasting the Benefits of Land Mass vs. Land Cover on Storm Surge Attenuation

Abstract:

From 1930 through 2012 Louisiana lost approximately 1,880 sq mi (4,870 sq km) of coastal wetlands due to land subsidence, erosion, and sea level rise among other factors. Louisiana could potentially lose an additional 1,750 sq mi (4,530 sq km) of coastal wetlands by 2062 if no action is taken to prevent this land loss (CPRA, 2012). If risk is defined as probability multiplied by consequence (Vrijling, 2006), such land loss will significantly increase the risk of flooding in coastal communities and communities located farther inland. Vital coastal infrastructure will also be at a heightened risk of flood damage. This will be attributable to the increase in frequency of hurricane storm surge events featuring greater depths and farther inland extent. This risk can be described by contrasting the surface area of land and water along the Louisiana coast. Using aerial or satellite imagery, isopleths can be plotted along the coast that describe the land to water (L:W) ratio over time (e.g., Gagliano et al., 1970, 1971 plotted the calculated 50% L:W ratio isopleths for the years 1930, and 1970, with an estimated 2000 isopleth). Risk to coastal infrastructure and coastal communities increases as the L:W ratio is reduced.

One possible way to reduce the depth and extent of storm surge is to increase the land area along the coast. A second way is to modify the land cover (i.e. vary the type and density of vegetation). The L:W ratio can be used to quantify storm surge attenuation and assess such contributing factors. For this study, storm surge is simulated along coastal Louisiana for various instances – with increased land area and separately with different land cover types and densities – to determine which of these factors most effectively reduce the depth and extent of storm surge. New metrics involving hydrologic basins for evaluating storm surge attenuation are also described. The results of this study should inform policy makers which factors contribute the most to storm surge attenuation and risk reduction along the Louisiana coast.