Land Loss Rates. Report 3. Louisiana Coastal Plain

Land Loss mapping and rate curve development for 62 quadrangles in the Louisiana Coastal Plain shows that land loss rates and trends vary significantly throughout coastal Louisiana. Land loss rates for each quadrangle were defined for 4 time periods 1930s to 1956-58, 1956-58 to 1974, 1974 to 1983, and 1983 to 1990. Differences in land loss rates among the individual quadrangles are a function of the geologic and hydrologic setting and the factors which contribute to land loss such as subsidence, storm induced erosion, channelization of streams and rivers, and canal dredging. Of the 62 quadrangle mapped, 9 quadrangles are losing more than 1 percent of their land area each year, and 12 quadrangles are losing between 0.5 and 1.0 percent per year during the 1983 to 1990 period. On a regional scale, the land loss rate for the entire Louisiana Coastal Plain has decreased from an average yearly rate of 41.83 square miles in the 1956-58 to 1974 period to 25.34 square miles during the 1983 to 1990 period. The percentage of land being lost is also decreasing from 0.51 percent per year in the 1956-58 to 1974 period to 0.35 percent per year during the 1983 to 1990 period. The regional land loss rate will probably continue to decrease slowly until a background rate is reached. Coastal Louisiana, Mississippi River Deltaic Plain, Land loss, Wetland loss, Louisiana Chenier Plain, Wetlands.