Land Loss Rates: Louisiana Coastal Plain

Land loss mapping and rate curve development for 62 quadrangles in the Mississippi River deltaic and chenier plains shows that land loss rates and trends vary significantly throughout coastal Louisiana. Land loss rates were defined for each quadrangle for 4 time periods (1930's to 1956-1958, 1956- 1958 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 quadrangles mapped, 8 quadrangles are losing more than 1 percent of their land area each year, while 21 quadrangles are losing more than 0.5 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 1956-1958 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 1956-1958 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.