Land Loss Rates: Mississippi River Deltaic Plain

Land loss mapping and rate cure development for 50 quadrangles located in the Mississippi River deltaic plain show that land loss rates calculated for the 1930s to 1956-58, 1956-58 to 1974 to 1983 time periods vary significantly throughout the deltaic plain. Differences between land loss rates of individual quadrangles are a function of the geologic setting and the factors which contribute to land loss such as subsidence, storm-induced erosion, channelization of streams, and canal dredging. Of the 50 quadrangles mapped, 14 show an increase in the land loss rate, 29 show a decrease, and 7 remained approximately the same. Specific causes of land loss are not evaluated in this report. On a regional scale, the land loss rate for the entire Mississippi River deltaic plain an area of approximately 13,000 square miles has decreased from an average yearly rate of 28.02 square miles for the 1956-58 to 1974 period to 22.97 square miles for the 1974 to 1983 period. Another data set is needed to verify whether this decrease in the average annual land loss rate is continuing. Land loss data generated during this investigation is being combined with geologic data in a Geographic Information System to facilitate detailed analyses of the causes of land loss in future reports. Mississippi river delta Land areas.