ABSTRACT

The land surface of the New Orleans area is subsiding in a manner similar to that of other deltaic deposits in the Gulf Coastal Plain. Superimposed on this broad subsidence pattern is another (more local in nature) that is associated with the lowering of the piezometric surface of the principal aquifer of the area, the "700-foot" sand. Published elevations of bench marks show an elevation decrease of as much as 1.7 feet between 1938 and 1964. The long-term implications to the city of New Orleans of the subsidence produced by ground-water offtake are significant. The land surface is already so low that additional subsidence should not be tolerated. Ground-water offtakes should not be increased; if possible, ground-water production within the area should be curtailed. If the aquifers (primarily the 700-foot sand) are to be used in the future, they should be artificially recharged to reduce the net withdrawal of water.