Geological Mapping of Subsidence in New Orleans

The Mississippi River deltaic region of southeastern Louisiana is made noteworthy by the challenges presented to engineers in the design, construction, and maintenance of sustainable structures on a very unlikely site for a metropolis. Subsidence, the relative lowering of a land surface with respect to sea level, has long been recognized as a serious problem in the city of New Orleans. The area is subsiding due to both natural and man-made causes, including sediment compaction due to the unconsolidated nature of the geologically young soils, downwarping of the Gulf Coast Geosyncline due to sediment loading, leveeing of the Mississippi river (thereby prohibiting sediment replenishment during flood stage), oil and gas extraction, lowering of the water table through groundwater withdrawal and an increased surface area of paved surfaces, and, to a minor extent, faulting. There is still much research being done as to the extent that each of these causes affects the rates of subsidence, as many of the processes are deep seated and therefore cannot be directly observed. In a city where sustainable structures such as the hurricane protection systems are imperative to its survival, these studies are of the utmost importance in order for engineers to more accurately forecast subsidence rates over an extended period of time. Using geological mapping of the underlying strata, locations of the boring holes by which these maps were made, and detailed satellite mapping of subsidence rates over a three year period, this study will begin correlating settlement to the underlying geological strata