ABSTRACT Subsidence is one of the major processes driving coastal land loss in Louisiana. In an attempt to better understand local conditions influencing this process two continuously cored borings were taken in the Terrebonne Parish wetlands of the Lafourche delta complex. These borings were of sufficient length to completely penetrate sediments of the thick Holocene Mississippi River valley fill. One boring, 140 ft (42.6 m) long, was collected in western Terrebonne Parish under US Corps of Engineers support while the eastern Terrebonne Parish boring, 200 ft (61 m) long, was sponsored by the US Geological Survey. X-ray radiography revealed that the sediments of each boring were composed of cyclic depositional events. Each cycle basically incorporates a coarsening upward sedimentary sequence and may be described as a parasequence within the Holocene systems track. However, a wide range of sedimentary environments are represented from brackish/marine bay sediments to once exposed natural levees of major channels. Geochemical testing, particularly of carbonates and sulfides, radiocarbon dating of appropriate materials, and cone penetrometer profiling of the eastern Terrebonne boring site provided an initial data base for evaluation of effects of lithology and diagenesis on subsidence.

ABSTRACT A joint federal-state effort has been initiated in Louisiana to reduce current 6,000 hectare annual coastal wetland losses and restore wetland building in the Mississippi River delta. At $50 to $60 million annually, this initiative ranks with efforts in Florida and California as among the most ambitious habitat restorations yet undertaken. It is proposed that slurry pipelines be considered as modern surrogates for natural distributary channels in a subsiding delta tightly managed for navigation, flood control, fisheries and energy development. A twenty year scenario is proposed as one example of how funds available today might be used to stabilize wetland loss by building, saving and maintaining wetlands using a pipeline-based infrastructure to transport sediments. This model predicts that stabilization, or “no net loss” of coastal wetlands, could be achieved after 16 years.