LOUISIANA COASTLINE RESTORATION EFFORTS: THE SEARCH FOR SAND

High rates of coastal erosion along Louisiana have prompted the proposal of numerous restoration and preservation projects for critical segments of the Louisiana shoreline. The goal of these projects is to reconstruct and replenish the disappearing shoreline through the placement of sand-rich sediment. The success of these projects depends upon the presence and identification of texturally suitable offshore sediment. Additionally, restoration projects are being proposed faster than sand resource surveys can be completed. Consequently, currently proposed restorations may be unfeasible because of a lack of economically recoverable sand. An a priori knowledge of sand distribution on the shelf would provide restoration scientists with the information necessary to submit the most feasible restoration proposals. This study investigates the use of multivariate statistical procedures to document and predict the stratigraphic variability of sandy sediment for a section of Louisiana shelf, on the basis of data obtained from an adjacent section of the shelf. One such statistical approach is cluster analysis using more than 2000 individual grain-size analyses for samples taken from approximately 200 vibracores. Our preliminary analysis identified three clusters within the study area, which are internally homogenous and externally heterogenous, especially with respect to sand distribution. For simplicity, the geographically smallest of the three clusters was selected for study and further subdivided into two sites. Sand percentages at nearly 50 locations within each site served as the real data. Scatterplot smoothers were used to find the trends of sand distribution in Site A and used to predict sand percentage trends within Site B. Results indicate that predicted trends closely matched the observed data. The utility of statistical approaches to identifying sand is that sand distribution can be determined using reconnaissance surveys and a smaller number of vibracores than would otherwise be taken. However, the complexity of fluvio-deltaic processes may be a limiting factor to the application of this technique over large areas of the Louisiana shelf.