The Role of Geology in Coastal Engineering Challenges Along the Gulf Coast

Roy K. Dokka
Louisiana State University, Baton Rouge, LA

Most activities of geologists studying modern processes along the gulf coast of the USA have focused on topical issues such as infrastructure, coastal erosion, wetlands loss, and subsidence, with varying degrees of success. Geologists with oceanographic backgrounds have greatly helped engineers better understand the shifting patterns of sediments and landforms over time. For example, the ephemeral nature of barrier islands are now firmly understood (but not generally heeded!), offshore pipelines are located more wisely, and the consequences of dredging are better understood. Furthermore, fluvial and deltaic geologists accurately predicted the accelerated demise of the modern Mississippi River delta due to the construction of river levees. The relationship between sediment accretion and subsidence was demonstrated by geologists as early as the mid-1800s! Geologists with backgrounds in biological processes have demonstrated that if natural processes were restored to the wetland areas, sediment productivity could very well match modern rates of subsidence and eustatic sea level rise. Unfortunately, a similar level of understanding of the processes causing subsidence has not been reached due in large part to the lack of accurate and precise measurements of modern vertical change. Until recently, modern (past 50 years) subsidence rates were derived from studies of process change averaged over hundreds and thousands of years. New and exciting new insights are being provided by traditional geodetic measurements and space technologies such as GPS, Lidar, and Radar methods.