Gulf Coast Shoreline Erosion: A Complex Engineering Geologic Problem
Christopher C. Mathewson
Texas A & M University, College Station, TX
The loss of Gulf Coast shoreline property is a costly problem that adversely impacts the public, coastal homeowner, state parks and industry, to name a few. Natural and human enhanced processes contributing to shoreline erosion include sea level rise, land subsidence, coastal storms, sediment starvation, coastal construction and dredging, sand mining, coastal protective devices and water resource development. The general public, engineers and coastal resource managers all too often recognize only the localized natural or human induced processes, such as coastal structures and channel dredging and diversion, and fail to consider the significance of longer-term geologic processes, such as subsidence and sea level rise, or regional scale human activities, such as the construction of water resource structures (dams) on the rivers draining to the coast. Examples include: 1) a study of the relationship between upstream Brazos River dam development and shoreline erosion at Sargent Beach, Texas determined that there is a direct link between the area of the drainage basin downstream of a dam and the rate of shoreline loss; 2) construction of a seawall along Galveston Island, to protect the city from hurricane storm surge, resulted in the removal of a temporary storage area for excess sand (dunes) and the eventual loss of the entire beach in front of the seawall and 3) engineered stabilization of the Mississippi River System has resulted in the diversion of significant amounts of sand into dredged material disposal areas along the river or to the deep water Gulf of Mexico, both of which starve the coast of a critical sand supply. Shoreline erosion and the associated human losses related to this natural geological process demand a full scale engineering geological investigation that is regional to local in scale and recognizes both natural and human processes and their interaction.