Every now and then, my research group takes a trip down to the Gulf Coast to discuss barrier island stability and collect sediment cores. Galveston Island’s foundation was built over a timespan of about 4000 years during the Holocene by prograding, or building out in a seaward direction, as a result of sand being supplied to the barrier faster than sea level rise could remove it. However, over the past 2000 years, Galveston’s shoreline has been retreating landward, most significantly during this century. Right now, the shoreline is retreating at rates up to ~4 m/yr. Through seismic records, we know the location of Galveston’s maximum seaward extent at about 2000 years ago. If we take that shoreline and use the present-day retreat rate to estimate where the shoreline should be today, we find that the shoreline would be nearly 3 miles (4.7 km) inland to where it is now! This tells us that the modern retreat rate is unprecedented, and that retreat must have been much slower over the majority of the 2000 years than it is today.
Two years after the catastrophic Galveston Hurricane of 1900, the city began construction of a 17-foot high, 10-mile long seawall to protect the city from future storm surge. The west end of the Galveston Island seawall was completed in 1963 but does not span the whole island. In 55 years, the shoreline of the unprotected side has retreated substantially. See the GoogleMap below marking the sharp boundary between the east side of Galveston that is protected by the seawall and the west side that is unprotected. I took the photo below while standing at the location marked on the map, facing west.
Here are some publications related to this topic that have come out of our group over the last few years:
Odezulu, C.I., Lorenzo-Trueba, J., Wallace, D.J. and Anderson, J.B., 2018. Follets Island: a case of unprecedented change and transition from rollover to subaqueous shoals. In Barrier Dynamics and Response to Changing Climate (pp. 147-174). Springer, Cham.
Anderson, J.B., Wallace, D.J., Simms, A.R., Rodriguez, A.B. and Milliken, K.T., 2014. Variable response of coastal environments of the northwestern Gulf of Mexico to sea-level rise and climate change: Implications for future change. Marine Geology, 352, pp.348-366.
Wallace, D.J. and Anderson, J.B., 2013. Unprecedented erosion of the upper Texas coast: Response to accelerated sea-level rise and hurricane impacts. GSA Bulletin, 125(5-6), pp.728-740.