Unprecedented coastal response to Global Change: A case study of the upper Texas Coast

There is strong scientific consensus that the rate of sea-level rise in the northern Gulf of Mexico has accelerated from an average rate of ~0.6 mm/yr over the past ~2,000 years to a current rate of ~2.0 mm/yr in response to oceanic warming and glacial melting. Subsidence is far more variable across the Gulf Coast, but there are areas where current subsidence rates far exceed the long-term background rates and therefore indicate anthropogenic influence, in particular subsurface fluid extraction. The impacts of combined eustatic rise and subsidence are exacerbated by alterations in sediment supply to the coast, which result from climate variability and human engineering modifications to coastal rivers. Hurricanes serve mainly to punctuate these other impacts. In the geologic past, the barrier islands of Texas have exhibited highly variable response to sea-level rise, some retreated rapidly while others remained stable and even advanced. Hence, simple inundation models do not capture the complex response of barriers to the combined effects of relative sea-level rise, variations in sediment supply and storm impacts. One of the best-documented cases of unprecedented erosion in modern time is Galveston Island, Texas. Based on a detailed sand budget analysis, we estimate that erosion of the island has at least doubled during historic time relative to the geologic past. Other barriers, including South Padre Island, are currently eroding at unsustainable rates compared with their geologic histories. Yet, Texas remains in a state of denial about the realities of global change and impacts on coasts. For example, the City of Galveston has continued to discourage pressures to establish a set-back rule for new construction along the beach. In an effort to better convey science to policy makers, the Gulf of Mexico Coastal Science Consortium was formed.