Estimating the effects of rising seas on a particular coastline requires more than an accurate assessment of sea level rise, said Anderson. Local geography and geology also play a role. For instance, the coastal plains of southeast Texas and Louisiana are a vast sedimentary plain that is sinking at the rate of about 20 centimeters per century. Moreover, there are other geological forces at work that can be impacted or even overwhelmed by rising seas.
"On geologic time scales, barrier islands like Texas' Galveston and Padre islands retreat toward land," said Anderson. "The Galveston shoreline, for example, is moving about 1.5 meters inland every year. But the same forces that are slowly eroding the beaches on the windward side of the island deposit that sand on the leeward side, so the island itself remains a stable barrier, even though it marches slowly toward shore."
Anderson's research has found that rising seas can overwhelm fragile coastal structures like barrier islands and river delta headlands, the vast wetlands that are deposited by rivers when they empty into the sea. He began studying the geography of the U.S. Gulf Coast about 15 years ago. Four of his students -- Alex Simms, Kristy Milliken, Jessie Maddox and Patrick Taha -- are presenting new research Nov. 7-10 at the GSA's annual meeting in Denver. Much of the new research was done in collaboration with one of Anderson's former students, University of Alabama Professor Tony Rodriguez.
The findings are drawn from analysis of seafloor cores and other experimental data collected by Anderson's group, which has used ships and barges to drill cores and take underwater soundings from the southern shores of Texas to Alabama's Mobile Bay. Analyses have begun to yield a catalogue of reactions that Gulf coastal features undergo in response to specific rates of sea-level rise.