Scientific Symposium Presentation Abstracts
September 19
Dr. Virginia Burkett: The Gulf Coast: Increasing Vulnerability to Storms and Sea Level Rise
The northern Gulf of Mexico coastal zone has some of the highest rates of coastal erosion and wetland loss in the world. The most rapid and extensive coastal retreat occurs during frontal passages, hurricanes and lesser tropical storms. As the atmosphere and sea surface warm, tropical storms are likely to become more intensive, portending accelerated erosion of shorelines and tidal marshes. Some studies suggest that the destructive capacity of Atlantic Basin hurricanes has already started to increase in response to the increased greenhouse gas emissions of the past 120 years; others suggest that a natural, cyclical increase in hurricane intensity is underway, which would also increase the vulnerability of the Gulf Coast to storm surge flooding and erosion. During Hurricanes Katrina and Rita in 2005, for example, about 300 square kilometers of land in south Louisiana were converted to open water according to preliminary surveys.
Even if hurricanes do not increase in frequency or intensity over the next century, flooding is likely to increase along the low lying Gulf of Mexico shoreline as sea level continues to rise. Most of this coastline is classified by the U.S. Geological Survey as “Highly Vulnerable” to erosion due to sea level rise. Compounding the exposure to rising sea level, large areas of the Gulf Coast are experiencing land surface subsidence due to human development activities such as groundwater and hydrocarbon withdrawals, drainage of organic soils, and sediment deprivation caused by flood control levees and other hydrologic modifications. Geologic records indicate that global sea level has risen about 120 meters since the Last Glacial Maximum approximately 20,000 years ago. Sea level rose rapidly (averaging almost 0.9 m per century) between 20,000 and 6,000 years before present and slowed to about 0.02 m per century or less during the past 3,000 years. From the mid-19th century through much of the 20th century, the rate of global sea level rise increased to between 0.1 and 0.2 m per century, and satellite data for the last decade suggest that the contemporary rate is as much as 0.3 m per century. Virtually all atmosphere-ocean general circulation model simulations project that sea level rise will accelerate further due to human-induced warming. If the rate of sea level rise increases as anticipated, the Gulf coast and other low lying coastal mainlands, barrier islands, and wetlands that are not experiencing significant uplift will be adversely affected.
Human development patterns are a third component of vulnerability to climate change for human communities along the northern Gulf Coast. Wetlands, barrier islands and floodplains across the entire region have been developed for agricultural, municipal and industrial use. The exposure of human communities and infrastructure to flood damages are generally high because of their elevation relative to sea level, proximity to the shoreline, and the lack of design features that would accommodate a changing environment.
