Adapting to Sea-Level Rise in the U.S. Southeast: The Influence of Built Infrastructure and Biophysical Factors on the Inundation of Coastal Areas
(November 1992)

R. C. Daniels, The University of Tennessee and Oak Ridge National Laboratory

V. M. Gornitz, Goddard Institute for Space Studies

A. J. Mehta, and S.-C. Lee, University of Florida

R. M. Cushman, Oak Ridge National Laboratory

The Earth's mean surface air temperature has increased by 0.5° C over the past 100 years. This warming trend has occurred concurrently with increases in the concentration and number of greenhouse gases in the atmosphere (e.g., CO2, N2O, H2O, CH4, and CFCs). These gases may be partially responsible for this temperature increase and may cause this trend to accelerate in the future because of the increased amount of thermal radiation that will be trapped in the troposphere by these gases. This trapping effect may result in a net increase in the earth's global mean surface air temperature of 1.5° to 4.5° C by the year 2100. An increase in the mean surface air temperature of this magnitude could cause significant increase. This increase in sea surface temperature will cause sea levels to rise from thermal expansion of the sea and the addition of melt waters from alpine glaciers and continental ice sheets.

To allow for the cost-effective analysis of the impacts that sea-level rise may have on the U.S. Southeast, a method is needed that will allow sites potentially at risk to be identified for study. Previously, no objective method was available to identify such sites. This project addresses the problem of potential coastal damage by using a geographic data base that has information on both physical and climatological factors to identify areas of the U.S. Southeast at risk to inundation or accelerated erosion as a result of sea-level rise. The following six areas were selected for further study from the many identified as being at high risk: Galveston, Texas; Caminada Pass, Louisiana; Bradenton Beach, Florida; Daytona Beach, Florida; McClellanville, South Carolina; and Nags Head, North Carolina. These six areas are representative of three of the major stages of economic development on the East and Gulf coasts (i.e., urban/residential, undeveloped/rural, and resort/recreational), consequently any conclusion drawn from these case studies may be generalized to other high risk regions with similar geologic and economic histories.

For each study area the amount of land, by land-use type, in danger from inundation was calculated for three sea-level-rise scenarios. The calculated values were based on elevation alone. These studies were then extended by considering the effects that built infrastructure (e.g., seawalls) and biophysical factors (e.g., erosion/accretion rates) would have on the actual amount of land that would be inundated if the sea were allowed to advance unchecked. By considering these factors, a best-guess estimation of the amount of land that may be lost to the sea was derived for each study area and each scenario. These estimated values consider both natural (e.g., elevation and erosion/accretion) and anthropogenic (e.g., built infrastructure) effects when predicting the future location of the coastline in the years 2050 and 2100 for each study area, for each scenario.

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