Coastal & Marine Geology Program > National Assessment of Coastal Change Hazards > Open File Report 03-337

An Overview of Coastal Land Loss: With Emphasis on the Southeastern United States

USGS Open File Report 03-337

by: Robert A. Morton

Summary Introduction Physical Agents of Land Loss: Waves, Currents, & Storm Surges Landslides & Cliff Retreat Sediment Budget Relative Sea Level Climate & Land Loss Role of Shoreline Characteristics: Composition, Induration, & Saturation Coastal Morphology & Vegetation Role of Human Activities: Introduction Transportation Coastal Construction River Modification Hydrocarbon & Groundwater Extraction Climate Alteration Coastal Excavation Wetland Losses Acknowledgments References

Role of Human Activities: Climate Alteration There is growing concern that global warming of the atmosphere from burning fossil fuels will cause continued thermal expansion of the oceans and possibly melting or disintegration of the West Antarctic ice sheet (Barth and Titus, 1984; National Research Council, 1990). The increased volume of water liberated by these processes would accelerate the global rise in sea level and cause flooding of low-lying coastal regions. Current scientific debate about future sea level conditions focuses on identifying the local components of relative sea level and how each of those components will be altered if future global warming is consistent with recent predictions. Although the causal correlation of a global rise in sea level with global warming appears reasonable, predictions of greater storm frequency and intensity as a result of altered global climate are still speculations because long-term atmospheric and climatic models are imprecise. Even meteorologists disagree as to the likelihood of exceptionally intense storms either in the future or in the past when geological evidence indicates global temperatures were warmer. Counterbalancing forces attempt to maintain fluid equilibrium by preventing development of extreme atmospheric conditions. Increased carbon dioxide in the atmosphere would increase global temperatures, but these conditions can also cause offsetting reactions such as increased cloudiness that would limit warming of the earth. Significantly increased global temperatures would shift the zone where tropical cyclones form into higher latitudes and extend the season of ice-free ocean, thus providing greater opportunity for storm influence and possibly greater land loss. But higher temperatures would also decrease thermal gradients between the poles and equator and possibly reduce the sharp temperature contrasts that are so critical to intensification of extratropical storms. Human impact on global climate has already been demonstrated; what remains unknown is how much the climate will be modified during the next century (Barth and Titus, 1984; Titus, 1988). continue to Coastal Excavation

Coastal & Marine Geology Program > National Assessment of Coastal Change Hazards > Open File Report 03-337