Stephen P. Leatherman

Global Warming and Coastal Erosion

One of the most certain consequences of global warming is an increase of global (eustatic) sea level. The resulting inundation from rising seas will heavily impact low-lying areas; at least 100 million persons live within one meter of mean sea level and are at increased risk in the coming decades. The very existence of some island states and deltaic coasts is threatened by sea level rise. An additional threat affecting some of the most heavily developed and economically valuable real estate will come from an exacerbation of sandy beach erosion. As the beach is lost, fixed structures nearby are increasingly exposed to the direct impact of storm waves, and will ultimately be damaged or destroyed unless expensive protective measures are taken. It has long been speculated that the underlying rate of long-term sandy beach erosion is two orders of magnitude greater than the rate of rise of sea level, so that any significant increase of sea level has dire consequences for coastal inhabitants. We present in this paper an analytical treatment that indicates there is a highly multiplicative association between long-term sandy beach erosion and sea level rise, and use a large and consistent data base of shoreline position field data to show that there is reasonable quantitative agreement with observations of 19th and 20th century sea levels and coastal erosion. This result means that the already-severe coastal erosion problems witnessed in the 20th century will be exacerbated in the 21st century under plausible global warming scenarios.

Greenhouse Effect and Sea Level Rise: The Cost of Holding Back the Sea

Abstract Previous studies suggest that the expected global warming from the greenhouse effect could raise sea level 50 to 200 cm (2 to 7 ft) in the next century. This article presents the first nationwide assessment of the primary impacts of such a rise on the United States: (1) the cost of protecting ocean resort communities by pumping sand onto beaches and gradually raising barrier islands in place; (2) the cost of protecting developed areas along sheltered waters through the use of levees (dikes) and bulkheads; and (3) the loss of coastal wetlands and undeveloped lowlands. The total cost for a 1‐m rise would be between

Twentieth-Century Storm Activity along the U.S. East Coast

270 and

Sea level rise shown to drive coastal erosion

475 billion, ignoring future development. We estimate that if no measures are taken to hold back the sea, a 1‐m rise in sea level would inundate 30,000 sq km (14,000 sq mi), with wet and dry land each accounting for about half the loss. The 1500 sq km (600–700 sq mi) of densely developed coastal lowlands could be protected for approximately

Migration of Assateague Island, Maryland, by inlet and overwash processes

1000 to

Quantification of Beach Changes Caused by Hurricane Floyd Along Florida's Atlantic Coast Using Airborne Laser Surveys

2000 per year for a typical...

Do Storms Cause Long-Term Beach Erosion along the U.S. East Barrier Coast?

Abstract It has been speculated that future global warming will change the frequency and severity of tropical and extratropical storms. The U.S. east coast is heavily impacted by such storms, so it is important to determine their natural temporal variability for the last century during which global warming has been relatively small. Storm surge data obtained from hourly tide gauge records provide a unique quantitative measure of storm duration and intensity, unlike qualitative estimates based on eyewitness reports or meteorological hindcasts. To demonstrate the potential of storm surge data for climate analysis, the authors have evaluated 10 very long records of water level anomalies. An analysis of the hourly tide gauge records along the U.S. east coast shows a considerable interdecadal variation but no discernible long-term trend in the number and intensity of moderate and severe coastal storms during this century. However, sea level rise over the last century has exacerbated the damage to fixed structu...

Beach Rating: A Methodological Approach

Our research has shown that an important relationship exists between sea level rise and sandy beach erosion. The link is highly multiplicative, with the long-term shoreline retreat rate averaging about 150 times that of sea level rise. For example, a sustained rise of 10 cm in sea level could result in 15 m of shoreline erosion. Such an amount is more than an order of magnitude greater than would be expected from a simple response to sea level rise through inundation of the shoreline. Sea level is certainly only one of many factors causing long-term beach change. Shoreline revisions from inlet dynamics and coastal engineering projects are more pronounced in most areas of the US. east coast and tend to mask the effect of a rise in sea level even over extended intervals. The implication is that sea level rise is a secondary but inexorable cause of beach erosion in such areas.

Mapping Shoreline Position Using Airborne Laser Altimetry

The northern part of Assateague Island, Maryland, has a history of rapid shoreline erosion, with washovers much in evidence. A comparison of aerial photography shows that the greatest island widths and highest rates of landward migration are associated with inlet dynamics. The over-wash process, at maximum transport conditions in this sand-starved area, is effective only in maintaining the island as a low, narrow barrier.

Recreational impacts on the distribution of ghost crabs Ocypode quadrata fab.

Abstract Quantitative data on beach changes caused by coastal storms is critical to the understanding of coastal morphodynamics and mitigation of coastal erosion hazards. Recent advances in airborne LIDAR technology allow large-scale mapping of beach erosion, dune scarping, and overwash deposition with incredible detail. By comparing 40 km of beaches along the central Florida Atlantic coast surveyed before and after Hurricane Floyd in 1999, we found that most beaches experienced erosion; about −18 to +1 m3/m of sediment per unit shoreline length were removed or deposited. Beach erosion is not spatially uniform, and variations in magnitude occur three dimensionally. The high-density LIDAR data provided accurate information about shore changes both at small and large scales.