James G. Titus: Potential Effects of Global Climate Change on the United States, Report to Congress, Chapter 7, Sea Level Rise

Potential Effects of Global Climate Change on the United States

Chapter 7. Sea Level Rise

by James G. Titus

Findings
Global warming could cause sea level to rise 0.5 to 2 meters by 2100. Such a rise would inundate wetlands and lowlands, erode beaches, exacerbate coastal flooding, and increase the salinity of estuaries and aquifers.
• A 1-meter rise could drown approximately 25 to 80% of the U.S. coastal wetlands; ability to survive would depend largely on whether they could migrate inland or whether levees and bulkheads blocked their migration. Even current sea level trends threaten the wetlands of Louisiana.
• A 1-meter rise could inundate 5,000 to 10,000 square miles of dryland if shores were not protected  and 4,000 to 9,000 square miles of dryland if only developed areas were protected.
• Most coastal barrier island communities would probably respond to sea level rise by raising land with sand pumped from offshore. Wide and heavily urbanized islands may use levees, while communities on lightly developed islands may adjust to a gradual landward migration of the islands.
• Protecting developed areas against such inundation and erosion by building bulkheads and levees, pumping sand, and raising barrier islands could cost $73 to $111 billion (cumulative capital costs in 1985 dollars) for a 1-meter rise by the year 2100 (compared with $6 to $11 billion under current sea level trends).  Of this total, $50 to $75 billion would be spent (cumulative capital costs in 1985 dollars) to elevate beaches, houses, land, and roadways by the year 2100 to protect barrier islands (compared with $4 billion under current trends). Developed barrier islands would likely be protected from sea level rise because of their high property values.
• The Southeast would bear approximately 90% of the land loss and 66% of the shore protection costs.

Policy Implications

• Many of the necessary responses to sea level rise, such as rebuilding ports, constructing levees, and pumping sand onto beaches, need not be implemented until the rise is imminent. On the other hand, the cost of incorporating sea level rise into a wide variety of engineering and land use decisions would be negligible compared with the costs of not responding until sea level rises.
• Many wetland ecosystems are likely to survive sea level rise only if appropriate measures are implemented in the near future. At the state and local levels, these measures include land use planning, regulation, and redefinitions of property rights. The State of Maine has already issued regulations to
enable wetlands to migrate landward by requiring that structures be removed as sea level rises.
• The coastal wetlands protected under Section 404 of the Clean Water Act will gradually be inundated. The act does not authorize measures to ensure survival of wetland ecosystems as sea level rises.
• The National Flood Insurance Program may wish to consider the implications of sea level rise on its future liabilities. A recent HUD authorization act requires this program to purchase property threatened with erosion. The act may imply a commitment by the federal government to compensate property owners for losses due to sea level rise.
• The need to take action is particularly urgent in coastal Louisiana, which is already losing 100
square kilometers per year.


Much more at this link:  http://www.epa.gov/climatechange/effects/downloads/rtc_sealevelrise.pdf