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Sea-Level Rise and U.S. Coasts: Science and Policy Considerations

Peter Folger and Nicole Carter

CRS Report RM44632

Although the extent of future sea-level rise remains uncertain, sea-level rise generally is anticipated to have a range of economic, social, and environmental effects on U.S. coasts. Global sea level is rising due to warming and expanding oceans, melting glaciers, and melting ice sheets in Greenland and Antarctica, among other reasons. From 1901 to 2010, global sea levels rose an estimated 187 millimeters (mm; 7.4 inches), averaging a 1.7 mm rise annually; estimates are that from 1992 to 2010, the rate increased to 3.2 mm annually.
The rates of relative sea-level rise at specific locations are likely more important to coastal communities and coastal ecosystems than the global sea-level average trends.
Sea levels are rising between 9 mm and 12 mm per year (0.4 inches to 0.5 inches per year) along the Mississippi delta near New Orleans and between 1 mm and 2 mm (0.04 inches and 0.08 inches, or less) per year along some coastal shorelines in Oregon and Washington. Since the beginning of the 20th century, coastal and tidal areas have seen significant population growth and associated development and infrastructure investments. The consequences of sea-level rise are of interest not only because of the local impacts on coastal communities and ecosystems but also because of the direct and indirect impacts and risks for the federal government.
Following an introduction to sea-level rise issues , the report is divided into three primary parts:
Part I describes the phenomenon of sea-level rise. It introduces key terminology, measurements, trends, and causes.
Part II describes the types of effects that sea-level rise can have on U.S. coasts. It addresses effects on shorelines and coastal ecosystems and on coastal development and society. Part II describes federal actions to address sea-level rise and the tension between the federal role and actions taken by state, local, and private stakeholders.
Part III provides a primer on policy considerations. It raises considerations and questions associated with policies to address the causes and effects of sea-level rise. It also discusses federalism issues and general considerations associated with sea-level rise policies and investments.