4. Background Information

Data records accumulated over the past 100 years indicate that sea levels have been rising at a rate of 1-2 mm/yr due to the thermal expansion of the ocean and the increased melting of continental and alpine glaciers (Houghton et al. 1996). During the next 100 years, increasing atmospheric concentrations of CO2 and other greenhouse gases may lead to an increase in the world's mean surface air temperature of 1-5°C unless emission levels are reduced (Houghton et al. 1996 and Warrick et al. 1993). Such warming could further enhance the thermal expansion of the ocean and the melting of continental and alpine glaciers.

Changes in climate will affect the coastal zone. Short-term climatic variations have been shown to affect the maximum intensity and frequency of storms (Emanuel 1988) and can cause an acceleration or deceleration in shoreline erosion rates (Dolan et al. 1988). Unanticipated changes in these factors can result in unnecessary loss of life and/or property (Case and Mayfield, 1990). This database may be used to identify areas that are, or could be, at risk to erosion or inundation from change in climate or sea-level rise based on information on the past and current state of the coast.

In 1987, the U.S. Department of Energy's Atmospheric and Climate Research Division funded Dr. Vivien M. Gornitz (Goddard Institute for Space Studies) and the Carbon Dioxide Information and Analysis Research Program (CDIARP), Resource Analysis Project, at Oak Ridge National Laboratory (ORNL) in Oak Ridge, Tennessee, to develop a Coastal Hazards Data Base to provide information on the past and current state of world coastlines. The data base contains information on relative sea-level trends, elevation, vertical land movements, horizontal displacement (erosion/accretion), coastal geomorphology, and geology (Gornitz and Kanciruk 1989). CDIAC has published the following three volume series of NDPs for the continental United States: A Coastal Hazards Data Base for the U.S. East Coast, ORNL/CDIAC-45, NDP-043A; followed by A Coastal Hazards Data Base for the U.S. Gulf Coast, ORNL/CDIAC-60, NDP-043B; and finally this NDP for the U.S. West Coast (ORNL/CDIAC-81, NDP-043C) (Gornitz and White 1992, Gornitz and White 1994, and this volume). A complementary coastal data base for Canada has been developed by the Geological Survey of Canada and is described in Shaw et al. (1994).

The data in this NDP may be used to calculate the relative vulnerabilities of different areas along the U.S. West Coast to projected increases in air and sea surface temperatures and sea-level change. This data base may also be combined with the two previous coastal hazard NDPs (NDP-043A and NDP-043B) to obtain a data base that covers the entire conterminous United States. This information will be useful to researchers, government planning agencies, the private sector, and educational institutions interested in determining the present and future vulnerabilities of coastal zones to erosion and sea-level rise.

The data base described here comprises data extracted from a variety of sources, including publications of the National Oceanic and Atmospheric Administration (NOAA), the U.S. Army Corp of Engineers, the U.S. Geological Survey (USGS), universities, and other federal and state agencies. These data varied in scale and format. To facilitate data analysis, these data have been referenced to a grid of 0.25° latitude by 0.25° longitude and to a 1:2,000,000 digitized coastline of the U.S. West. This NDP defines the U.S. West Coast as extending from the California-Mexican border to the Washington-Canadian border (Fig. 1).