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Northern Alaska Coastal Erosion Threatens Habitat and Infrastructure
In a new study published July 2015, scientists from the U.S. Geological Survey (USGS) found that the remote northern Alaska coast has some of the highest shoreline-erosion rates in the nation. Analyzing more than half a century of shoreline-change data, scientists discovered that the pattern is extremely variable, with most of the coast retreating at rates of more than 1 meter per year.
"Coastal erosion along the Arctic coast of Alaska is threatening Native Alaskan villages, sensitive ecosystems, energy- and defense-related infrastructure, and large tracts of Native Alaskan, State, and Federally managed land," said Suzette Kimball, acting director of the USGS.
Scientists studied more than 1,600 kilometers of the Alaskan coast between the U.S.-Canadian border and Icy Cape, Alaska, and found that the average rate of shoreline change, taking into account beaches that are both eroding and expanding, was a loss of 1.4 meters per year. Of those beaches that are eroding, the most extreme case exceeded 18.6 meters per year.
"This report provides invaluable objective data to help Native communities, scientists, and land managers understand natural changes and human impacts on the Alaskan coast," said Ann Gibbs, USGS geologist and lead author of the new report.
Coastlines change in response to a variety of factors, including changes in the amount of available sediment, storm impacts, sea-level rise, and human activities. How much a coast erodes or expands in any given location is due to some combination of these factors, which vary from place to place.
"There is increasing need for this kind of comprehensive assessment in all coastal environments to guide managed response to sea-level rise and storm impacts," said Bruce Richmond, USGS research geologist and coauthor of the new report. "It is very difficult to predict what may happen in the future without a solid understanding of what has happened in the past. Comprehensive regional studies such as this are an important tool to better understand coastal change."
The recent study is part of the National Assessment of Coastal Change Hazards, a USGS project that combines observation and modeling of the nation's shorelines to help identify areas most vulnerable to diverse coastal change hazards, including beach and dune erosion, long-term shoreline change, and sea-level rise.
Compared with other coastal areas of the United States, where typically four or more historical shoreline data sets are available, generally back to the mid-1800s, shoreline data for the coast of Alaska are limited. The researchers used two historical data sources, from the 1940s and 2000s, which include maps and aerial photographs, as well as modern sources, such as elevation data from lidar ("light detection and ranging"). Combining the historical and modern data, the researchers calculated shoreline change at nearly 27,000 locations.
There is no widely accepted standard for analyzing shoreline change. One impetus behind the National Assessment of Coastal Change Hazards project was to develop a standardized method of measuring changes in shoreline position that is consistent on all coasts of the country. The goal was to facilitate the process of periodically and systematically updating the results in a consistent manner.
The new report, titled "National Assessment of Shoreline Change: Historical Shoreline Change Along the North Coast of Alaska, U.S.-Canadian Border to Icy Cape"), is the eighth report on Long-Term Coastal Change produced as part of the USGS National Assessment of Coastal Change Hazards project. A comprehensive database of digital vector shorelines and rates of shoreline change for Alaska from the U.S.-Canadian border to Icy Cape is presented along with this report. Data for all eight long-term coastal change reports are also available on the USGS Coastal Change Hazards Portal.
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