Long-term rates of coastal change are shown as colored dots along the 2014 shoreline, from red to blue in meters per year, where rates are negative for erosion (loss of land) and positive for accretion (growth of the beach seaward). For example, the coast in this region has on average experienced long-term erosion at a rate of -0.9 meters per year, which is equivalent to 3.0 feet of erosion per year, appearing as yellow on the map. Indeed, most of the coastline (83%) has experienced erosion. On average, the coast has eroded back 55 meters (181 feet) from 1955 to 2014. Erosion has been most pronounced along the Elson Lagoon, at Point Barrow, and along portions of the barrier islands. Click on the colored band of dots for details at any location.
The long-term rates of coastal change were calculated from waterlines for 1955, 1979, 2002, and 2014 using the USGS Digital Shoreline Analysis System (DSAS), a well accepted approach built for use in a popular mapping software package, ArcGIS Desktop. A baseline was constructed 30 m offshore. A total of 4,977 transects were generated perpendicular to the shoreline with a spacing of typically 20 m. The long-term rate of change at each transect was calculated using a linear regression equation (the LRR statistic) that considers the position of all four shorelines (providing what is essentially an average rate for the period 1955 to 2014).
The rates of coastal change shown here were calculated with more certainty than is typical for studies in Alaska, but there are errors in the change rate to keep in mind. The average rate uncertainty for any one transect (the average LCI90 value) is +/- 0.8 m/yr (+/- 2.6 ft/yr). The uncertainty is smaller for many transects, and is much smaller when considering a stretch of coastline with hundreds of measurements. For this reason, coastal segments that are apparently stable or with uncertain rates of change are shown as gray on the map, corresponding to +/- 0.2 m/yr.
This analysis is useful for visualization of coastal change. Long-term rates may be different than experienced over shorter periods of time or in the future. The results shown here are not intended for evaluation of coastal hazards over short stretches of the coastline, but can be helpful for understanding trends of erosion or accretion experienced in the Barrow region over the last several decades.