Alaska Climate Change Impact Mitigation Program

Hazard Impact Assessments: Nelson Lagoon

Nelson Lagoon was awarded a $50,000 State Fiscal Year 2011 Hazard Impact Assessment grant to identify and define the climate change-related hazards in Nelson Lagoon, establish current and predicted impacts, and provide recommendations on alternatives to mitigate the hazard impacts.

Background

Nelson Lagoon is located on the northern coast of the Alaska Peninsula, on a narrow sand spit that separates the lagoon from the Bering Sea. It is 580 miles southwest of Anchorage. Nelson Lagoon is located in the Aleutian Islands Recording District. The coastal shoreline in Nelson Lagoon is used primarily for fishing. Nelson Lagoon lies within an extensive complex of low-lying marshy coastline, tidal flats, coastal inlets, lakes and lagoons. The community is located on a sandy spit built from former beach ridges which have been partially stabilized by vegetative cover. The beaches are composed of dark sands and gravel. The area around Nelson Lagoon is treeless, low-profile tundra dominated by grass, forbs and mosses.

Nelson Lagoon lies in the maritime climate zone. Frequent and dramatic weather changes occur, with a constant prevailing wind of 20 to 25 mph. Temperatures average 25 to 50 °F, with a range from -15 to 75 °F. Annual snowfall averages 56 inches, with a total precipitation of 33 inches.

The Alaska District Corps of Engineers (USACE) conducted a Baseline Erosion Assessment and identified the issues that Nelson Lagoon is having. They noted that the erosion problems in Nelson Lagoon include coastline erosion on the Bering Sea and Nelson Lagoon side of the spit, and river erosion from the Nelson and Sapsuk Rivers. Factors causing and contributing to the erosion include high tides, storm surges, and wind and wave action. This has been acerbated by dwindling sea ice. In the past, most of Nelson Lagoon was protected by ice for part of the winter storm season, but during the past 10 to 15 years, this protection has not been present.

Historically, the beach area of Nelson Lagoon tends to wash out in one area and then rebuild in another. As the erosion continues, the spit is getting longer and narrower and the advancing erosion continues to threaten structures. The active erosion area along the Nelson Lagoon side of the spit is less than 100 feet from community structures, including housing and the airstrip. In addition, the erosion also regularly threatens the community water lines, which are often damaged during storm events and have been replaced three times in recent years. In this area during winter of 1998, a storm event resulted in the exposure of 3,000 feet of the community’s water line, which then froze. Major erosion events in the community have been constant for the last 20 years, resulting in an average of 5 feet per year of shoreline erosion. Erosion along the spit occurs at a rate of approximately 1 to 2 feet per year, The community has attempted to bury and reinforce protection of the waterline but it still presents a concern to the community. The community also installed erosion protection measures along the beach including gabions to anchor existing wood in the breakwater; and geotube containment structures, consisting of sediment-filled sleeves of geotextile fabric, however the USACE notes that the gabion project has not had very much success due to high winds and tides. The geotube project has not been in place for long enough to make a fair assessment.

A section of community water transmission line completely exposed by beach erosion. Photo: Aleutians East Borough

Nelson Lagoon main point of contact for ACCIMP Hazard Impact Assessment

Anne Bailey
Community Development Coordinator
Aleutians East Borough
Phone: 907-274-7555
Email: abailey@aeboro.org

For more information contact

Sally Russell Cox
Division of Community and Regional Affairs
Department of Commerce, Community, and Economic Development
550 West 7th Avenue, Suite 1650
Anchorage, AK 99501
Phone: (907) 269-4588
FAX: (907) 269-4066
Email:sally.cox@alaska.gov