Climate Change Vulnerability and Risk Assessment for an "At-Risk" Community

Shaktoolik, Alaska, is a remote village of 260 people, located 125 miles east of Nome, on a narrow spit of land between the Tagoomenik River and the Bering Sea. Brightly painted houses line either side of the village’s only road, a 1-mile stretch of sand and gravel.

Because the village is in an area prone to storms and winds, this is the small community’s third location, and they may need to move again. The current location is threatened by flooding, which results in inundation of the spit from both sides, and erosion of the land from storm surges, which damage buildings, homes, and infrastructure.

The Alaska Department of Environmental Conservation’s Immediate Action Work Group included Shaktoolik in the six top-priority communities considered to be “at-risk” to the impacts of climate change, and effects of global warming, including rising sea levels. In 2009, the United States Government Accountability Office considered Shaktoolik to be one of four communities in immediate need of relocation.

For the community and other key stakeholders to evaluate climate change adaptation options, Golder, a member of WSP, teamed with Bristol Engineering Services Company, an Alaskan Native Corporation, to provide a climate change vulnerability and risk assessment. The primary focus of our work was to quantitatively assess the community’s vulnerability to flooding and erosion, and to consider the climate change mechanisms that can adversely impact this risk.

Using information from historical events, climate change inputs (such as sea level rise, ice cover and wind condition changes), we used a unique multi-layered approach to quantify hazards. This included applying Monte Carlo Method analysis of tides and storm surges, combined with two-dimensional wave modelling and associated runup and overtopping discharge modelling, for a range of existing and future scenarios.

Coastal flooding and erosion modelling results were converted to consequence and likelihood ratings, to estimate risk under current and future climate conditions. This required the development of consequence and likelihood scales for which significant buildings and infrastructure were ranked. The advantage of using this type of matrix is that changes to both likelihood and consequence and their impact on risk can be shown.

Community engagement sessions provided an opportunity to provide updates and seek feedback on progress and methods, summarize preliminary study results, and gather essential input from community members on critical infrastructure and perceptions of community vulnerability during past and future events. While these were scheduled to be in person sessions, the onset of the coronavirus pandemic (COVID-19) necessitated an alternative approach involving remote teleconference calls with Shaktoolik elders and knowledgeable persons.

The input and feedback provided by the community during the engagement sessions was vitally important to the study and its outcomes. It was an opportunity to discuss flooding, erosion, climate and sea ice trends and changes as well as providing the chance to gather area-wide, site-specific, and human context regarding the physical environment hazard and vulnerability setting.

The findings from the risk assessment showed that consequence and risk to community infrastructure from flooding is expected to increase with climate change. It was found that many of the risks to significant buildings and infrastructure for the community are manageable but will require adaptation strategies to cope with risk under current climate conditions.

The study provided guidance regarding the relative severity of current versus future risk, and an indication of the timeline associated with when “management in place” is likely to become unsustainable. By 2050, the amount of adaptation needed increases, for which the costs will need to be assessed. By the end of the century, Shaktoolik may be exposed to climate risks that are unmanageable due to relatively frequent inundation of significant buildings and infrastructure.

The findings and conclusions of our work will be used by the community and other key stakeholders to evaluate climate change adaptation options for the village. As the need for increasing adaptation increases, costs associated with management in place will need to be assessed relative to the costs of relocation.

This important assessment gives the community a time horizon in which to prioritize short-term mitigation activities regarding implementation of erosion and flood protection for critical infrastructure, as well as the ability to plan for the future when erosion and flood protection is no longer sustainable.

At the time of the project, work was contracted to Golder, which was later acquired by WSP.