ABSTRACT: Hazards and risks to community infrastructure, Sachs Harbour: A contribution to Arcticnet Project 1.2.

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The community of Sachs Harbour has expressed concern over the impact of climate change on coastal erosion, and consequently was chosen fordetailed study. Fieldwork and analyses of remote sensing images were used to assess coastal processes, rates of coastal retreat, and decadal changes in coastal erosion rates. The southwestern coastline of Banks Island is dominated by low bluffs composed of unlithified glacial sediments containingsegregated ice lenses and ice-rich silty sand horizons. Community planning in Sachs Harbour requires adequate space for new and replacement housing. The hillside location of the community makes planning for housing and infrastructure difficult. Several dwellings have been abandoned and are scheduled for demolition due to their age and proximity to the coastline, as retreating bluffs and permafrost ablation have generated concern within thecommunity. Most coastal cliffs within the community have not shown retreat over successive coastal surveys. However, the eastern slopes in the community, and those east and west of the community boundary show evidence of gullying and potential for retreat in the future. These areas are therefore unsuitable for community expansion. Gullying and slope movementalong roads and culverts are important concerns for the community in determining expansion locations. The community is protected from wave actiondue to storm events. Mechanical erosion from wave action during events does not pose a great risk to infrastructure within the community, as infrastructure is not directly adjacent to the coastal zone. Coastal retreat within the community is due to thermal erosion, combined with longshore transport of material towardsthe east removing slumped material from the waterline. Along the southwestern coastline of Banks Island, some areas have higher sensitivities than others based on shoreline displacement, relief, wave height and geology. West of Martha Point, high concentrations of ground ice present within thesediments, retreat rates of approximately 3 m/a in coastal bluffs and an area directly open to wave attack indicate that this location is highly sensitive to sealevel rise. The Sachs lowlands are also highly susceptible to sea level rise, based on shoreline displacement of approximately 1.5 m/a, high ground ice contents in fine grained material, and beaches less than 3 m wide directly exposed to wave action and sea ice. Although thermal erosion and storm events are not a major concern for infrastructure in the community at present, rising sea level, decreased sea ice and the increased effectiveness of storm events may lead to increased thermal and mechanical erosion along coastal bluffs and increased runoff along slopes within the community. An increase instorm events in the future combined with lesser sea ice in the Amundsen Gulf will increase the effectiveness of storms to impact the coastline. This could cause undercutting of bluffs, block failure, increased runoff leading to suspension and loss of sediment into the nearshore. With warming temperatures, decreased sea ice and increased storm events, rates of coastal retreat will likely increase.

Bibliography of Canadian Geomorphology