ABSTRACT: Effects of climate change on the coastal geomorphology of southwestern Banks Island, NWT.

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Abstract

Community concern about coastal erosion led to Sachs Harbour being chosen for detailed study. Fieldwork, including RTK coastal profiling, and analyses of aerial photography and QuickBird images were used to assess coastal processes, rates of coastal retreat, and long-term decadal changes in coastal erosion rates. The southwestern coastline of Banks Island is dominated by low bluffs composed of unlithified glacial sediments containing segregated ice lenses and ice-rich silty sand horizons. Rising sea level and decreasing sea ice extent, coupled with regional submergence due to crustal flexure, has rendered this coastline vulnerable to erosion. Increasing effectiveness of storm events in eroding these bluffs has lead to increasing sedimentation on the shoreface and the nearshore. Quantification of erosion rates was accomplished by measurement of previously established transects. A total of 31 transects were surveyed, distributed from north of Cape Kellett to southeast of Sachs Harbour. Suspended particulate matter was measured in the nearshore zone and resampled during and after a small rain/wind/wave event. These results were used to determine the effectiveness of overland flow to increase sedimentation and resuspension of material in the nearshore. The coastal bluffs are undergoing retreat. Although much of the community is sheltered from wave action by a spit to the south, in the west the bluffs are exposed to higher energy conditions, and there is increased wave erosion during storm events. Thermal erosion, retrogressive thaw flow, and creep play major roles in coastal retreat. Disturbed sediment is subject to removal by wave action, although large events are necessary to transport disturbed material offshore.

Bibliography of Canadian Geomorphology