Assessing Riverbank Erosion and Land Cover Changes in Permafrost Regions Based on a Terrain Analysis Approach: An Example from the Colville River Delta, Northern Alaska

摘要

Arctic deltas are dynamic and complex environments influenced by the presence of permafrost and affected by a wide range of processes. Erosion may directly impact communities and local ecosystems, while there may be consequences at the global scale such as the release of greenhouse gases. Channel migration and erosion must also be considered in the routing and design of linear infrastructure, including pipelines, roads, and bridges built for oil and gas development on the North Slope of Alaska. Assessing channel migration and erosion helps evaluate future changes, while cryofacies and terrain analysis approaches allow estimation of ground properties over extended areas. We studied erosion rates, and ground loss (areas, volumes) by terrain unit along a major distributary in the Colville River Delta (Alaska), the Nigliq Channel, from 1948 to 2013. We integrated an analysis of digital elevation models with a channel migration analysis and available data on local terrain units and subsurface conditions. The long-term maximum erosion rates from 1948 to 2013 averaged 0.9 m y~(-1) and ranged from 0.4 to 3.3 m y~(-1). The inactive- and active-floodplain cover deposits experienced the highest erosion (269,960 m~2 and 150,830 m~2, respectively); however, the alluvial terrace in the Gubik Formation had the largest ground loss volume due to banks being over twice higher, on average. Eroding the older ice-rich terrain units forming the floodplain toposequence, such as the inactive-floodplain cover deposits, resulted in ground loss volumes of about 208,357 m~3 as soil solids and about 833,429 m~3 as ground ice. Our study supports the pertinence to integrate terrain analysis and cryofacies approaches in erosion assessment at the landscape scale along a permafrost-influenced deltaic channel.