Erosion on the Yukon: Protecting Alakanuk’s Riverbanks

Alakanuk is a small Yupik village located on the major southern channel of the Yukon River in Alaska. Yupik for “wrong way”, Alakanuk sits amongst a maze of watercourses on a distributary of the river. In July 2021, Herrera traveled to the village to conduct an erosion assessment in response to past expansion of the main channel, threatening houses located on the water.

Changing Landscape and Tides

Over the past 70 years, changes to Alakanuk’s vegetation driven by abiotic components of the ecosystem, also referred to as allogenic succession, has led to the growth of willow and alder trees. Permafrost loss initiates the emergence of these species, providing the ideal ground conditions for tree roots to grow. Since the 1950s, locals have seen rapid alterations in Alakanuk’s landscape; transforming the once icy tundra into a more temperate domain. In addition to excessive rain, increased snowfall has insulated the ground, causing permafrost loss and increasing erosion.

River currents are also to blame for erosion along the Yukon. Currents flow fastest in areas with the lowest elevation, referred to as the thalweg. Typically located at bends in the river, the thalweg erode faster than other places, as accelerated water flow breaks down outside banks.

Alakanuk, like many Alaskan communities, has established infrastructure along the river bends with deep elevation as these areas are ideal for boats. However, areas of high boat traffic also contribute to waterline erosion, as boat wakes cause the steepening and calving of riverbanks. This leads to the widening of channels over time, further undermining infrastructure.

Changing Ways of Life

During Herrera’s visit, our team learned how Alakanuk’s changing vegetation and ground conditions impact locals and their way of life. For one, travel has become increasingly difficult across the Yukon River due to climatic changes in rainfall, snowfall, thermal ice break up, and thick, tall woody vegetation. In the past, locals have traveled atop frozen waters on sleds or snow machines. As waters begin to freeze later and melt earlier, the season to travel on top of the river shortens. Travel has also become difficult on land as upland forests block former paths.

Newfound challenges in fishing and sealing have also affected locals. Fish return on the Yukon river continues to worsen, a direct result of “ocean conditions”, a catch-all term for the ocean portion of a salmon’s life cycle. Once a popular activity amongst the Yupik population, seal hunting has also become virtually impossible as the gradual thinning of ice presents hazards for hunters.

A Silver Lining

Despite the effects of erosion on the village, there remains a silver lining. Built atop alluvium soil, Alakanuk’s infrastructure remains more stable amidst permafrost degradation. This is due to the processes of delta formation and overbank sedimentation. Additionally, new vegetation, though caused by rising temperatures, is helping deter erosion. Found primarily on eroding riverbanks, foliage from mature willow trees slows floodwaters, while their roots bind the soil together. Alakanuk’s myriad of internal resources and elder wisdom also prove useful when navigating the most feasible approaches to mitigating the effects of erosion. Herrera looks forward to further working with the community in Alakanuk to develop long-term resiliency to climate change.