Channel erosion projections for threatened Alaska-Native communities along the Kuskokwim River

Numerous Alaska-Native (A-N) communities along the Kuskokwim River are regularly threatened by ongoing riverbank erosion, including catastrophic events. Erosion is causing the river to encroach on AN villages, threatening infrastructure and community sustainability. Current trends in precipitation and warming in the Arctic indicate that the magnitude and regularity of these events may increase. The cost-prohibitive nature of building hardening structures like seawalls means that these villages adapt to the eroding river by moving their infrastructure away from the river, a process known as managed retreat. In this study, satellite images were used to calculate riverbank migration rates near three villages of interest: Akiak, Kwethluk, and Napakiak. Annual channel boundaries from 1999 to 2016 were derived from the 30-meter resolution JRC Global Surface Water dataset. Boundaries from 2017 to the present were derived from 10-meter resolution Sentinel-2 images using the Aerial Imagery Migration Model (AIMM). Due to the improvement in resolution, estimates of channel locations from 2016 and later have higher certainty than earlier estimates. Distances between the channel boundary and 5 predefined points in each village were measured each year along 5 perpendicular transects to calculate annual migration and average migration rates. The average rates were used to project channel locations 5, 10, and 20 years into the future. Results indicate that, on average, the river migrates 9.90 m‧yr-1 towards Napakiak, 2 m‧yr-1 towards Akiak, and 1 m‧yr-1 towards Kwethluk. More than 100 buildings across the three villages may need to be moved before 2042. Erosion projection maps will be shared with key village stakeholders and could help inform future mitigation plans. As more high-resolution data becomes available, these estimates should be updated annually to reflect possible variations in river migration rates because of climate change-driven environmental change.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

thesis

Discipline thesis:degree_discipline

Geology

Department dc:contributor.department

Department of the Earth, Atmosphere, and Climate

Grantor

Iowa State University

Year dc:date.issued

2023

Author dc:creator

• Poudel, Pratik

Advisors dc:contributor.advisor

• Franz, Kristie J
• Iverson, Neal R
• Moore, Peter L

Language dc:language.iso

en

DOI

https://doi.org/10.31274/td-20240329-132

OAI identifier oai:identifier

oai:dr.lib.iastate.edu:20.500.12876/OrD8d5pr