Mapping of Shallow-Water Sites to Aid Navigation on the Colville River, North Slope of Alaska

The Colville River is the largest river basin (~53,000 km
²
) in Alaskan Arctic. The residents of Nuiqsut, an established Alaska Native community of ~400 people, rely heavily on the Colville for their subsistence needs. Nonetheless, the changing river dynamics caused by accelerated bank erosion and consequent river siltation is making travel on the Colville increasingly difficult and in some cases dangerous. We used summer 2017 scenes from three optical sensors (PlanetScope, Sentinel 2, and Landsat) with resolution ranging from 3-30 m along with field measurements of water-depth to map shallow-water sites along a 45-km stretch of the Colville River. We found a strong correlation ( R
²
=0.9) between field-measured water depths and image-derived reflectance quantity (natural log ratio of green over red bands). We also analyzed a relative depth mapping technique which can be used to map shallow-water sites from optical images in the absence of field-measured water depths.