The Sagavanirktok River, also known as the Sag River, rises between the Endicott and Philip Smith Mountains in the Brooks Range and flows north for about 180 miles (290 km) to the Beaufort Sea, roughly 105 miles (170 km) west of Kaktovik and 12 miles (19 km) northeast of Deadhorse, Alaska. Its Iñupiat name, “Sawanukto,” meaning “strong current,” was recorded in 1901 by Samuel J. Marsh, a prospector. He is credited with discovering the first oil seep in the North Slope region, specifically near Cape Simpson. The river’s delta, about 13 miles (21 km) wide, is cut by several distributaries where it meets the Beaufort Sea coast between Foggy Island Bay and Prudhoe Bay.

The Beaufort Sea coast has some of the fastest shoreline erosion rates in the world, and they appear to be increasing. A U.S. Geological Survey study of the coast found that average annual erosion rates climbed from about 20 feet a year between the mid-1950s and late 1970s to 45 feet a year between 2002 and 2007. Around Prudhoe Bay, continuous permafrost is thawing, which is accelerating both coastal and riverbank erosion. The Trans-Alaska Pipeline System and the Dalton Highway parallel the river’s course from Atigun Pass, in the Brooks Range, to Deadhorse. The highway, mostly an unpaved, two-lane gravel road, was built in 1974 to support construction of the pipeline.

Winter overflow, known as aufeis or icing, is a common feature of braided Arctic rivers like the Sagavanirktok, forming when shallow channels freeze and force water up through cracks or over the ice surface, sometimes building layers many feet thick. In late March and early April 2015, winter overflow from the Sagavanirktok River crossed the Dalton Highway near Deadhorse at several points, closing the road for 12 days while crews dug channels to redirect the water and ice back toward the river. The following month, during the spring ice breakup, flooding closed the highway again at several locations, this time for 18 days, the longest closure since the road was built and the first breakup-related flooding event of its kind. Read more here and here. Explore more of Sagavanirktok River and the Beaufort Sea here: