Site 10 - Pah River - Tributary

The largest tributary to the Kobuk River encountered during our trip (draining some 2000 km²), the Pah River meets its confluence with the Kobuk as an enormous mudflat with a small channel containing heavily tannic flow.The mixing line is visible for hundreds of meters and sheefish aggregations were impressive!

Physical Site Description- August 18; Noon
Pah River Confluence

• Pah River joins the Kobuk on river left of a left branch of the Kobuk, in the middle of an island complex. Across from the confluence, a newer (within the last 30 years) small cutoff channel rejoins the larger Kobuk branch.
• Across from the confluence in the Kobuk channel is a large, low elevation cobble/gravel island, with visible downstream slant in the direction of cobble deposition (downstream relative to Kobuk flow)
• Gravel island in Kobuk, across from confluence contains large woody debris
• Confluence is in the middle of the cut bank side of a large meander bend in the Kobuk’s left branch
• Upstream, the Pah follows a relatively straight, low elevation path, with small meandering sections interspersed. It originates on a marshy plateau (the Pah River Flats).
• Above the confluence, Pah rounds a large, gradual meander bend
• Large tundra plain on river left of the Pah, just upstream of confluence. First time this kind of landscape has been seen
• There is a small band of resistant Spruce vegetation river left of the Pah, near the confluence, which seems to have survived/resisted outward migration of the Kobuk’s large meander

• At the mouth of the confluence, the Pah fans out. There are mudflats extending a few hundred meters upstream (into the Pah) and across, with a small band of gravel (2-4 meters) where Pah meets Kobuk
• Mud flats contain mixture of gravel and sand. Mostly sand.
• Pah river is extremely shallow across the right side of it’s entrance into the Kobuk, with only a few inches of water for ~50m. Gets deeper on river left, but no more than ~1 meter
• Small portion of Kobuk river is flowing into the mud flats at the confluence
• Mud flats are most likely a large backwater eddy when Kobuk is high
• Large amount of Sheefish found along seam between Kobuk and Pah, over freshly deposited gravel

Location