Reconnaissance observations were made along the Beaufort Sea coast of Alaska in 1970 during a 4-week period after initiation of river flow into the ice-covered ocean. During the first few days following river breakup, the fast ice was inundated by fresh-water overflow for as far as 10 km from shore. The water drained through widely distributed drain holes (strudel) in the ice creating scour depressions in the sea bottom. Later the rivers flowed directly into growing open-water areas surrounding distributary mouths and thence seaward below the fast ice. The presence of the sea ice during river flood greatly restricts the cross-sectional area available for the seaward flow out to at least the 2-m contour, where the bottom slope suddenly steepens. At the Colville Delta, the 2-m bench extends 5 to 8 km from shore and presumably represents an area of sediment bypassing. It appears that only insignificant amounts of sediment are rafted away from arctic Alaska's deltas during the final breakup of the sea ice.

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