Movement of Seabed Drifters Near the Columbia River

Seabed drifters were released on the continental shelf within 50 km of the mouth of the Columbia River to study near-bottom water and sediment movements. From June, 1966 to October, 1966, the net movement in water deeper than 55 m was northward; at lesser depths, the movement was southward and toward the coast. Drifters grounded in considerable numbers on the ocean beach within 5 km north of the north jetty of the Columbia River and also on Clatsop Spit 5 km upriver on its south bank. Relatively few were found on the ocean beach near the south jetty. The movement near shore is in agreement with that deduced for bottom water, considering the prevailing seasonal winds and waves and the intrusion of seawater into the estuary.