It forms the first estuary south of the mouth of the Columbia River along the Oregon Coast, reaching the Pacific Ocean at Seaside in Clatsop County.

Neacoxie Creek flows in from the north, draining Clatsop Plains, the last tributary before the river enters the ocean.

Coho salmon prefer streams with a high degree of structural complexity, including the presence of large woods, flood plains, braided channels, beaver ponds, and occasionally lakes.

Anthropogenic activities, including timber harvest, mining, water withdrawals, livestock grazing, road construction, stream channelization, diking of wetlands, and urbanization have damaged this critical habitat.

[9] By using beavers to do most of the work instead of using the usual excavation and restoration techniques for wetlands mitigation, the project cost was reduced by an estimated $60,000 to $80,000.

[10] The watershed is also important habitat for Roosevelt elk (Cervus canadensis roosevelti), black tailed deer (Odocoileus hemionus), beaver (Castor canadensis), North American river otters (Lontra canadensis), northern red-legged frog (Rana aurora), and a wide range of birds, from year-round residents like great blue herons (Ardea herodias) to migrating barn and tree swallows (Hirundo rustica and Tachycineta bicolor, respectively).