 The first two of these are the only streams belonging to the Tubutulik drainage system The lower course of the river lies in a fluvial plain consisting partly of fresh-water and partly of salt-water marshes, built up by the detrital material carried by the river itself and deposited beyond its mouth in the form of mud, sand, and gravel.The river discharges into a lagoon back of a long island sand spit.This lagoon also receives at its western end the waters of Kwiniuk River.