Natural freshwater surface streams of considerable volume and a permanent or seasonal flow, moving in a definite channel toward a sea, lake, or another river; any large streams, or ones larger than brooks or creeks, such as the trunk stream and larger branches of a drainage system. [Glossary of Geology, 4th ed.]
This category is also used for rios.
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Characterization of major lithologic units underlying the lower American River using water-borne continuous resistivity profiling, Sacramento, California, June 2008

Geophysical study of the sediment under a river intended to help assess the susceptibility of this material to scour and the erosion of levees adjacent to the river.

Digital map of surficial geology, wetlands, and deepwater habitats, Coeur d'Alene river valley, Idaho

Details of materials and geologic environments in an area where a long history of mining has enriched stream sediments in silver, lead, zinc, arsenic, antimony and mercury, copper, cadmium, manganese, and iron.