The main stem Satsop River is formed by the confluence of the West and East Forks.

[8][9] These rivers originate in the southern Olympic Mountains in the general vicinity of Chapel Peak, Dusk Point, and Anderson Butte.

[6][14] The Middle Fork Satsop River rises in the foothills of the Olympic Mountains and flows south, passing through steep gorges and canyons.

[3] Decker Creek flows through broad prairie lands and gently sloping valleys.

[17] The Satsop Native Americans, who lived along the river, were neighbors of the Lower Chehalis, Humptulip, and the Hoquiam peoples, with whom they shared a similar political organization.

A trail ran through the Satsop lands over which trade passed south to Grays Harbor and Willapa Bay.

Three of the Schafer brothers, sons of the pioneering family, founded one of the biggest and most successful logging companies of the area.

The plans include the elimination of excess erosion, some due to previous control attempts, as well the reintroduction of riparian habitats.

The project, planned to be completed in 2028, is meant to also increase the biome for salmon and other aquatic species while helping mitigate flood concerns in the area.

[3] The Satsop and its tributaries support a variety of migratory fish, including chinook, chum, and coho salmon.

[3] A number of projects have been undertaken to improve salmon habitat in the Satsop watershed, including the construction of spawning channels and fish hatcheries.

[3] The Satsop River's watershed is prime timber land and much of it is privately owned and regularly harvested.

The timber harvesting combined with the region's steep slopes presents erosion and mass wasting hazards.

In addition there is a relatively high density of roads, mostly for logging, which increases the erosion and sedimentation risks.

Rainfall in the region ranges from 70 to 175 inches per year, which further increases the danger of destructive erosion.