The Hoko River Watershed is large, with about 25 miles of mainstem and about 80 additional linear miles of tributaries. It originates in the foothills of the Olympic Mountains, and drains a steep, incised landscape that has been extensively logged and roaded. The lower 10 miles of the Hoko mainstem flow through a moderately sloped terrain, with a low gradient and plentiful gravel. Rainfall on the Hoko is abundant. The estuary extends into the river for more than a mile. The Little Hoko River is the major tributary in the lower basin, and joins the Hoko at RM 3.5. The Little Hoko flows through a moderately steep terrain. Downstream of RM 3.5, the Little Hoko has a low gradient as it flows through a flat valley to its confluence with the Hoko. Historically, the Hoko basin was a coniferous forest with a few patches of red alder. About 95% of the old growth has been converted into commercially managed tree farms, and nearly all of the basin has been harvested at least once down to the streambanks. Riparian forests are now dominated by red alder. Channels are chronically depleted of large woody debris. The Hoko drainage is greatly impacted by dense riparian roads, with hundreds of separate landslides associated with logging and clearcuts since the 1950s. About 500 acres along the lower mainstem Hoko is non-forest and in agricultural use. The Lower Hoko contains several hundred acres of non-forested state park land, which is managed for wildlife and human uses. Along the mainstem, a railroad grade extensively impacts the floodplain, contributing sediment and constricting the channel. In spite of this, the Hoko River contains abundant spawning and potentially high quality rearing habitat. The Little Hoko has been channelized and diked in the lower two miles, contributing to downcutting and scouring problems. Water withdrawals serving several communities impact summer flows in this basin with naturally low stream flows. A 1.2 million dollar restoration project was completed between 1994-98, and the results are currently being assessed. The estuary has been altered by forest practices, yet eelgrass is present and provides fish habitat at the river mouth.
The Hoko mainstem and Little Hoko both support chinook, chum, coho, and winter steelhead. Low summer flows impact upstream migration and spawning, especially for fall chinook and sometimes coho salmon. Summer temperatures have been recorded above state standards in the Little Hoko River, due to conversion impacts. Salmon need cold temperatures and lots of dissolved oxygen to thrive, and these poor conditions will add to the stress caused by other environmental factors in these systems. Fine sediment in streams fills up the "interstitial" spaces between the gravel that fish need for spawning and feeding, and therefore negatively impacts the survival success of salmon. Over 48 miles of suitable spawning habitat exist for fall coho on the Hoko.
- State of the Waters of Clallam County 2004