The Clallam River is one of the least studied systems in the Western Strait of Juan de Fuca. Although there is limited information available for sediment levels, fairly detailed stream temperature data have been recorded. The Clallam River is about 13.4 miles long, with steep gradients in the headwaters and low gradients downstream. Forest practices have increased the Clallam River's fluvial sediment load over pristine levels. Most of the upper watershed is intact second growth managed by DNR under a landscape management plan. Logging impacts are primarily historic; the upper watershed is not currently delivering much sediment to the system. Road densities associated with logging have been too high for properly functioning habitat conditions to exist. Roads and railroad sites have a history of failure here, and mass wasting sites are the major contributors of the fines in the basin. The floodplain is bisected by a highway near RM 4.4-5.6, resulting in the loss of off-channel early juvenile rearing habitat. Water withdrawals in the watershed reduce stream flows in the river. The Clallam River estuary is an excellent nursery area for salmonids. However, human disturbance has degraded this habitat, resulting is delayed migration or blockage of spawning habitat to adult chinook. Several saltwater marshes have been filled, and sloughs and wetlands have been cut-off from their connections to the main channel. The mouth is occasionally blocked with a sandbar formation, which is a potential obstruction to anadromous salmonid access.
The Clallam River supports coho and chum salmon, and winter steelhead. 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.
- State of the Waters of Clallam County 2004