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 Smith River Project > Characteristics that Favor Ecosystem Integrity

Chapter 6 -- Changes and Trends in Stream Habitat and Fisheries (continued)

Characteristics that Favor Ecosystem Integrity

Although anadromous salmonids of the Smith River have declined, these fisheries have demonstrated greater resilience and capacity for recovery than fisheries of other rivers in the region. A combination of geologic, climatic, geographic, and political factors have resulted in low sediment loads, higher baseflows in the stream network during the summer, and general maintenance of ecological functions.

Relative to most other coastal rivers, the Smith watershed is underlain by harder parent materials and produces less fine sediment. In addition to relatively low rates of sediment production, the river system has a high capacity for sediment transport. Relative to rivers farther south, the Smith River watershed has higher rainfall and a longer rainy season. Consequently this river system has the highest runoff per area among California rivers. This results in rapid rates of sediment transport. Steep channel gradients also increase sediment transport rates. Because sediments are moved out relatively quickly, the river system recovers more rapidly from sediment inputs. Consequently, the proportion of fine sediments in stream channels in the Smith River is relatively low. The low proportion of fine sediments enhances habitat quality for anadromous salmonids and increases the resilience of these fisheries. The combination of resistant geology, steep topography, and high stream causes sediment inputs to be relatively rapidly transported downstream and out of the system. Therefore, these streams recover from sediment inputs relatively quickly, in one or two decades (McCain et al. 1995).

Most rivers in California contribute large volumes of water to agriculture and other human uses. In many rivers, diversion of water has changed the magnitude and timing of high and low flows and has contributed to the decline of native fisheries. Water from the Smith River has not been diverted into the California Water Project due to geographic factors including remote location and rugged terrain. Because there are no dams nor large scale water diversions, the annual pattern of stream flow in the Smith River is much the same as prior to European-American settlement. Because anadromous salmonids are well adapted to the natural pattern of streamflow, lack of disruption of this pattern has contributed to resilience of the fisheries.

Human activities that influence or have influenced stream habitats of the Smith River include logging and firewood cutting, road building, placer mining, hardrock mining, gravel mining, agriculture, and recreation. The designation of the Smith River National Recreation Area in 1990 has conferred an unusually high level of environmental protection on most of the watershed. Long-term recovery of aquatic systems is more likely because of recent policy changes that curtail logging and mining. In the future, sediment loads and disturbance-recovery cycles on public lands in the watershed may resemble the disturbance regime that existed prior to major human intervention. However, on private land which comprises 12.5% of the watershed, human-caused disturbances, including road building and timber harvest, are expected to continue. Environmental restrictions on activities on private land will probably increase due to the listing of the coho salmon as a threatened species under the Endangered Species Act.


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