The species composition and structural diversity of plant communities in healthy riparian zones provide summer and winter thermal regulation, nutrient filtering, and amounts and distributions of large wood needed to sustain habitat complexity. Healthy riparian zones also help maintain appropriate rates of surface erosion, bank erosion, and channel migration. Riparian areas throughout the Northwest are generally damaged in their ability to perform these ecological functions. Flow regimes regulate the structure and stability of stream channels, the transport of organic matter that serves as habitat and food for fish, and the physical and biological connections from top to bottom in watersheds. Natural flow regimes are often critical to locally-adapted salmon stocks, whose life histories are linked to the seasonal and spatial flow patterns under which they evolved.
Floodplains have functions essential to maintaining high-quality salmon habitat.
Wetlands also provide important winter refugia and rearing habitat in some forested mountain drainage basins. Water Use and Migration Corridors 1. Managing mainstem migration corridors and tributaries by this principle will help rebuild connectivity within watersheds and among salmon habitats. It will help restore the characteristic flow regimes to which specific stocks in specific watersheds have adapted. An ecosystem approach is essential, especially in complex cases.