Trees along streams create shade that helps maintain low water temperature. Cool water is an important component of fish habitat, especially for fish like salmon, steelhead, and trout that travel up streams and creeks to reproduce.

Fallen logs in the water create complex stream structures that provide safety and refuge for adolescent fish. Leaves and debris from streamside plants are a source of food for many aquatic organisms.

The roots of trees and shrubs hold soil in place, helping to prevent erosion. Roots also absorb excess nutrients that run off of lawns or agricultural fields. Microorganisms living in the soil of streamside buffers are effective at breaking down toxins in herbicides and other chemicals.

Robust streamside plantings help reduce the chance of flooding during periods of heavy rain. Rainwater moving across the land is slowed considerably when it reaches dense vegetation. Slowing the flow of water allows more time for soil and plants to absorb rainwater.