Healthy riparian vegetation stabilizes streambanks, making them less likely to erode during high flow events; influences bank morphology; and aids in reducing streambank damage from ice, log debris, and animal trampling. The roots of trees, shrubs, and herbaceous vegetation stabilize streambanks and form overhanging banks which provide cover for aquatic species. Much of a stream’s sediment load, particularly during high flows, can be the result of bank erosion.

Schlosser and Karr (1981) found levels of suspended solids increased quickly during storm events when the streambanks were devoid of vegetation. In more stable channel sections with well-developed riparian vegetation, they found levels of suspended solids increased at a slower rate.

Vegetation along streams also reduces the velocity and therefore the erosive energy of overbank flow during floods. Riparian vegetation also provides shade, preventing excessive water temperature fluctuation that can have harmful effects upon aquatic life ranging from macroinvertebrates to fish. Vegetation affects water temperature by reducing maximum summer temperatures. This increases the water’s oxygen-carrying capacity because the higher the water’s temperature, the less oxygen it can hold. Conversely, vegetation removal can trigger an increase in water temperature that may adversely affect a stream’s biota. For example trout and steelhead require well-oxygenated water for survival; an increase in water temperature will generally reduce a stream’s population.

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