A healthy streambank is an extravagant ecosystem, the consummate source of food, shelter and of course, water, for a diverse mix of plants and animals. There are several components to a healthy streambank, starting with the riparian zone.

The riparian zone of a stream is a natural transition place from land to water, a kind of mud room before runoff enters the stream. It is ideal if it is 30 feet or wider, although narrower strips of land with a variety of vegetation can be adequate. Within healthy stream corridors, the riparian zone acts as a buffer between the damaging pollutants carried in runoff and the streamıs water. It can also help to stave off erosion. The vegetative mix in a healthy streambank can include:

Shape of Stream Channel is Important

The cross-section shape of the stream channel is important to healthy functions both within the stream and on the banks. Ideally, a U-shaped channel provides the most protection from bank erosion. This in turn keeps the water deep and cool -- ideal conditions for game fish. As the channel is distorted and widened either by erosion or channel straightening, various components of the stream habitat begin to suffer. For example, the streambed fills up, creating warmer, shallower waters. Changing the aquatic environment will eventually change the kinds of aquatic species living there. These changes usually point back to evidence of certain land uses in the adjacent watershed. Nearby urban areas with many impervious surfaces, for example, increase the velocity and amount of stormwater runoff which can erode the shape of the streambank.

Vertical or Undercut bank

This bank is optimum in terms of maintaining a healthy stream habitat. It generally rises at about a 45-degree angle or actually overhangs the stream with lush vegetation. This type of bank provides good cover for aquatic invertebrates (small animals without backbones) and fish and is resistant to erosion. However, if the bank is seriously undercut, the bank could collapse.

Steeply Sloping Bank

This bank slopes at more than a 30-degree angle and is very vulnerable to erosion. The stream channel widens as the result of erosion, pushing back the high water mark farther into new and distorted shorelines.

Gradually Sloping Bank

This type of bank slopes at 30 degrees or less. Although the shape is highly resistant to erosion, the height of the bank itself limits its streamside protection abilities.

If you're concerned about the shape or condition of your stream, contact your local Land Conservation Department. Staff will be glad to assess your stream for you. If there is a problem, there may be cost-sharing assistance to help remedy the problem.