The Environmental Leadership Program (ELP)

Stream Section 4

https://www.youtube.com/watch?v=dQw4w9WgXcQ

The Main Problem

Bank Erosion!

Bank erosion is a very common issue in streams. It can be caused by lack of vegetation to secure the sediments in place and prevent them from entering the water. It can also be caused by the water flowing against the side banks, and pushing them back slowly over time. Effective streams are cold and the main effect of erosion is an increase in temperature. The sediments entering the water cause it to become shallow and the receding banks increase the surface area. Both of these factors increase temperature.

The Rehab Strategy

Wing Deflectors and Rocks

Implementing wing deflectors helps to divert the water into a more narrow area to speed up the flow of the river. This is beneficial because it helps to oxygenate the water and keep it cool, all well keeping water from hitting the bank and causing erosion. Another solution to erosion is placing large rocks, planting vegitation and adding root wads along the edge in order to prevent the water from hitting the bank.

Secondary Issues

Steep Slopes

Steep slopes are a major issue located at the bends of streams. These 90° slopes are caused by the water constantly pushing against the bank as it turns the corner. Steep slopes are an issue because they cause erosion. Because of the steep angle, sediments are easily able to enter the water which over time, fills the stream making it more shallow. Erosion also causes the stream to widen, increasing the surface area. Both these factors cause the water temperature to increase. This is not good.

Lack of Vegitation

A lack of vegetation negatively affects the stream because vegetation is important for many different reasons. Stream side vegetation stabilizes the banks and helps keep them sturdy. Vegetation also provides cover for fish, and keeps the stream at a nice cool temperature.

Rehab Strategies

Dig bank to 45°

In order to correct these steep banks its easiest to bring in heavy machinery. Excavator's are able to easily even out the slope to a 45 degree which is the ideal slope. Adding in things like rocks, vegitation and root wads help maintain the 45 degree by preventing the water from hitting the bank directly.

Adding Vegitation

Planting dogwoods, hardwoods and other plants speeds up the natural process of succession. Having Vegetation helps prevent erosion, provides detritus and helps prevent from silt from entering stream.