Deflecting Flow

Flowing water eats away at the soil on the lower bank along the outside curves of rivers. The water is piled against the outside of the curve as the river bends, similar to the sensation of being pushed to the outside of a fast-turning car. This flowing water scours material away, causing the bank to collapse. A common and effective method of preventing erosion is to armor the bank with a robust layer of material that cannot easily be moved or washed away by the current, such as rock. This results in a bank armored against erosion, but it does not allow vegetation to flourish on the part of the bank covered in rock. It also doesn't help dissipate the energy of that flowing water, which can then be exacerbated downstream. It often requires the entire armored length to be clear-cut and graded. 

An alternative to armoring is to redirect the river's flow from the outer bank, thereby preventing scour through deflection. An effective way to do this is to angle rock barbs or weirs upstream into the channel. This forces the water to flow around and over at a perpendicular angle. This pushes the main flow back towards the center of the stream rather than along the outer bank. Often, a deep pool is made just off the end of the weir towards the center of the channel. This causes variable flows and depths within the channel that fish and other organisms like. ACD has recently implemented bendway weirs and plans to install more in the near future. For more information contact Jared Wagner, Water Resource Specialist, at This email address is being protected from spambots. You need JavaScript enabled to view it.