Stream Bank Erosion
Rivers and streams are not fixed landscape features. Over time, their banks shift and move throughout a wider area called the floodplain, which results in natural erosion. The effects of this erosion can be very subtle over a long period of time, or very dramatic during flood events.
Erosion along a streambank can also result from human land use and associated infrastructure. Land use and infrastructure often has a ripple effect on natural forces within a watershed. For example, land use that decreases the retention of water in streamside soils (such as removing nearby vegetation) can increase the overall velocity of water flowing from the upper portions of a watershed to the lower areas. Increased velocity can cause stream bed downcutting, which leaves banks vulnerable to erosion. Human activity along a stream can compromise the natural buffer zone of a river, called the riparian zone, which in turn increases the rate of erosion. Unchecked erosion like that often seen in heavily disturbed riparian zones can result in decreased water quality that negatively affects aquatic life, as well as municipal drinking water sources. In severe cases, property loss may be incurred as land simply breaks loose into the water to be swept downstream, possibly taking manmade structures with it.
Assessing the underlying causes of erosion is important before taking action to address the concern. If watershed-level downcutting is causing your streambank to become too steep for vegetation grow and remain established, there is often little a landowner can do to protect a streamside home other than extremely expensive and often only temporary fixes. If, however, the erosion is primarily due to human activity in the riparian zone, like cutting down vegetation for a better view or allowing livestock access along long portions of a stream, conservation practices and restoration efforts can often restore the function that riparian zones provide. These functions include bank stabilization, water quality protection (filtration and shade), and fish and wildlife habitat. This function is provided primarily through the establishment of appropriately adapted native, perennial vegetation.
Soil bioengineering is a solution that can address moderate to localized streambank erosion depending upon the scale of erosion present. The general concept relies upon restoring strongly rooted, woody vegetation. Woody vegetation protects streambanks in several ways:
Erosion along a streambank can also result from human land use and associated infrastructure. Land use and infrastructure often has a ripple effect on natural forces within a watershed. For example, land use that decreases the retention of water in streamside soils (such as removing nearby vegetation) can increase the overall velocity of water flowing from the upper portions of a watershed to the lower areas. Increased velocity can cause stream bed downcutting, which leaves banks vulnerable to erosion. Human activity along a stream can compromise the natural buffer zone of a river, called the riparian zone, which in turn increases the rate of erosion. Unchecked erosion like that often seen in heavily disturbed riparian zones can result in decreased water quality that negatively affects aquatic life, as well as municipal drinking water sources. In severe cases, property loss may be incurred as land simply breaks loose into the water to be swept downstream, possibly taking manmade structures with it.
Assessing the underlying causes of erosion is important before taking action to address the concern. If watershed-level downcutting is causing your streambank to become too steep for vegetation grow and remain established, there is often little a landowner can do to protect a streamside home other than extremely expensive and often only temporary fixes. If, however, the erosion is primarily due to human activity in the riparian zone, like cutting down vegetation for a better view or allowing livestock access along long portions of a stream, conservation practices and restoration efforts can often restore the function that riparian zones provide. These functions include bank stabilization, water quality protection (filtration and shade), and fish and wildlife habitat. This function is provided primarily through the establishment of appropriately adapted native, perennial vegetation.
Soil bioengineering is a solution that can address moderate to localized streambank erosion depending upon the scale of erosion present. The general concept relies upon restoring strongly rooted, woody vegetation. Woody vegetation protects streambanks in several ways:
- Root systems help hold the soil particles together increasing bank stability.
- Vegetation creates a rougher surface that can dissipate energy and increase erosion resistance from adjacent stream flow along the bank.
- Vegetation acts as a buffer against the hydraulic forces and abrasive effect of transported materials.
- Dense vegetation on streambanks can induce sediment deposition and build banks.
- Vegetation can redirect flow away from the bank naturally.
- Unlike rock, which transfers stream energy downstream, dense vegetation can dampen this force reducing erosion downstream.
Download the following document to get familar with techniques that can be used for bioengineering. Please consult Lincoln SWCD, the Oregon Department of State Lands, or a professional before excavating (removing) or adding (filling) rock, soil or any other material in a stream or along the streambank. This activity is regulated by the State of Oregon and can result in fines if done without a proper permit
Lincoln SWCD is available to help with erosion concerns by providing technical assistance to landowners in Lincoln County.
Lincoln SWCD is available to help with erosion concerns by providing technical assistance to landowners in Lincoln County.
| Soil Bioengineering Techniques |
