Restoration Techniques: Bioengineering Techniques
Explore Bioengineering Techniques here by clicking on the menu bar below, or visit the Floodplains and Construction pages.

  • Overview
    Some of the frequently used bioengineering techniques include vegetated soil lifts, coir (coconut fiber) log fascines, coir wrapped logs, and sod brush trenches. Bioengineering techniques are used for a variety of purposes including: stabilizing stream banks, serving as a filter between the uplands and the river, establishing a surface for new vegetation or establishing a transition zone between land and water.
  • Benches
    Log and Cobble Benches
    Log and cobble benches are a used to help stabilize riverbanks and provide a foundation for various vegetation treatments. Different types of log and cobble benches are used for different streambank treatments. The specific treatments and bench design depend on the channel position and features. Photos 1 and 2 show log and cobble benches that have been prepared for vegetated soil lift installations. Photo 3 shows the construction of a cobble bench. The size of cobble used for the bench depends on the size of the native alluvium and on the size of potential flood events. Often the bench is backsloped and large wood is added to additionally stabilize the bank.

    After the bench is constructed a variety of bioengineering treatments are applied. Vegetative soil lifts (photo 4) are generally used on higher outside meanders, wrapped coir logs (photo 5) are typically used in riffle or run sections and sod brush trenches (photo 6) are used at transitions to deposition areas.

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  • Lifts
    Vegetated Soil Lifts
    Coir fabric and coir logs are placed on the constructed bench to form the bankline. The coir logs are then tied into the existing bankline at either end.

    The soil lifts include a woven inner fabric that helps prevent fine sediments from washing out and a heavier outer fabric that provides structural support.

    Photo 7 shows how the back bench is sloped downward to ensure that willow cuttings are placed near ground water. The structure is filled with soil to the height of the coir log (photo 8). Coir fabric is then pulled over the coir log and soil and wooden wedge stakes are placed to secure the fabric along the back edge.

    Soil and willow cuttings are placed between the lift layers and the process is repeated (photo 9 and 10). Willow cuttings are placed on the top lift and a final layer of soil is placed to the height of the bank (photo 11).

    The top layer is then seeded with a mix of native grasses and forbs. Photo 12 shows a vegetated soil lift after one growing season.

    Photo 13 shows an example of vegetated soil lifts installed to provide a vegetated buffer between the river and the high bank. The photo was taken immediately after installation. The inset photo shows the same site after three growing seasons.

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  • Fascines
    Coir Log Fascine
    Photo 14 shows the installation of coir log fascines. Coir logs are place on a constructed cobble bench and secured using duckbill earth anchors (see illustration below). Willow stakes are placed behind the logs. The second layer of coir logs is offset from the first layer and a second row of willow stakes is installed. Photo 15 shows the site immediately after installation.
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  • Trenches
    Sod Brush Trench
    Sod brush trenches add complexity and roughness to the floodplain. They are often used at areas that are transitioning from higher shear stress (e.g., outside meanders and straight sections) to depositional areas such as point bars. A trench is created (photo 16) and willow cuttings and transplanted shrubs are placed (photo 17). A coir log is placed at the bottom of the trench along the base of the willow cuttings to aid in moisture retention and to add floodplain stability (photo 18). Photo 19 shows an example of a sod mat brush trench in the first growing season.
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Kootenai Tribe of Idaho
P.O. Box 1269
Bonners Ferry, ID 83805
Phone: 208-267-3519

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