Brush Layering

Description and Function

Brush layer planting consists of live woody plant material placed into the slope face along trenches excavated along slope contours as shown in Figure 14. This technique is most applicable to areas subjected to cut or fill operations or areas that are highly disturbed and/or eroded. Layering provides the best technique to achieve soil reinforcement to resist potential shallow-seated landsliding events. Brush layers act as live fences to capture debris moving down the slope. Figure 14 below illustrates the proper steps to take when implementing the brush layering technique.


Figure 14. Brush layering.

Planning Considerations

This technique can be very disruptive to native soils and can trigger soil movements during installation. It is important to perform installation in phases and not to excavate more area than is necessary to install plant materials.

Figure 15. Brush layering detail.

If there are large quantities of loosened soils on the slope, layering is a good slope stabilization approach. Also, if imported soil material will be used to restore eroded areas, brush layering should be considered. It is best to install materials into the imported fill area and avoid disturbing existing soil structures. Use brush layering on slopes up to 1.5H:1V or in highly eroded gully areas. Plant material should be prepared as described under contour wattling except for the length of the collected material.

Limitations

Not good for dense, stiff soil structures. Not recommended as a solution to gully erosion control unless technique shown on Figure 16 is used to rehabilitate gullies.

Figure 16. Brush layering for gullies.

Advantages and Disadvantages

  • Advantages: Good immediate soil reinforcement and slope dewatering function, good erosion control capabilities for dry debris.
  • Disadvantages: Labor intensive procedure, technique is intolerant to development of water channels (rills and gullies). Therefore, use technique for appropriate site conditions.

Applicability

Compatibility

View Key to Applicability and Compatibility Graphics (Figure 2)

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