Introduction

  

Vegetation offers the best option for long-term erosion control on unstable slopes and prevents surface erosion. The protection of the slope against shallow seated landsliding is a key benefit of a revegetation program. Mixed vegetation provides cohesion of the surface soil structure of a slope. It does this by absorbing rainfall energy and preventing soil compaction from precipitation; this process is otherwise known as interception. The roots from vegetation physically bind soil particles while foliage from above ground filters sediment runoff and slow runoff velocity.

  

 
  
Vegetation can also increase infiltration of soil by maintaining soil porosity and permeability. Woody vegetation offers protection against mass movement and shallow sliding of banks. It does this by transferring the sheer stresses in the soil to the roots. Through the processes of evapotranspiration, large woody plants absorb moisture from soil, decreasing soil saturation. Large woody vegetation also acts as an anchor or buttress against abutting slopes. Though the weight of vegetation on a bank exerts a downhill force, a stabilizing force acting perpendicular to the slope is also present. Woody vegetation on a slope offers a buffer from direct wind contact on the slope reducing the risk of an unstable condition.

No amount of slope disturbance followed by replanting should replace site planning related to avoiding slope disturbances. If possible, all native vegetation should be maintained on site as well as the natural retreat of the slope crest. In addition, maintaining a greenbelt along the slope crest and limiting water onto or into the slope is rational.
In order for vegetative erosion control systems to be effective, appropriate plants tolerable to specific growing conditions must be implemented. A way of determining whether a certain plant species is appropriate depends on several factors: purpose of planting, soil permeability/drainage, available sunlight, brush competition, potential for animal damage, and elevation. The following is a general checklist for selecting slope stabilizing plants.
  • What are the specific goals and objectives for the project?
  • What are the geographic characteristics of the project site?
  • What are the climatic conditions for the project site?
  • What soil types exist in the project site and adjacent areas?
  • What is the hydrology of the project site?
  • What is the condition of the existing plant community?
  • Are there existing or planned access roads or pathways in and near the project site?
  • Do site conditions require special design considerations such as vegetation height or shape, type of root structure for erosion control, or bank stability?
  • Do present or potential hazards to the integrity of the plant community exist on-site?
  • What will be the secondary function of the project area: aesthetics, recreation, fish and wildlife habitat, sound or visual barrier, water quality protection or treatment?
  • What fish and wildlife needs are or could be provided by the plant community?
  • What plant communities are reasonable and practical given the real constraints of the project site, budget, and regulatory requirements?
  • What is the availability and cost of the desired plan species? What density of cover is desire, and in what time frame.
  • What are the short-and long-term maintenance requirements of the project site?
  • Will the recommended vegetation require special site preparation of equipment for installation?
  • Will the prescribed vegetation requirement supplemental irrigation, fertilization, or fencing to become established?
  • Given local climatic and hydrologic conditions and site constraints, when is the best time of the year for planting? Does planting need to staged over time?
  • What are the skills of the planting crew? Will training be required?