Erosion Control Toolbox: Preserve Existing Vegetation


Preserve existing vegetation

Photo Showing the Preserving of Existing Vegetation: Preserving existing vegetation involves minimizing disturbance to and/or avoiding existing site vegetation during construction of a transportation project. Vegetation is typically preserved by including a specification that directs the Contractor to avoid disturbance of specific areas, and/or to install temporary fencing to protect the vegetation. Preserving healthy existing site vegetation is more effective at maintaining stormwater quality than removing and planting new vegetation.

When to Use This Treatment

  • Use on all projects that include existing native or non-native vegetation to be protected and preserved, which can be beneficial for wetlands, floodplains, streams, environmentally sensitive areas, steep slopes, and other areas where erosion control may be difficult to establish, install or maintain.


  • Most effective method to maintain water quality, and minimize runoff volume and velocity
  • Does not require establishment of new vegetation for erosion control
  • Increased filtration capacity than newly planted vegetation from existing root structure
  • Reduced stormwater discharge with greater interception and evapotranspiration
  • Provides wildlife habitat and aesthetic value
  • Potential for reduced maintenance than newly planted vegetation


  • Preservation of existing vegetation may not be possible due to the earthwork required to construct the project
  • Potentially requires increased effort in design and construction management to maintain elements intended to minimize impacts to existing vegetation

Standard Specifications

  • Refer to Standard Specifications, Section 14, Environmental Stewardship
  • Refer to Standard Specifications, Section 16, Temporary Facilities


  • See Caltrans Standard Plan for Temporary Water Pollution Control Details (Temporary High-Visibility Fence)

Estimate Information

  • Use Bid Item Code 160110 Temporary High-Visibility Fence to specify fencing to protect existing site vegetation



Updated: November 29, 2022