California Department of Transportation

Roadside Management Toolbox

Rock Slope Protection


What is This Treatment?

Rock slope protection is the placement of rock on the surface of the soil to protect against wind and water erosion and buttress the slope against lateral movement. When used in conjunction with an underlying geosynthetic fabric, rock slope protection may also be an effective vegetation control.

When to Use This Design Concept?

RSP is recommended for slopes in natural rural and transition areas that are too steep for mowers and maintenance equipment (3:1 or greater) but should not exceed 1:1, for vegetation control purposes. Best use is from the toe of slope to the edge of any natural vegetation that is retained. To limit visual impacts RSP height should not exceed 7 m. Use of RSP in areas of concentrated runoff or in drainage facilities should be coordinated with District Hydraulics. (see California Bank and Shore Rock Slope Protection Design)


  • RSP is easy to install and repair with conventional equipment.
  • Rock color can be matched and treatment selectively vegetated to blend with context.
  • Permeon or similar stains may be applied to accelerate the appearance of weathering.
  • In some situations RSP also provides the benefit of slope armoring and buttressing.


  • RSP is typically not in context with urban or suburban areas.
  • For aesthetic purposes gravel rather than RSP is recommended for flat slopes <3:1 (see “Gravel Mulch”).

Specifications and Details

  • Standard Specifications section 72-2 Rock Slope Protection, Placement Method B


  • 20 - 80 yd2
  • BEES Item(s)
    • 721008 Rock Slope Protection (Light Method B)
    • 729010 Rock Slope Protection Fabric


Updated: May 24, 2012