Erosion Control Toolbox

Toolbox Overview

Tools

To Combine Specifications

• Sequencing

Planning & Design

• Preserve Existing Vegetation

Improve Soil Health

• Soils Testing
• Local Topsoil
• Imported Topsoil
• Roughen Soil Surface
• Stepped Slopes
• Contour Grading and Slope Rounding
• Decompact Soil
• Soil Nutrients
• Incorporate Materials

Improve Soil Health & Provide Cover

• Duff
• Mulch
• Compost

Short Term Cover

• Hydroseed Overview
  • Seed
  • Fiber
  • Straw
  • Tackifier
• Straw
• Hydroseed
• Bonded Fiber Matrix
• RECP (Jute Mesh)

Long Term Cover

• RECP (Netting)
• RECP (Blanket)
• RECP (Turf Reinforcing Mat)

Steep Slope Techniques

• Stepped Slope
• Cellular Confinement
• RECP Flap
• RECP Flap with Brush Layering
• RECP Wrap
• Soil Filled RSP
• Wire Blanket
• Wire Mesh Confinement

Planting

• Plant Selection
• TransPlant Application
• Noxious and Invasive Species
• Drill Seed
• Dry Seed
• Native Grass Sod
• Liner
• Seedling
• Brush Layering

Stormwater Treatment

• Biofiltration Strip
• Biofiltration Swale

Low Impact Development

• Overview
• Sidewalk Stormwater Planter
• Sidewalk Stormwater Tree Trench
• Parking Stormwater Planters
• Permeable Paving
• Additional Resources

Sediment Control

• Fiber Roll
• Compost Sock

References

• Webinars
• Guidance
• Research
• Presentations
• Magazine Articles
• Specifications by Others

Contour Grading and Slope Rounding

Images above illustrate slope rounding and contour grading proposed for Route 46 San Luis Obispo County between postmile 32.2 and 56.3

What is This Treatment?

Contour grading and slope rounding involves grading the project roadside with smooth, flowing contours that help integrate highway improvement within its surrounding environment. Concentrated water flows in graded valleys helps sustain vegetation in arid regions.

Besides helping make a highway facility compatible with its surroundings, this grading technique also helps reduce erosion and maintain water quality by breaking the slope into many smaller tributary areas dispersing runoff. Due to their higher moisture content, these focused drainage areas are better suited to supporting larger plants such as trees and shrubs than the planar slopes produced by rectilinear grading.

When to Use This Treatment?

• Consider using contour grading and slope rounding whenever permitted by the right of way limits.
• Typically used on cut slopes 2:1 and 3:1 (H:V) composed of rippable material. For specific maximum slope gradients, consult your geotechnical engineer.
• Comply with the guidance provided in the Highway Design Manual (HDM) Chapter 300, Topic 304.4 Contour Grading and Slope Rounding.
• Comply with the guidance for Slope Roughening/Terracing/Rounding/Stepping provided in Appendix A of the Caltrans Storm Water Quality Handbooks Project Planning and Design Guide.

Consider Using With:

• SSP 20-170 Local Topsoil
• SSP 20-040 Erosion Control (Hydroseed)
• SSP 20-055 Erosion Control (Compost Blanket)

Benefits:

• Reduced stormwater runoff volume and velocity.

• Improved infiltration rate.

• Improved soil water holding capacity within sculpted valleys.

• Improved potential for vigorous long term vegetation coverage.

• Topographic diversity supports a wider range of plant material.
• Reduces irrigation requirements by providing sheltered areas with higher moisture content that can be planted with higher moisture loving plant material such as trees and shrubs.
• Provides visual compatibility between highway facilities and their surrounding environment.

Limitations:

• May increase the cost of earthwork activities.

• Requires site accessibility by earthwork equipment.

Specifications

• Use standard department Earthwork specifications.

Plans and Details:

• No Standard Plans or Details available.

Estimate Information:

• No pricing information is currently available for contour grading.

Guidance:

• Highway Design Manual (HDM) Chapter 300, Topic 304.4
• Caltrans Contour Grading Slope Rounding Webinar

External Links:

• Schor, H. & Gray, D., 2007. “Landforming: An Environmental Approach to Hillside Development, Mine Reclamation and Watershed Restoration.” Published by John Wiley & Sons, Inc.