Erosion Control Structures

Erosion control structures are used to manage surface runoff and soil loss. Water and sediment control basins, diversion terraces, and grassed waterways are the most common upland erosion control measures that can be implemented, depending on the size of the watershed and type of erosion (i.e., sheet, rill or gully erosion).

Every site is unique. Erosion control structures should be planned and built by qualified professionals who understand local soil and drainage conditions.

Who to contact:

  • Conservation Authority staff
  • Certified erosion control contractors

Types of Erosion Control Structures

Diversion Terraces

Diversion terraces are low, grass-covered ridges built across slopes to slow down and redirect surface water. They help control sheet erosion by channeling runoff into a tile drain or grassed outlet.

Key Benefits

  • Reduces slope and length and water velocity
  • Protects topsoil and reduces sediment loss
  • Works well in combination with cover crops and contour farming

Maintenance

  • Inspect after large storms and repair any erosion or washouts
  • Maintain a dense grass cover by mowing and reseeding as needed

Grassed Waterways

For larger drainage areas (over 35 acres/14 ha), grassed waterways provide a stable, vegetated channel that safely carries runoff to an outlet.

Features

  • Follows natural drainage paths
  • Designed to handle runoff from a 10 year storm
  • Side slopes of 10:1 allow easy passage for farm machinery
  • Tile drainage should be offset from the centre to avoid damage

Maintenance

  • Inspect annually and after major storm events
  • Keep grass thick and healthy through regular mowing and fertilization
  • Reseed bare areas promptly to prevent erosion

Do

  • Raise implements when crossing
  • Harvest forage crops from waterway
  • Bring crop rows in at an angle when possible

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  • Spray herbicides on the grassed area
  • Use the waterway as a travel lane or turn strip
  • Plant headlands along the waterway

Water and Sediment Control Basin (WASCoB)

A WASCoB is an earthen berm built across a natural drainage way. It temporarily holds back runoff, allowing water to soak into the soil or flow out slowly through a tile drain system (within 24 hours).

When To Use

  • Ideal for areas with rill erosion and watersheds up to 25 acres (10 ha)
  • Larger watersheds may require a series of basins

Design Options

  • Broad-based berm: 10:1 slope; can be cropped
  • Narrow-based berm: 2:1 slope; permanently vegetated

Maintenance

  • Check berms, inlets, and tiles for cracks, settlement, or burrowing animals
  • Mow occasionally to control woody growth
  • Use cover crops or conservation tillage to reduce sediment buildup
  • Remove excess sediment from the ponding area
  • Inspect and repair the spillway after major storms

  • Use subsoil with a least 10% clay
  • Avoid stones or debris
  • Compact soil properly
  • Install tile drainage before earthwork begins

Best Practices for Long-Term Success

Erosion control structures perform best when combined with upland management practices that minimize soil loss, such as

  • Crop rotation
  • Conservation tillage
  • Perennial cover
  • Use of cover crops

Integrating these practices extends the life and effectiveness of erosion control systems.

Resources