[Mapping and Assessing Terrain Stability Guidebook Table of Contents]

Appendix 3. Example classification: Soil erosion potential

Class

Rating

Example criteria

Management implications

VL

Very low

  • Blocky colluvial deposits
  • Terrain dominated by competent bedrock

No or only very minor surface erosion.

L

Low

  • Morainal veneers; most rubbly colluvial deposits with high coarse fragment content

Expect minor erosion of fines in ditch lines and disturbed soils.

M

Moderate

  • Morainal blankets (depends on texture and coarse fragment content; varies across the province)
  • Glaciofluvial gravels
  • Soft, friable bedrock

Expect moderate erosion when water is channeled down road surfaces or ditches.

H

High

  • Some morainal blankets steeper than 60%, or steeper than 30% if gullied or poorly drained (depends on texture and coarse fragment content; varies across the province)
  • Fine textured lacustrine (silts & clays), glaciolacustrine, glaciomarine, glaciofluvial or aeolian silts, slopes less than 15%
  • Glaciofluvial or fluvial sands with low bulk density, slopes less than 30%
  • Colluvial deposits derived from the above materials with the same slope or moisture criteria
  • Colluvium derived from soft, friable rock (e.g., soft phyllites, some pyroclastics), steeper than 60% or steeper than 30% if gullied

Significant erosion problems can be created when water is channeled onto or over exposed soil on these sites.

VH

Very high

  • Fine textured lacustrine (silts & clays), glaciolacustrine, glaciomarine, glaciofluvial or aeolian silts, slopes steeper than 15%, or gullied or poorly drained.
  • Glaciofluvial or fluvial sands with low bulk density, steeper than 30% or gullied or poorly drained
  • Peat, organic soils or tufa on sloping ground
  • Colluvial deposits derived from the above materials with the same slope or moisture criteria

Severe surface and gully erosion problems can be created when water is channeled onto or over these sites.

aThis is an example classification only. Modifications will be necessary to suit local conditions.


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