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Erosion - PowerPoint PPT Presentation


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Erosion. What is it?. Movement of soil materials by the action of water, wind or gravity. Background. Erosion is a problem when it results from, or is accelerated by our activities Vegetation and an “intact” forest floor limit erosion potential

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Presentation Transcript
what is it
What is it?
  • Movement of soil materials by the action of water, wind or gravity
background
Background
  • Erosion is a problem when it results from, or is accelerated by our activities
  • Vegetation and an “intact” forest floor limit erosion potential
  • Harvesting can lead to erosion problems by removing the canopy and destroying lesser vegetation
impacts of erosion
Impacts of Erosion
  • Possible deposition of soil in waterways, damaging fisheries and aquatic ecosystems
  • Damage to roads, reforested areas and forest stands
  • Gravitational erosion (landslides) may cause extreme damage to the environment, property, and threat to human life
impacts of erosion1
Impacts of Erosion
  • Erosion may reduce site productivity by
    • Displacing forest humus and topsoil layers
    • Removing or destroying soil structure of fine-textured mineral soils
    • Preventing plant establishment
    • Covering top soil layers with subsoil
sensitive sites for erosion
Sensitive Sites for Erosion
  • Steep slopes
  • Wind-deposited soils (dune areas)
  • Deep alluvial deposits, especially adjacent to major river systems
  • Water crossings and all riparian areas
  • Road construction areas (unstable cuts, fills ,ditching)
bmp s for erosion
BMP’s for Erosion
  • Steep Slope Areas
    • Risk of erosion increases with slope
    • Even minor rutting may cause erosion problems on slopes
    • Risk of damage and environmental significance is highest on fine textured soils
bmp s for erosion1
BMP’s for Erosion
  • Steep Slope Areas
    • Preplan skidding on steep rolling terrain
    • Avoid skidding up and down steep slopes (> 30%) where possible
bmp s for erosion2
BMP’s for Erosion
  • Steep Slope Areas
    • Winch wood off short slopes, or reach and remove it with a buncher
    • Dispersed skidding may be preferred to limit the creation of ruts on slopes
    • Cross-slope skidding may be preferred on moderate slopes with steps (within safety limits)
bmp s for erosion3
BMP’s for Erosion
  • Steep Slope Areas
    • Avoid skidding through narrow valley drainage ways
    • Avoid even minor rutting on slopes
    • Discontinue skidding sooner (e.g., due to wet weather conditions) on hilly terrain
bmp s for erosion4
BMP’s for Erosion
  • Steep Slope Areas
    • Some timber on steep slopes should be bypassed because of safety, operational and site damage concerns
bmp s for erosion5
BMP’s for Erosion
  • Road Construction
    • Maintain stable slopes on ditch line, road fills and cuts
    • Maintain 1:1 sloping of exposed material
    • Reinforce slopes (re-vegetate or use logging debris)
    • Crown and grade road surfaces
bmp s for erosion6
BMP’s for Erosion
  • Road Construction
    • Use energy dissipaters such as boulders, slash, etc. to interrupt water flow in ditches
bmp s for erosion7
BMP’s for Erosion
  • Road Construction
    • Plan to keep runoff water and sediment away from riparian areas
    • Use diversions such as tap ditches to direct run off water into areas of undisturbed vegetation or settling ponds
bmp s for erosion8
BMP’s for Erosion
  • Aeolian Soils
    • Roads and landings built on “blow sand” (aeolian sands) are subject to wind erosion
    • Limit the size of landings and all areas of exposed soil
bmp s for erosion9
BMP’s for Erosion
  • Aeolian Soils
    • Cover retired landings, road cuts, borrow pits (road ways) with duff, logging debris or chipper debris
    • Replant these areas quickly (Pj or Pr)
    • Avoid heavy site preparation that may promote wind erosion and impede reforestation
bmp s for erosion10
BMP’s for Erosion
  • Deep alluvial soils
    • Limit the extent of clearcut harvesting (size of blocks, total % of area) on these sites adjacent to large rivers
    • Plan smaller cuts with prolonged return periods
bmp s for erosion11
BMP’s for Erosion
  • Riparian Areas
    • Erosion in riparian areas is a significant environmental problem
    • Adhere to guidelines for riparian areas
    • Re-vegetate or reinforce exposed soils in crossing areas
best management practices
Best Management Practices
  • Riparian Areas
    • Manage ditch line runoff to minimize sedimentation
    • Maintain 100 meter “no grubbing zone” (as per guidelines)
    • Plan water crossings to take advantage of low slope areas, rocky shores, etc.