[Mapping and Assessing Terrain Stability Guidebook Table of Contents]



A TSFA report should normally include the following. The order and headings shown are to assist the author; they are not meant to establish a report template. Not all information is necessarily relevant in all cases.

Assignment information

Field assessment


Site information

Site descriptions for in-block harvesting, road locations and adjacent areas should be sufficiently complete, clear and concise to support the conclusions and recommendations. It is not sufficient to describe areas using terrain mapping and/or 5-class terrain stability mapping nomenclature or labels. Ensure descriptions of the following are provided:

Table 4. Example field indicators of potential slope instabilitya

Field indicators

Potential landslide type

  • recent landslide scars
  • revegetated landslide scars
  • high likelihood of landslides of the same type and size
  • partially revegetated strips (may also be snow avalanche tracks)
  • jack-strawed trees (trees tilted in various directions)
  • linear strips of even-aged timber
  • landslide debris piled on lower slopes
  • soil and rocks piled on the upslope side of trees
  • curved or sweeping trees (may also indicate snow creep)
  • mixed or buried soil profiles
  • poorly developed soils relative to other comparable slopes
  • tension fractures
  • poorly drained or gullied*, fine-textured materials <3 m deep on slopes >50%
  • poorly drained or gullied* coarse-textured materials on slopes >50%
  • wet site vegetation on slopes >50%
  • shallow, linear depressions
  • shallow, wet, organic soils on slopes >40%
  • debris avalanches
  • debris flows
  • debris slides
  • recently scoured gullies*
  • exposed soil on gully sides*
  • debris piles at the mouths of gullies*
  • vegetation in gully much younger than the adjacent forest
  • poorly developed soils on gully sides relative to adjacent slopes (repeated shallow failures continually remove the developed soil profile)
  • debris flows
  • debris slides
  • tension fractures
  • curved depressions
  • numerous springs at toe of slope, sag ponds
  • step-like benches or small scarps
  • bulges in road
  • displaced stream channels
  • jack-strawed trees (trees tilted in various directions), split trees
  • poorly drained medium- to fine-textured materials (e.g., till, lacustrine, marine and some glaciofluvial deposits) >3 m deep
  • mixed or buried soil profiles
  • ridged marine deposits
  • Slumps
  • slumps
  • talus or scattered boulders at base of slope
  • steeply dipping, bedrock discontinuities (bedding planes, joints or fracture surfaces, faults) that parallel the slope
  • bedrock joint or fracture surface intersections that dip steeply out of the slope

rock slides or rock fall (can be induced by excavation and blasting for roads)

*Apply the Gully Assessment Procedure Guidebook to any gullied areas on the Coast.
aModified from Land Management Handbook 18 (Chatwin et al, 1994). Consult LMH 18 for background information.

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