Detailed Terrain Stability Mapping

Terrain stability mapping is conducted to assess the likelihood of mass movement of soil (landslides). This is of particular importance to road construction. Harvesting of trees does not usually increase instability, but roads often do.

Detailed mapping, also known as Levels “B” or “C”, makes use of airphoto interpretation, but involves more field checks than Overview mapping. Categories of instability are:

I Nil

II Low

III Moderate

IV High

V Very High

Steep slopes and non-cohesive soils are most susceptible to mass movement, which is often triggered by water. Concentration of water drainage onto an unstable slope is a common cause of landslides.

Terrain stability mapping is used to minimize road construction on or above unstable terrain, and to trigger more detailed Terrain Stability Field Assessments and road designs for those areas that cannot be avoided.