Condition

Predicted state

Parameter range

A possible influence of factors not modeled

SI > 1.5

Stable slope zone

Range cannot model instability

Significant destabilizing factors are required for instability

1.5 > SI > 1.25

Moderately stable zone

Range cannot model instability

Moderate destabilizing factors are required for instability

1.25 > SI > 1.0

Quasi-stable slope zone

Range cannot model instability

Minor destabilizing factors could lead to instability

1.0 > SI > 0.5

Lower threshold slope zone

Pessimistic half of range required for instability

Destabilizing factors are not required for instability

0.5 > SI > 0.0

Upper threshold slope zone

Optimistic half of range required for stability

Stabilizing factors may be responsible for stability

0.0 > SI

Defended slope zone

Range cannot model stability

Stabilizing factors are required for stability