Appendix B - Geotechnical Investigation Report

                                                   TABLE A1: LANDSLIDE RISK ASSESSMENT
                                      QUALITATIVE TERMINOLOGY FOR USE IN ASSESSING RISK TO PROPERTY
QUALITATIVE MEASURES OF LIKELIHOOD
   Approximate Annual Probability
   Indicative         Notional          Implied Indicative Landslide Recurrence Interval                                Description                                      Descriptor            Level
     Value            Boundary
      10-1                                     10 years                                   The event is expected to occur over the design life.                      ALMOST CERTAIN              A
                     510-2                                       20 years
                                                                                          The event will probably occur under adverse conditions over the
      10 -2                                   100 years                                                                                                             LIKELY                      B
                                                                                          design life.
                     510 -3                                      200 years
                                                                                          The event could occur under adverse conditions over the design
      10-3                                   1000 years                                                                                                             POSSIBLE                    C
                     510 -4                                                              life.
                                                                  2000 years
                                                                                          The event might occur under very adverse circumstances over the
      10-4                                  10,000 years                                                                                                            UNLIKELY                    D
                          -5                                                              design life.
                     510                                         20,000 years
         -5                                                                               The event is conceivable but only under exceptional circumstances
      10                                   100,000 years                                                                                                            RARE                        E
                          -2
                                                                                          over the design life.
                     510                                         200,000 years
      10-6                                1,000,000 years                                 The event is inconceivable or fanciful over the design life.              BARELY CREDIBLE              F
Note: (1)     The table should be used from left to right; use Approximate Annual Probability or Description to assign Descriptor, not vice versa.

QUALITATIVE MEASURES OF CONSEQUENCES TO PROPERTY
   Approximate cost of Damage
    Indicative       Notional                                                                Description                                                                 Descriptor            Level
      Value         Boundary
                                  Structure(s) completely destroyed and/or large scale damage requiring major engineering works for stabilisation. Could
       200%                                                                                                                                                       CATASTROPHIC                  1
                      100%        cause at least one adjacent property major consequence damage.
                                  Extensive damage to most of structure, and/or extending beyond site boundaries requiring significant stabilisation works.
       60%                                                                                                                                                        MAJOR                         2
                       40%        Could cause at least one adjacent property medium consequence damage.
                                  Moderate damage to some of structure, and/or significant part of site requiring large stabilisation works. Could cause at
       20%                                                                                                                                                        MEDIUM                        3
                       10%        least one adjacent property minor consequence damage.
        5%                        Limited damage to part of structure, and/or part of site requiring some reinstatement stabilisation works.                      MINOR                         4
                        1%        Little damage. (Note for high probability event (Almost Certain), this category may be subdivided at a notional boundary of
      0.5%                                                                                                                                                        INSIGNIFICANT                 5
                                  0.1%. See Risk Matrix.)
Notes: (2)      The Approximate Cost of Damage is expressed as a percentage of market value, being the cost of the improved value of the unaffected property which includes the land plus the
                unaffected structures.
          (3)   The Approximate Cost is to be an estimate of the direct cost of the damage, such as the cost of reinstatement of the damaged portion of the property (land plus structures), stabilisation
                works required to render the site to tolerable risk level for the landslide which has occurred and professional design fees, and consequential costs such as legal fees, temporary
                accommodation. It does not include additional stabilisation works to address other landslides which may affect the property.
          (4)   The table should be used from left to right; use Approximate Cost of Damage or Description to assign Descriptor, not vice versa.
Extract from PRACTICE NOTE GUIDELINES FOR LANDSLIDE RISK MANAGEMENT as presented in Australian Geomechanics, Vol 42, No 1, March 2007, which discusses the matter more fully.
February 2019