Attachment 3 - Geotechnical Report

PRACTICE NOTE GUIDELINES FOR LANDSLIDE RISK MANAGEMENT 2007
APPENDIX C: LANDSLIDE RISK ASSESSMENT
QUALITATIVE TERMINOLOGY FOR USE IN ASSESSING RISK TO PROPERTY

QUALITATIVE MEASURES OF LIKELIHOOD

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Approximate Annual Probability Implied Indicative Landslide peseription peseriptor Level
Indicative Notional Recurrence Interval P P
Value Boundary
10! 5x102 10 years 0 The event is expected to occur over the design life. ALMOST CERTAIN A
years 7 a 7 7 ~onditions Ov!
102 100 years event will probably occur under adverse conditions over the LIKELY B
ech 5x107 200 years gn - — - - =
10° 7 1000 years 2000 vears The event could occur under adverse conditions over the design life. | POSSIBLE Cc
10" 5x10 10,000 years : The event might occur under very adverse circumstances over the UNLIKELY D
10° Sxl0° 20,000 years Teagan conceivable but only under exceptional circumstances
100,000 years he event is conceivable but only under exceptional circumstances | p app E
5x10 200,000 years over the design life.
10° 1,000,000 years . The event is inconceivable or fanciful over the design life. BARELY CREDIBLE

 

 

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
200% Structure(s) completely destroyed and/or large scale damage requiring major engineering works for CATASTROPHIC 1
stabilisation. Could cause at least one adjacent property major consequence damage.
100% E = ; : er
0, xtensive damage to most of structure, and/or extending beyond site boundaries requiring significant
60% “eat, : : MAJOR 2
40% stabilisation works. Could cause at least one adjacent property medium consequence damage.
20% Moderate damage to some of structure, and/or significant part of site requiring large stabilisation works. MEDIUM 3
° 10% Could cause at least one adjacent property minor consequence damage.
5% 1% ° Limited damage to part of structure, and/or part of site requiring some reinstatement stabilisation works. MINOR 4
05% Little damage. (Note for high probability event (Almost Certain), this category may be subdivided at a INSIGNIFICANT 5
notional boundary of 0.1%, See Risk Matrix.)
Notes: (2) The Approximate Cost of Damage is expressed as a percentage of market value, being the cost cf 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

91 Australian Geomechanics Vol 42 No 1 March 2007