Attachment C - Geotechnical investigation

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 Landstide a ‘ict te rh
Indicative Notional Recurrence Interval ee scriptor vel
Value Boundary
107 5x107 10 years The event is expected to occur over the design life. ALMOST CERTAIN A
2 20 years The event will probably occur under adverse conditions over the ~
10 ‘ 100 years design hie 7 LIKELY B
3 * :
107 azig 1000 years soo yeas The event could occur under adverse conditions over the design life. | POSSIBLE Cc
5x10° ares The event might occur under very adverse circumstances over the
107 10,000 years design life may UNLIKELY D
= . E
10° 5x10 PUG years The event is conceivable but only under exceptional circumstances
) 1 QO, 000 yeas over the design life RARE E
10° ae 1,000,000 years | 700-000 vears [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
5 Structure(s) completely destroyed and/or large scale damage requiring major engineering works for
200° S iS iS iS
200% 00% stabilisation. Could cause at least one adjacent property major consequence damage. Gos ernls :
60% 100% Extensive damage to most of structure, and/or extending beyond site boundaries requiring significant MAJOR 5
40° stabilisation works. Could cause at least one adjacent property medium consequence damage. ~
20% 2 Moderate damage to some of structure, and/or significant part of site requiring large stabilisation works. MEDIUM 3
ease 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
F Little damage. (Note for high probability event (Almost Certain), this category may be subdivided at a
0, = 4 J
irs notional boundary of 0.1%. See Risk Matrix ) ASEAN ‘

 

 

 

 

 

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.

G3) The Approximate Cost is to be an estimate of the direct cost of the damage. such as the cost of restatement 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 mclude 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

Australian Geomechanics Vol 42 No 1 March 2007
Form No. 68039 RL2 August 2010