Landslide Hazard Report_compressed

Specialists in transport geotechnics

2 METHODOLOGY

2.1 General

This report presents a portion of the above requirements. The methodology adopted in the initial
stage 1 slope assessment is noted below:
   1. Desktop study
      a) Review of available relevant planning documentation including layout, topographic
          plans and flood data.
      b) A review of existing Hazard mapping (where available), aerial photographs and
          various published information to assist in identifying past activity.
      c) Collation of regional soil and geological data.
   2. Site investigation (non-intrusive)
   3. Landslide Risk Assessment (qualitative risk to property)

The methodology for conducting the Landslide Risk assessment is in general compliance with
Australian Geomechanics Society (AGS), Volume 42, No.1 March 2007. Key details are
discussed below. The AGS framework for Landslide Risk management is presented in Figure 3.0
below.

2.2 Landslide Risk Assessment
This qualitative risk assessment has been carried out to assess the geological hazards on the
site and attempt to define the likelihood of that hazard becoming an event, and as a consequence
the resultant risk to property. A qualitative assessment ranks risk on a scale as opposed to a
quantitative risk assessment that defines the risk as a numerical probability.
A risk is made up of the product of the likelihood of an event, and the consequences of that event
occurring. We have used a methodology guided by the paper ‘A National Landslide Risk
Management Framework for Australia’; Volume 42 March 2007 published by the Australian
Geomechanics Society in 2007 (AGS 2007). The risk matrix from AGS 2007 is attached in
Appendix B.
This document was created in an attempt to standardise the terms and methodologies used for
risk assessment for landslide events in Australia, and also to formalise the procedures in
conducting risk assessments. The guidelines use common terms and methods of assessment,
combined with a risk matrix to define risk. The terms used in this document that reference
definitions in AGS 2007 are written in bold.
For example, the likelihood of a small rock falling may be assessed as ‘likely’ (e.g., the
assessment that a rock will likely fall in the next significant rain event) whilst the consequences of
that particular rock impacting a building may be ‘insignificant’ (e.g. the rock is so small that the
building damage might be insignificant). The resultant risk relating to that particular hazard could
then be assessed using the AGS 2007 risk matrix from Appendix B to be ‘low’.
The risk assessments are based on CGC’s assumptions and judgements. The risks assessed
using these methods are generally ranges, and in some cases span two or more categories of
risk. The range of values indicates the uncertainty in the data used to estimate the likelihood and
consequences of events. Further investigation work may be required to reduce this uncertainty.




10 May 2022                        CGC-SR-2022-011-R01-Rev01                                  Page 3