Referenced Document - OPW20-0037

Mr Andrew Jensen                                                                                        20013-001-Rev0
                                                                                                        4 February 2020

3.0     ASSESSMENT OF LAND STABILITY
3.1   Existing Conditions
An extract from the NC Natural Hazards Overlay is shown below (Ref. extract in Text Figure 10). The
mapping indicates that much of the allotment is classified as being a “Landslide Hazard Area”, although not
the northern and southern parts including the area where building works are proposed.




Text Figure 10: Extract from Noosa Council Plan Natural Hazards Overlay Mapping

It is noted that this designation has been assigned at a coarse resolution, and largely records that the ridge
at the south of the site is not classified as a “Landslide Hazard Area”. The mapping is a broad-scale
indication of the potential landslide susceptibility only and is superseded by site specific investigation and
analysis works.

At the time of our visit, the ground did not exhibit any significant recent or historic indicators of slope
instability. No landslide back scarps, groundwater springs, or tension cracks were observed.

3.2   Stability Assessment
The risk assessment for this project has been carried out following AGS 2007 Practice Note Guidelines for
Landslide Risk Management. Relative levels of risk and their implications are given in Table 1 below and the
Qualitative Terminology for Use in Assessing Risk to Property is also attached.
 Table 1: Stability Risk Levels

 Risk Level            Example Implications(1)
                       Unacceptable without treatment. Extensive detailed investigation and research, planning
       Very High
 VH                    and implementation of treatment options essential to reduce risk to Low; may be too
       Risk
                       expensive and not practical. Work likely to cost more than value of property.
                       Unacceptable without treatment. Detailed investigation, planning and implementation of
 H     High Risk       treatment options required to reduce risk to Low. Work would cost a substantial sum in
                       relation to the value of the property.
                       May be tolerated in certain circumstances (subject to regulators’ approval) but requires
       Moderate
 M                     investigation, planning and implementation of treatment options to reduce risk to Low.
       Risk
                       Treatment options to reduce to Low risk should be implemented as soon as practicable.
                       Usually acceptable to regulators. Where treatment has been required to reduce the risk
 L     Low Risk
                       to this level, ongoing maintenance required.
       Very Low
 VL                    Acceptable. Manage by normal slope maintenance procedures.
       Risk
 Note: (1) The implications for a particular situation are to be determined by all parties to the risk assessment and may
 depend on the nature of the property at risk; these are only given as a general guide.




                                                            7/11