Geotehnical Investigation Report · OPW22/0140

                               PROPOSED UNIT DEVELOPMENT
                               37 BOTTLEBRUSH AVENUE, NOOSA HEADS

5.0       SLOPE STABILITY ASSESSMENT
5.1       Existing Conditions
The Noosa Planning Scheme 2020 includes a landslide hazard overlay map (Ref. extract in Text Figure 8).
Mapping indicates that most of the site is within a Moderate (pale yellow shading) Landslide Hazard Area.




                                                      Lot boundary




Text Figure 8: Extract from NSC landslide hazard overlay mapping

It should be noted that the Noosa landslide hazard map is a broad-scale indication of the potential
landslide susceptibility and is superseded by this site-specific assessment. Our observations of surface
features relevant to this slope stability assessment are summarised as follows:

        The existing building was noted to be in reasonable structural condition based on an external
         assessment and showed no signs of instability (e.g. no significant cracks in rigid walls etc.).
        No indicators of recent global slope instability were observed, i.e. no landslide scarps or ‘hummocky’
         ground was evident across the proposed building area.
        No signs of groundwater seepage ‘springs’ were observed across the proposed development area.
        Overall inferred natural ground slopes were relatively moderate.

5.2        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 2 and the
Qualitative Terminology for Use in Assessing Risk to Property is also attached in Appendix B.
Table 2: 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 to
 L       Low Risk
                       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.




13 May 2022
Report No. 22151-001-Rev0                                   7