Slope Stability Report

6.3       Hazard Identification
A Hazard is defined as a condition with the potential for causing an undesirable consequence (the
landslide).
The hazard assessment given in this report is consistent with the procedures outlined in the report,
“A Method of Zoning Landslide Hazards” by MacGregor and Taylor, 2001. The following major site
features have been considered in determining a likelihood estimate or Frequency Analysis in turn, the
potential Hazard of the site in order of undertaking the final risk assessment for the proposed building
zone and immediate surrounds :

           ‐ The Natural Slope Angle                          ‐ The Natural Slope Shape/ Formation
           ‐ Local Area Geology                               ‐ Material Strength
           ‐ Concentration of Surface Water                   ‐ Evidence of Groundwater
           ‐ Evidence of Past Forms of Instability

From the results of studies undertaken by SMEC in similar terrain a correlation between relative
frequency and potential Hazard Rating has been determined as presented in the following table :‐




The following summarises the relative frequency calculation adopted following the guidelines of the
Landslide susceptibility analysis form extracted from the document ‘Landslide Susceptibility
Assessment Report’ for the City of Gold Coast, SMEC, August 2011. The complete form can be found
in appendix B;

               Feature                                  Description                        Risk Level
  Natural Surface Slope                               5 to 15 degrees                      Moderate
  Slope Shape                                       Planar/ Undulating                     Moderate
  Site Geology                                      Sedimentary Rock                       Moderate
  Soil Conditions                                    Residual > 3.0 m                         High
  Evidence of Groundwater                             None apparent                           Low
  Fill Height                                         Less than 1.0 m                      Moderate
  Cut Height                                      Between 1.0 to 3.0 m                     Moderate
  Slope of Cut Face                                    Less than 30°                          Low
  Material in Cutting                                        Soil                          Very High
  Cut Slope Support                               Timber Retaining Wall                       High
  Concentration of Surface Water                        Upper Slope                        Moderate
  Waste Water Disposal                                 Fully Sewered                       Moderate
  Stormwater Disposal                    All Stormwater Piped to Street Drainage              Low
  Evidence of Instability                          No Sign of Instability                     Low

As an opinion, the hazard for the nominated building location and surrounds of such is provisionally
outlined below:‐

               Applied Relative Frequency                                  Hazard Rating
                          0.68                                              Moderate