2019-07-09 P&E Agenda - Item 10 - Attachment 1 - Coastal Hazards Risk, Vulnerability and Adaptation Assessment

Noosa Shire Council Coastal Hazard Mapping                                                                 6
Storm Tide Hazard Assessment




         Future climate 2100 scenarios were also reported by Aurecon (2013). These assessments simply
         added a 0.8 m SLR allowance to the current climate design water levels. This approach has been
         followed, using the SLR allowances summarised in Table 2-1, to estimate the 2040 and 2070 open
         coast 100 year ARI water levels. Current climate and future climate open coast design water levels
         adopted for the Noosa CHAP storm tide hazard mapping are provided in Table 2-2.

                        Table 2-2     100 year ARI Open Coast Storm Tide Levels (mAHD)

           Location                      Current             2040             2070               2100
           Peregian Beach                  2.97              3.17             3.47               3.77
           Marcus Beach                    3.01              3.21             3.51               3.81
           Sunshine Beach                  3.17              3.37             3.67               3.97
           Noosa Head                      3.17              3.37             3.67               3.97
           Noosa Main Beach                2.62              2.82             3.12               3.42
           Noosa River Entrance*           1.63              1.83             2.13               2.43
           Noosa North Shore               2.73              2.93             3.23               3.53
           Teewah Beach                    3.18              3.38             3.68               3.98

         *wave setup not included within river entrance

         The current and 2100 climate design water levels reported by Aurecon (2013) and reproduced in
         Table 2-2 included an allowance for wave setup; however, it is noted that Aurecon (2013) did not
         provide details of how wave setup was derived other than to reference the NDRP Storm Tide
         Hazard Interpolation Study (GHD 2014). The NDRP study adopted wave setup estimates reported
         by Hardy et al. (2004), noting that this study only considered surge and wave conditions generated
         by tropical cyclone events. For the Sunshine Coast region, design water level and wave statistics
         are likely to be dominated by non-cyclonic weather systems up to at least the 100 year ARI.
         Consequently, there is some concern that the wave setup allowances reported by Aurecon (2013)
         are not representative of actual wave conditions that occur along the Sunshine Coast, particularly
         for return periods up to and including the 100 year ARI. For storm erosion hazard assessment
         discussed in Section 3.5, the wave setup contribution to the design water level at the shoreline has
         been estimated following an alternative approach.

2.2.1    Open Coast Storm Tide Assessment
         Open coast storm tide hazard mapping has been produced using a ‘bathtub’ mapping approach.
         The mapping methodology involved extrapolating the point location output summarised in Table
         2-2 across the adjacent coastal land. The open coast shoreline throughout the Noosa region is
         characterised by either an established dune system or rocky headland. These natural features
         provide the adjacent land areas a degree of protection from open coast storm tide inundation and
         therefore this hazard area is confined to a relatively narrow strip along open coast beaches. The
         influence of storm tide conditions on catchment flooding (i.e. land adjacent to the lower Noosa
         River) has been mapped separately and is described in Section 2.2.2.

         It is noted that the water levels in Table 2-2 are considered representative of the ‘sustained peak’
         level during a storm tide event. These levels do not account for wave runup, the intermittent


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