ECM_22343537_v1_Coastal Hazard Assessment · 132000.200173.1

                                                               Internal use only




              6.1.2         Short-term Erosion (C)
              The Department of Environment and Heritage Protection (2013) recommends the calculation of short-term
              erosion based on a 100-year ARI storm event using the method developed by Vellinga (1983). Figure 18
              shows a conceptual representation of the erosion and accretion zones associated with storm induced
              erosion predicted by Vellinga (1983). The Department provides the following recommendation in relation
              to defining a storm event:

                        “For a tide-dominated coast where storm tide levels can be large, the parameters
                        adopted for the minimum design storm are:
                                storm tide level corresponding to an average recurrence interval of 1-in-
                                 100 years; and,
                                wave height for a moderate storm using the 1-in-20-year significant wave
                                 height (Hs).

                        However, for wave-dominated coastlines where extreme storm tide levels can be
                        relatively minor, such as the Gold Coast, the significant wave height and duration
                        of the storm event are major factors influencing short term erosion, rather than
                        storm tide. Hence it may be necessary to consider a larger wave event (for
                        example, a storm event with a 1-in-100 ARI) and a moderate storm tide level.
                        Decisions on appropriate parameters to be used must be based on local
                        conditions and the experience of the coastal engineer undertaking the
                        assessment.”




              Figure 18 Sketch of pre-storm and predicted post-storm profiles based on Vellinga (1983)


              In relation to the probability of such an event occurring the Department of Environment and Heritage
              protection (2013) states:

                       “Although the abovementioned probability of occurrence may appear to be fairly
                       high, it is considered that this choice is reasonable when considered in
                       conjunction with the method used to determine erosion prone area widths. This


              13 February 2023         2 ARAKOON CRESCENT, SUNSHINE BEACH                                PA3303   26


Document Set ID: 22343537
Version: 1, Version Date: 16/03/2023