Gosford Coastal Lagoons Flood Studies Comparison of Opening Procedure Avoca and Cockrone Lagoons

Storage Volumes:\r\nThe modelling showed that the approach developed for Terrigal and Wamberal Lagoons could be satisfactorily applied to Avoca Lagoon for the opening of 14 September 1993. In discussions with Paterson Consultants it became apparent that the storage volume of the Lagoon was critical for establishing the peak outflow from the Lagoon. A considerable effort was undertaken in this regard which revealed that a table of height/area of Avoca Lagoon was in error at a level of I.0 m. In addition it was determined that the Mike-II and RUBICON models determine different storage capacities of the lagoon. There was insufficient time to completely resolve this issue, however preliminary work suggested that the Mike- 11 model was over-calculating storage. The differences in storage make no significant difference to the peak flood level.\r\nComparison of Results:\r\nFor Wamberal, Avoca and Cockrone Lagoons the peak flood levels from both approaches should be very similar. This is because the berm height is the major control and the peak flood level is only just (0.3m) above the berm level. For Terrigal Lagoon the differences in the two approaches are likely to be more significant as the beach berm is much lower (2.5m AHD) and the peak flood level approximately 0.5m higher than the berm.\r\nAdditional Work:\r\nIt is recommended that data be collected for future openings. If the data are suitable they should be used in further verification of the hydraulic models.

储水量：
建模结果显示，针对特里加尔潟湖（Terrigal Lagoon）与万伯勒尔潟湖（Wamberal Lagoon）开发的分析方法，可较好地应用于1993年9月14日开闸工况下的阿沃卡潟湖（Avoca Lagoon）。在与帕特森咨询公司（Paterson Consultants）沟通后发现，潟湖储水量是确定其峰值出流量的关键参数。为此开展了大量调研工作，结果发现阿沃卡潟湖的水位-面积对照表存在1.0米水位处的计算误差。此外，经确认，Mike-II与RUBICON模型对该潟湖的储水容量计算结果存在显著差异。由于时间有限，未能完全解决这一问题，但初步研究表明Mike-II模型高估了潟湖储水量。不过储水量的差异对峰值洪水位并无显著影响。

结果对比：
针对万伯勒尔潟湖、阿沃卡潟湖与科克龙潟湖（Cockrone Lagoon），两种分析方法得到的峰值洪水位应极为接近。这是因为滩肩高度是洪水位的主要控制因素，且峰值洪水位仅比滩肩高程高出约0.3米。而针对特里加尔潟湖，两种方法的计算差异可能更为显著：其滩肩高程更低（2.5米澳大利亚高程基准（Australian Height Datum, AHD）），且峰值洪水位较滩肩高程高出约0.5米。

补充工作建议：
建议针对未来的潟湖开闸工况收集相关实测数据。若数据质量符合验证要求，可用于进一步验证该水力模型。