岬湾海滩灾后恢复过程与主控影响因子研究以澳洲Narrabeen海滩为例

位于澳洲悉尼附近的Narrabeen海滩经历着较频繁的风暴浪侵袭，在鲜有人工干预下，该海滩具有从风暴期间的沙坝剖面到常浪期稳定的滩肩剖面交替演变的自适应特征。为探明Narrabeen海滩在经历风暴浪后的自恢复动力，本文通过该海滩多年连续实测资料，分析典型风暴浪过后海滩剖面在常浪作用下的演变规律以及在恢复过程中的主要水动力要素。研究结果表明：Narrabeen海滩的恢复速率存在沿岸差异，沙滩中部恢复速率最快；在常年SE浪向主导下，小波高长周期波浪对北部以及中部剖面的恢复起促进作用，而潮动力对南部剖面在恢复期内的动态响应调控作用更强。本文据此提出考虑潮差的累积波能概念，发现其与南部海滩恢复能力间有良好的相关性。经调查，地形造成的浪向变化以及各剖面的地质地貌特征是造成该岬湾海滩恢复效率和恢复动力空间差异性的主要原因。此外，从年际时间尺度看，风暴剖面的恢复能力还受控于南方涛动因子。本文的研究方法和结论可为在极端海洋动力下岬湾海滩的防灾减灾和灾后修复提供有益借鉴。

Study on the recovery process and the main controlling factors for post-storm beach profiles of a headland bay: Taking the Narrabeen Beach in Australia as an example

Narrabeen Beach, located Sydney, Australia, has undergone frequent storm wave events. The beach form has an adaptive ability to evolve from storm profile to berm profile with little human intervention. In order to investigate the self-recovery capability of the headland bay after storm waves, this paper analyzes how beach evolves during the post-storm calm weathers and identify the main hydrodynamic factors that dominate the beach recovery based on the multi-year continuous measurement data of Narrabeen Beach. The results show that there are spatial differences along the shore in the recovery rates, with the fastest recovery rate in the middle of the beach. Besides, southeast breezes with small wave-height and long wave-period contribute most to the storm-profiles’ recovery, especially to the northern-to-central portion. Whilst for the southern part of the headland bay tidal force modulate the beach recovery efficiency more. Accordingly, a concept of cumulative wave energy considering tidal range is proposed by this study and found to well correlated with the self-recovery ability of the southern beach profile. Through investigation, variation of wave directions induced by topography, along with geological and geomorphological features all play a vital role on the spatial inhomogeneity of the recovery efficiency for the headland bay. In addition, from the secular time scale, the recovery ability of the storm profiles is also controlled by the Southern Oscillation Index. The analysis and findings of this paper can provide useful references for disaster prevention and mitigation, and post-disaster protection and restoration for a headland bay under extreme sea forces.