Wave-Swash Interactions and Saturation in the Swash Zone.

This study draws on 4 existing and 5 new sets of swash zone data acquired on swell dominated, sandy beaches of the east Australian coastline, and constitutes one of the most comprehensive sets of swash zone data currently available. Previous studies of swash have loosely identified a lower and upper swash zone characterised by different hydrodynamic processes. By integrating data acquired simultaneously in Eulerian and Lagrangian reference frames a new method has been developed that identifies this critical process boundary on the basis of uniform hydrokinematics. For the wide range of beaches investigated in this study the lower or "transition zone" is 0.53 ± 0.21 of the swash zone length. Wave-swash interactions are therefore ubiquitous and spatially extensive. This study indicates that vertical swash excursion lengths conform to a Normal distribution on most beaches.The presence of wave-swash interaction within the lower swash zone provides a plausible explanation for the transformation from Rayleigh distributed wave heights within the surf zone to Normally distributed vertical swash excursions. This study highlights the need for further investigation of the causes and physical meaning of rolloff in shoreline spectra.本研究依托澳大利亚东海岸受涌浪主导的砂质海滩上采集的4套现有冲流带（swash zone）数据与5套新增数据集，是当前可获取的最全面的冲流带数据集之一。过往关于冲流带的研究曾粗略划分出上下两个冲流带区段，二者以迥异的水动力过程为特征。本研究通过整合欧拉参考系（Eulerian reference frame）与拉格朗日参考系（Lagrangian reference frame）同步采集的数据，提出了一种基于统一水动力学特性识别该关键过程分界的全新方法。针对本研究调研的各类海滩，下段（或称“过渡带”）的长度约为冲流带总长度的0.53±0.21。由此可见，波浪-冲流相互作用普遍存在且空间分布范围极广。本研究表明，多数海滩的垂向冲流位移长度符合正态分布（Normal distribution）。冲流带下段存在的波浪-冲流相互作用，可合理解释碎波带（surf zone）内瑞利分布（Rayleigh distribution）波高向垂向冲流位移正态分布的转变过程。本研究强调，需进一步开展岸线频谱（shoreline spectra）滚降现象的成因与物理内涵相关研究。