Analysis of multi-scale morphodynamic behavior of a high energy beach facing the Sea of Japan
Analysis of multi-scale morphodynamic behavior of a high energy beach facing the Sea of Japan
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DOI：
10.3389/fmars.2015.00051
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发表时间：
2015
影响因子：
3.7
通讯作者：
H. Karunarathna;H. Mase;Y. Baba
中科院分区：
文献类型：
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作者：
H. Karunarathna;H. Mase;Y. Baba
为了研究海滩的多尺度地貌动力学行为，对位于日本新泻县柔津-绪方海岸的绪方波浪观测码头所测得的月度跨岸海滩剖面进行了分析。面对日本海的绪方海滩，受到高能海浪的影响，具有强烈的冬/夏季节性特征。测得的海滩剖面具有很大的变异性，测量地点的岸线位置跨岸移动超过20m，海滩下沉超过4m。海岸线位置似乎遵循入射海浪气候的季节变化，月平均入射有效波高与实测海岸线位置之间的相关系数为0.77。夏季，海滩的变化主要集中在剖面的潮下部分，而在冬季，上层海滩的变化很大。海滩剖面形状在时间上在三种不同的海滩状态之间旋转；(I)凹面反射剖面；(Ii)具有潮下护堤的剖面；(Iii)平缓的耗散剖面。对剖面的经验正交函数(EOF)分析表明，海滩剖面形状的变化主要受(A)上滨面陡化、(B)潮下护堤的发展和消散以及(C)总剖面坡度的变化所主导，这些变化具有比季节循环特征更长的特征。将EOFs与南方涛动指数、太平洋年代际涛动指数等气候指数进行比较，发现该地区的气候变率与廓线变化之间存在着明显的相关性。分析还表明，珠江-绪方海岸的形态变化与其他地方发现的类似海滩有相似之处，但也有一些明显的时空差异。
Monthly cross shore beach profiles measured at the Ogata Wave Observation pier located in Joetsu-Ogata Coast, Niigata Prefecture, Japan, was analysed to investigate multi-scale morphodynamic beach behaviour. The Ogata beach, facing the Sea of Japan, is subjected to high energy wave conditions with that has a strong winter/summer seasonal signature. The measured beach profiles at the beach show very significant variability where cross-shore movement of shoreline position and lowering of the beach at the location of measurements exceed 20 m and 4 m respectively. The shoreline position seems to follow the seasonal variability of incident wave climate where a correlation coefficient of 0.77 was found between monthly averaged incident significant wave height and the measured monthly shoreline position. During the summer months, the beach variability mostly concentrated to in the sub-tidal part of the profile, while a significant amount of upper beach change was observed during the winter months. The beach profile shape was found to rotate between three different beach states in time; (i) concave reflective profile; (ii) profile with sub-tidal berm; and (iii) gentle, dissipative profile. Empirical Orthogonal Function (EOF) analysis of the profiles show that the variability of beach profile shape is dominated by (a) upper shoreface steepening; (b) sub tidal berm development and dissipation; and (c) variability of the overall profile slope, which have some longer than seasonal cyclic signatures. Comparison of temporal EOFs with climate indices such as Southern Oscillation Index and Pacific Decadal Oscillation index shows notable some correlations between profile change and climatic variability in the region. The analysis also shows that the morphological variability of Joetsu-Ogata Coast has similarities and some distinct spatial and temporal differences to beaches of similar kind found elsewhere.