Zhang, C.; Zhang, Q.; Lei, G.; Cai, F.; Zheng, J., and Chen, K., 2018. Wave nonlinearity correction for parametric nearshore wave modelling. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 996–1000. Coconut Creek (Florida), ISSN 0749-0208.Many phase-averaged parametric nearshore wave models are based on the energy balance concept and use linear wave theory to calculate wave parameters (e.g., wave energy, wave height, wave setup). For a wave propagating into shallow water, however, its shape becomes skewed/asymmetric and the linear wave theory may not be appropriate. Seven cases of model-data comparison for regular wave transformation over sloping and barred beaches are carried out. It is shown that the model using linear wave theory underestimates the regular wave height near the breakpoint, and overestimates the breaking roller length in the surf zone. An empirical method is proposed to improve the performance of the parametric wave models in shallow waters by correcting the key model parameters to include wave nonlinearity effects. This includes (1) development of a new empirical formula for the nonlinear wave shape factor, (2) using a nonlinear wave celerity formula, and (3) implementing a new empirical formula for breaking roller slope. These formulas are functions of wave steepness and Ursell number. The proposed method systematically improves predictions of wave height, wave setup and roller evolution under regular wave transformation with different beach configurations. In particular, the peaks of wave height and mean water level near the breakpoint as well as the roller length variation in the surf zone are accurately captured by the wave nonlinearity-corrected model.
The general characteristics of coastal erosion in China are described in terms of the regional geography, the form of erosion, the causes of erosion, and the challenges we are facing. The paper highlights the relationship between coastal erosion and sea level rises, storm waves and tides, and the influence of global climate changes on coastal erosion along the coastal zone of China. The response of the risk of coastal erosion in China to climate changes has obvious regional diversity. Research into and the forecasting of the effects of climate changes on coastal erosion are systemic work involving the natural environment, social economy, and alongshore engineering projects in the global system. Facing global warming and continual enhancement of coastal erosion, suggestions for basic theoretical study, prevention technology, management system assurance, and strengthening the legal system are presented here.
The beach profile shape is an important research content of nearshore processes and coast engineering. For studying on the form and shape of beach equilibrium profile and the sand movement under the wave on the profile,this article processes the two dimension beach shape experiment using normal integer model with the natural sand on the wave and the sediment movement similar rule. The experiment proves that the artificial beach profiles prone to balance after wave work on them for certain time and fountain of sand to and fro the beach is also stable. The test shows the scour of the mixed wave is heavier than the simplicity oblique incident wave,and the simplicity oblique incident wave is heavier than the simplicity forward wave. For this,we must considerate the effect of different directions of incident wave on the profile when we construct the artificial beach. In contrast to the whole artificial beach profile transformation of all series,the whole of the beach profile was scoured. From the bank to the sea,there is a accumulation body of sand on the beach berm platform,and the heaviest erode is from the beach berm platform edge to the middle of the slope and the erode in the lower part of the slope is lighter and lighter to the sea.
Studies on the distribution and germination of Alexandrium sp. (A. tamarense + A. catenella) cysts in coastal areas of Southeast China showed that the cysts were only found at X1 and X2 of Xiamen Harbor, whose density was quite low (0.4 ind.g-1). In Guangxi, the cysts were found at G2 station, with a density of 2.5 ind.g-1. There were cysts at three stations at Minjiang River estuary. The density reaches maximum value at 4-6 cm sediment of M4 station, up to 6 ind.g-1. In Changjiang River estuary, the cysts distributed widely and had the largest density, up to 23.2 ind.g-1 at 8-10 cm sediment of DG-26 station. The distribution of Alexandrium sp.cysts was relevant to sediment type, sedimentation rate and current. Light had no effect on germination. With increasing temperature, germination and survival rates also increased, while the germination time decreased. Anoxia (0.01 mg O2.L-1) inhibited germination completely. Alexandrium sp. cysts could germinate throughout the year under favorable conditions.
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