Summarizing of river mouth processing method based on comparative study on river mouth in Japan

针对高浪造成的河口堵塞，已有多种治理措施，如整治码头、闸门、涵洞、人工疏浚等。根据对日本不同河口的大量实地观测，总结了每种方法的相对优缺点。其中，人工疏浚方法对邻近海岸和河口环境的影响较小。但是，河口吐出的沙子会中断流入大海的污水。适当冲洗沙坑可减轻邻近地区的水浸强度。初始喷沙高程通过泄洪、潮位和泥沙输移过程的复杂相互作用影响冲刷的启动和发展。为了研究这一复杂的过程，发展了一种数值计算方法。经验证后，用来研究在潮汐和高洪水共同作用下，初始喷沙水位对河段时间变化和相应的河床地形发育的影响。此外，结合流域内的泥沙平衡和海滩过程，研究了河口附近的沉积过程。

There have been several countermeasures against river mouth blockage due to high waves, such as training jetties, gate, culvert and artificial dredging. The relative advantages and disadvantages of each method are summarized based on a numerous field observations at various river mouths in Japan. Among these, it is noted that an artificial dredging method has quite less influence to adjacent coastal and estuarine environments. But, the presence of sand spit at a river mouth interrupts effluent flood flow into the sea. An appropriate flushing of the sand spit can reduce flooding intensity in the adjoining areas. Initial sand spit elevation influences initiation and development of flushing through a complex interaction of effluent flood discharge, tidal level and sediment transport processes. To investigate this complicated process, a numerical computation method is developed. After verification, it is used to investigate the influence of initial sand spit level on the time-variation of river stage and corresponding development of bed topography under the actions of both tide and high flood flow. Furthermore, sedimentation process around a river mouth is studied in connection with sand budget in a river basin and beach processes.