Methodology of Beach Erosion Control for the Reduction of a River Delta and Its Application

在本研究项目中，基于沉积系统中沙质海岸的稳定及其大尺度海岸行为，研究了一种用于减少河流三角洲的海滩侵蚀控制方法。研究了黑部河、阿部河、富士河、天龙河等河流三角洲海岸的侵蚀过程，发现明显存在两种侵蚀波类型导致的岸线变化模式。将第一种模式定义为沿海岸向下传播的侵蚀波作为扩散现象；将第二种模式定义为沿海岸向下传播的侵蚀波作为波浪现象。结果表明，侵蚀作用导致的岸线变化可以描述为时空变化，以扩散现象的形式沿海岸向下传播，在这种扩散现象的基础上，岸线变化以波浪现象的形式传播，速度快于岸线变化。由于河口泥沙输入的初始条件和边界条件以及河流三角洲的局部变化，第一种模式的侵蚀波会发生正、负两种形式的变化。引入具有代表性的风暴潮和涌浪，建立了岸线变化的长期预测模型。并将其应用于六幡海岸长期岸线变化的后验。在利用海岬和大尺度海岸行为控制滩涂侵蚀方法的基础上，研究了建立滩涂稳定滩涂的方法。它的应用是在新泻海岸。在实际应用中，必须对泥沙源进行管理。因此，本文以静冈海岸为例，探讨了河流三角洲海岸保护的基本问题，并提出了河流三角洲海岸保护的主要方法。3)方法的应用新泻海岸和长津-绪加特海岸进行了应用。随着新泻海岸海岬的建设，通过数值模拟比较了构筑物、海滩营养和沙滩形成对海滩侵蚀的控制。第三，利用海岬控制海滩侵蚀的方法对于长期稳定沙滩是最有效的。应用该方法和长期海岸线预测模型，建立了一种可能的方法，通过形成稳定的沙滩在六越-绪方海岸稳定沙滩。少

In this research project, a methodology for beach erosion control for the reduction of a river delta was investigated based on the stabilization of sanday coasts in the sedimentation system, as well as their large scale coastal behavior. The main results are summarized as1)Reduction processes of a river delta and its prediction Investigated the reduction process of the river deltaic coasts of the Kurobe, Abe, Fuji, Tenryu rivers, there clearly exist two modes of shoreline changes due to distinct types of erosive wave. The first mode is defined to be an erosive wave propagating down-coast as a diffusion phenomenon, and the second was estimated from the variation from the erosive wave and defined to be an erosive wave propagating down-coast as a wave phenomenon. We conclude that shoreline change due to beach erosion can be described as space-time change propagating down-coast as a diffusion phenomenon, upon which shoreline variation propagates as a wave phenomenon faster than the shoreli … More ne change. The erosive wave of the first mode are subject to changes as positive and negative erosive wave due to the initial and boundary conditions at the river mouth in relation to the sediment input from the river and local change in the river delta. A long-term shoreline change prediction model was established introducing the representative stormy wave and swell. Its application was made to hindcast the long-term shoreline change on the Joetsu-Ogata coast.2)Methodology for beach erosion control Based on the methodology for beach erosion control using headlands and large scale coastal behavior, a methodology for sandy beach stabilization by establishing sandy beaches was investigated. Its application was made to the Niigata coast. Pratically, in the application of the methodology the sediment source management must be made. Therefore, the fundamental problems were investigated referring to the Shizuoka coast, and principal methodology for the preservation of river deltaic coasts were proposed.3)Applications of the methodology Applications were made to the Niigata and Joetsu-Ogat coasts. As the Niigata coast headlands have been being constructed, beach erosion control by structures, beach nourishment, and formation of sandy beaches were compared by numerical simulation. The third one, methodology for beach erosion control using headlands is the most effective for the long-term sandy beach stabilization. Applications of both the methodology and long-term shoreline prediction model were made to establish a possible method for sandy beach stabilization by the formation of stable sandy beaches on the Joetsu-Ogata coast. Less