Sediment budget analysis for large areas in Japan

在日本的许多沿海地区观测到严重的侵蚀，部分原因是由于河流流域泥沙供应减少，部分原因是由于海岸结构中断了泥沙运动。通过组织一个覆盖从北海道到日本西部整个国家的研究小组，在日本的大片地区进行了沉积物收支分析。此外，研究领域已扩展到国外。由于重要的是要介绍整个研究成果，一些主要的结果将被描述。基于日本大陆东北部仙台海岸的长期岸线调查资料，成功地进行了泥沙收支分析。特别是考虑到泥沙向近海方向的损失和近海防波堤对近海泥沙运动的中断等因素，较好地估计了输沙率的近海分布。对于精确的泥沙收支分析，强烈建议更多的海岸线调查数据。对石卷海岸的长期水深资料进行了分析，以评价沿岸海岬建设的效果。研究发现，除了研究区成濑河河口所在的下漂端外，其他海岸形态均在最近几年达到平衡。由于向河口供应的泥沙减少，可以观察到沙口的严重侵蚀。在相模河、大洋堂河、渡和河等几个河口，也可以看到类似的沙沫入侵问题。为了阐明这一复杂过程，提出了河口断面面积平衡条件。根据本文建立的基于过程的模型，平衡条件可以用两个无量纲参数来描述，表明河流和海岸沉积的相对重要性。将模型结果应用于日本河口，验证了模型的适用性。类似的模拟将有助于估算波浪、河流流量和潮汐共同影响下的河口沉积环境。少

Severe erosion has been observed in many coastal area in Japan, partly due to reduction of sediment supply from river basin, and partly due to interruption of sediment movement due to coastal structures. Sediment budget analysis has been carried out for large areas in Japan, by organizing a research group covering whole of the country from Hokkaido to the western part of Japan. Furthermore, the research area has been extended to foreign country. Since it is important to introduce whole of the research results, some of the primary results will be described.1.Based on long-term shoreline survey data on Sendai Coat located in northeast of the main land in Japan, sediment budget analysis has been carried out successfully. Especially, longshore distribution of sediment transport rate has been well estimated by considering factors such as sediment loss into the offshore direction and interruption of longshore sediment movement caused by offshore breakwaters. Similar long-term accumulation of … More shoreline survey data is highly recommended foe precise sediment budget analysis.2.Long-term bathymetric data on Ishinomaki Coast has been analyzed for evaluating effect of headlands construction along the coast. It is found that the coastal morphology reached its equilibrium in the very recent years, except the down drift end of the study area where the mouth of the Naruse River is located. Due to the reduction of the sediment supply to the mouth, severe erosion of the sand spit can be observed.3.Similar problem of sand spit intrusion can be seen at several river mouths such as Sagami, Ohyodo and Watari Rivers. In order to clarify such a complicated processes, equilibrium condition for cross sectional area at a river entrance. According to the process-based modeling developed herein, it is shown that the equilibrium condition can be described by two dimensionless parameters indicating relative importance of river and coastal sedimentations. The model results are applied to river mouths in Japan, and its applicability has been confirmed. Similar modeling will be useful for estimating sedimentary environment at a river mouth under combined influence of waves, river discharge and tides. Less