Sediment budget analysis for large areas in Japan

在日本的许多沿海地区都观察到了严重的侵蚀，部分原因是来自河流流域的沉积物供应减少，部分原因是由于海岸结构造成的沉积物运动中断。通过组织一个覆盖从北海道到日本西部的全国的研究小组，对日本的大面积地区进行了沉积物收支分析。此外，研究领域已扩展到国外。由于介绍整个研究成果很重要，因此将描述一些主要成果。1.根据位于日本本土东北部的仙台海岸线长期调查数据，成功进行了沉积物预算分析。特别是，输沙率的沿岸分布已很好地估计，考虑因素，如泥沙流失到离岸方向和沿岸泥沙运动的中断所造成的离岸防波堤。类似的长期积累 ...更多信息 2.分析了石卷海岸的长期水深资料，以评价沿海岸沿着修建岬的影响。结果表明，除了成濑河口所在的下漂流端外，研究区的海岸形态在最近几年达到了平衡。3.在相模河、大盐户河、瓦塔里河等河口也存在类似的沙嘴入侵问题。为了阐明这一复杂的过程，本文提出了河口断面面积的平衡条件。根据本文开发的基于过程的模型，它表明，平衡条件可以描述由两个无量纲参数表示河流和海岸沉积的相对重要性。模型结果应用于日本河口，其适用性已得到证实。相似模型可用于波浪、流量和潮汐共同作用下河口沉积环境的评价。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