Behavior of fine sediment and its effect on the formation of hypoxia in estuaries.

在传统的河道整治工程手册中，以普通河道作为规划的标准对象，并没有提及下游河口部分的特殊方面。本研究针对未来河道整治工程标准的改革，对一些水力特征不同的河流下游进行了河口细沉积相关水力因素的研究。利用声波湍流测量等最新测量技术，对Tone River河口盐楔中细泥沙的悬浮量进行了测量，并对细泥沙对盐楔头部缺氧形成的影响进行了估计。在北上河入流的欧帕湾，通过野外观测和卫星影像分析，研究了含大量细泥沙的河流淡水对海湾水质的影响。通过野外实测和数值模拟，研究了高濑河河口浅层地形，特别是浅层细沙沉积对海水入侵的影响。

In conventional manuals for river improvement works, in which ordinary river channels are taken as a standard object of planning, do not refer to the special aspects of the estuarine part of downstream reaches. In this research, aiming the future reform of the standard of river improvement works, hydraulic factors related to the fine sedimentation in estuaries are investigated in downstream reaches of some rivers whose hydraulic characteristics are different from one another.In Tone River Estuary, suspension of fine sediment was measured in the salt wedge by using some up-to-date measurement techniques including acoustic turbulence measurement, and the effect of fine sediment on the formation of hypoxia in the head of salt wedge was estimated. In Oppa Bay, where Kitakami River flows in, the deterioration of bay water by the effect of river freshets containing a lot of fine sediment was investigated through field observation and satellite image analysis. In Takase River Estuary, the effect of bed topography, especially of shallow area made by the deposition of fine sediment, on the salt water intrusion was estimated by field measurements and numerical simulation.