The 2003 Hokkaido Hidaka flood : sedimentary processes in the open ocean and influence to sea bottom environments

洪水为海洋环境提供了大量的陆源物质，影响了海底环境和地层的形成。大量沉积物在海底的快速沉积会对海底环境产生影响。由于洪水发生后立即进行的海洋地质和沉积学调查很少，因此对洪水沉积物在海洋环境中的行为和沉积过程的了解并不充分。2003年8月，台风200310带来的暴雨在北海道飞高地区造成了洪水和山体滑坡，大量的沙土被河流带入海洋。我们的调查显示了陆架上的两种洪水泥沙沉积模式。一种是高密度（超螺旋）流的运输。通过这种机构可以实现跨货架的长距离运输。另一种是由浅槽表面羽流形成的。该系统在河口附近沉积了洪水泥。内大陆架海底地形控制着这种运输方式。考虑到外陆架到深海盆地底的洪水泥沙沉积，这次洪水向海洋提供的陆源物质比以往河流观测估计的要多。这些结果验证了高旋流对陆源物质向深海长距离输送的重要性，而洪水对深海物质补给起着重要作用。

Floods supply large amounts of terrigenous materials to marine environments that affects sea bottom environments and strata formation. Quick deposition of large amount of sediments on sea floor may influence to sea floor environments. Because of few marine geological and sedimentological surveys have been conducted immediately after floods, behavior of flood sediments in marine environments and sedimentary processes are not well understood. In August 2003, heavy rain associated with by the typhoon 200310 caused flooding and landslides in Hidaka area, Hokkaido large amount of sand and mud were transported by rivers to ocean. Our survey indicated the two modes of flood mud deposition on the shelf. One is transportation by density (hyperpycnal) flows. Long distance transport across shelf was available by this mechanism. Another is diverse by hypopycnal surface plume. Flood mud was deposited near the river mouth by this system. Inner shelf submarine topography controls such a transportation mode. Taking into account of flood mud deposition on the outer shelf to deep-sea basin floor, the larger amount of terrigenous materials than those previously estimated from river observations were supplied to ocean by this flood. There results verify the importance of the hyperpycnal flow for long-distance transport of the terrigeouns materials to the deep-sea, and flood plays an important role on material supply to deep-sea.