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陆源物质，影响了海底环境和地层形成。大量沉积物在海底的快速沉积可能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，人们对洪水沉积物在海洋环境中的行为和沉积过程没有很好的了解。2003年8月，200310号台风带来的暴雨在北海道东高地区引发了洪水和山体滑坡，大量沙泥被河流输送到海洋中。我们的调查表明，陆架上有两种洪水淤泥沉积模式。一种是通过密度(超高温)流进行运输。该机构实现了跨货架的长距离运输。另一种是低空表面羽状物的多样性。该系统在河口附近淤积了洪水泥沙。内陆架海底地形控制着这种运输方式。考虑到从外陆架到深海盆地底部的洪水泥浆沉积，这次洪水向海洋提供的陆源物质比以前从河流观测中估计的要多。这些结果验证了超高温流对陆源物质向深海远距离输送的重要性，洪水对深海物质供应起着重要作用。

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.