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A huge flood disaster was caused by a heavy rainfall around the Chuetsu area of Niigata Prefecture on July 13, 2004. The flood breached the levees in many places along Ikarashi-, Kariyata-, and Chigoshimizu Rivers, so that many houses were swept away and wide areas were under muddy flood water in Sanjo and Mitsuke Cities and Nakanoshima Town.In this study, we describe the damages sustained by the flood in Nakanoshima Town area and the southern area of Mitsuke City along Kariyata River, and discuss the current processes of the flood at these areas. It is clear that a surge of the flood attacked houses near by the point of levee breach at Nakanoshima Town, judging from the evidences such as the directions of scours and the traces of flood current toward the houses. The preferred orientations of inclined or fell -down houses , traffic signs, fens, etc., indicated the direction change of flood current. Though the primary surge ran powerfully toward southwest, the flood flowed westward being led to the lower topography until the direction changed toward northwest by an obstruction of natural levee. On the other hand, in the southern area of Mitsuke City, the flood current direction was restricted so much by the narrow valley plain that its flood strength increased much more. As the levee of Chigoshimizu River also breached, the older levee, which remained between the present one and fluvial terrace, was collapsed immediately. The flood current did not only lose its power when it had reached at the lowest terrace but also run up beyond the terrace and destroyed some houses standing on it.

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