TEMPORAL ELEVATION CHANGES IN THE SHALE BED AND INCREASE IN SCOUR DEPTH WITH SANDBAR DEFORMATION AROUND THE WEIR DURING FLOODS

Abstract

The local scour and the bed degradation during floods are serious factors causing the damage of river structures. For a structure maintenance and management, it is important to understand bedform changes around structures. Recently, two problems concerning river bed variation have been revealed in the Tama River. One is a local scour around river structures. The local scour by the 2007 flood caused damage of bed protection works upstream of Nikaryo Syukugawara weir. Another is the shale bed erosion problems. The shale bed is known to be susceptible to bed degradation. The objectives of this study are to clarify the relation between sandbar shape changes and local scour under the influence of the weir and examine time changes in shale bed elevation by floods.