RIVER BED CHANGE OF THE TOKACHI RIVER IN FLOOD, AUGUST 2003

Abstract

Field observation of bed configuration was conducted during the 2003 August flood at the Tokachi River. Radio controlled boat was used in this measurement. The aim of this observation is to clarify the change of bed topography during flood. It is found that the bar formation becomes unclear and the flow becomes straight along the channel at the neighborhood of peak water level in which the hydraulic condition becomes no bar region. The changing of observed bed configuration during the flood is compared with the result of stability analysis under unsteady flow condition. The general tendencies of bar formation change by the theoretical results agree with field data. However, the theoretical results cannot reproduce the observed bar wavelength.