Sediment control and logs capturing in sand pocket with combination of sabo dam with large conduit and iron bars

Abstract

In the Otoishi River, a tributary on right side of the Akatani River in the Chikugo River basin, a large amount of sediment and woody debris were deposited on riverbed due to the sediment disaster caused by the heavy rainfall in northern part of Kyushu Region on 5th to 6th July in 2017. As one of countermeasures to control the outflow of sediment and woody debris to the Akatani River, a sand pocket is planned with the sabo dam with large conduit parts and the log broom works. In this study, hydraulic model test and flume test were carried out to obtain knowledges for design of the sand pocket. Iron bars are installed vertically at the upstream front of the large conduit parts for capturing sediment and logs, and those intervals are desirable to be set in consideration of sediment diameter and sediment movement without the dam. Besides, it is necessary to consider capturing function and flow characteristics such as shockwave when the log broom works is planned in setting of layout and dimensions.