九州北部豪雨における寺内ダムへの流木流入の実態とダム下流に対するその意義

Abstract

By the heavy rain in the northern part of Kyushu in July 2017, many rivers in the Chikugo River sys-tem were flooded and caused serious damage. In the Sata River located in the middle basin of the Chikugo River system, a large amount of driftwood flowed into the Terauchi dam due to the intensive flood. If driftwood had flowed into the downstream and had been clogged by the bridge piers, the Sata River might have overflowed in wide area near the bridges. Actually, there was little damage in the down-stream area because Terauchi dam had effects of flood control and driftwood trapping. In this study, the quantitative estimating method was developed by using the image processing software, Image J, to esti-mate driftwood volume and sizes over the reservoir area. In addition, the influence of driftwood trapping by the Terauchi dam on the downstream flood damage reduction was estimated by using two-dimensional hydraulic TELEMAC-2D model.