<治水>ダムの洪水調節操作と今後の課題

Abstract

平成30年7月豪雨災害では, 西日本を中心とした広い地域で長時間にわたる豪雨が発生し, 各地で記録的な出水が発生した. ダム貯水池の洪水調節操作によって下流河川の水位低減に大きく貢献した流域があった一方で, 長引く洪水調節によりダムの洪水調節容量が満水となる見込みとなり, やむを得ずダムが異常洪水時防災操作を実施した流域もあった. 本稿では, 当該豪雨災害におけるダム治水操作の実施状況を概観し, その効果と課題を分析するとともに, 今後の大規模な出水に向けたこれら課題への対応策の方向性を述べる.

In the torrential rain disaster in July 2018, heavy rain over a long period occurred in a wide area mainly in western Japan, and recorded floods occurred in various places. There was a catchment basin greatly contributing to the reduction of the flood water level of the downstream river by the flood control operation of the dam reservoir. Meanwhile, due to prolonged flood control, the flood control capacity of the dam is expected to be full, and some dams carried out the emergency spillway gate operation at the time of extreme flooding. In this paper, we outline the implementation status of the dam flood control operation in the heavy rain disaster, analyze the effect and problem, and describe the direction of countermeasures for these problems for large-scale flooding in the future.