Increased rainfall associated with climate change can increase sediment discharge. The supply of fine sediment from slope failures inhibits bed armoring of mountain rivers and increases sediment discharge to the downstream reaches. Floods without slope failures lead to bed erosion and armoring and may ultimately decrease sediment discharge. Thus, it is important to consider sediment discharge from slope failure and bed erosion as factors affecting sediment production. Climate change affects not only the rainfall amount, but also the temporal rainfall pattern; consequently, the pattern affects the sediment production factors and the amount of sediment discharge. However, changes in sediment discharge due to climate change based on sediment production sources have not yet been clarified. In this study, we statistically analyzed 1200 results simulated using a physics-based sediment runoff model to assess the impact of changes in temporal rainfall patterns on sediment discharge and sediment production sources in the Pekerebetsu River Basin. In the simulations, we used the rainfall predicted in d4PDF (Database for policy decision-making for future climate change), a large ensemble climate simulation database at 5 km and 20 km resolutions. Our results showed that the climate-driven increase in sediment discharge was considerably larger than that of rainfall. An increase in short-term heavy rainfall increased the supply of fine sediments from slope failure. This resulted in the suppression of bed armoring and a large increase in sediment discharge. Thus, the increase in sediment discharge is not only caused by an increase in rainfall but also by changes in temporal rainfall patterns and sediment production factors. The sediment discharge calculated for the 20 km resolution climate projection was nearly one order of magnitude smaller than that for the 5 km resolution. This suggests that the 20 km resolution climate projections do not adequately represent orographic rainfall in the mountains and thus, do not adequately reproduce extreme sediment discharge events. An increased sediment supply causes bed aggradation and decreases the river conveyance capacity of the downstream channel. The model developed in this study will contribute to flood risk analysis and flood control planning for increased rainfall due to climate change.

与气候变化相关的降雨量增加会增加沉积物排放。斜坡破坏产生的细泥沙的供应抑制了山区河流的河床装甲，并增加了下游河段的泥沙排放。没有斜坡破坏的洪水会导致河床侵蚀和装甲，并可能最终减少泥沙排放。因此，重要的是要考虑斜坡失稳和河床侵蚀造成的泥沙排放作为影响泥沙产生的因素。气候变化不仅影响降雨量，还影响降雨的时间格局；因此，该格局影响产沙因素和排沙量。然而，基于泥沙产生来源的气候变化引起的泥沙排放变化尚未明确。在这项研究中，我们统计分析了使用基于物理的泥沙径流模型模拟的 1200 个结果，以评估降雨模式变化对佩克列别河流域泥沙排放和泥沙产生来源的影响。在模拟中，我们使用了d4PDF（未来气候变化政策决策数据库）中预测的降雨量，d4PDF是一个大型集合气候模拟数据库，分辨率为5公里和20公里。我们的结果表明，气候驱动的泥沙排放量的增加远远大于降雨量的增加。短期强降雨的增加增加了斜坡失稳带来的细粒沉积物的供给。这导致了床层装甲的抑制和沉积物排放的大量增加。因此，泥沙排放量的增加不仅是由于降雨量增加造成的，还与降雨时间模式和产沙因素的变化有关。 20公里分辨率气候预测计算的泥沙排放量比5公里分辨率气候预测计算的泥沙排放量小了近一个数量级。这表明 20 公里分辨率的气候预测不能充分代表山区的地形降雨量，因此不能充分再现极端泥沙排放事件。泥沙供应量增加导致河床淤积，降低下游河道的河流输送能力。本研究开发的模型将有助于针对气候变化导致降雨量增加的洪水风险分析和防洪规划。