Sediment Transport Processes under Extreme Rainfall Events Using Dynamic Downscaling Climate Change Projections

Abstract:

Extreme typhoon rainfall events are increasing in Taiwan as a result of climate change. These events have induced extreme sediment transport in channel bed in recent years. This study used dynamic downscaling climate change data to (1) evaluate the extreme river aggradation and the sediment transfer processes under the worst historical conditions and projections for the late 21^st century, and (2) change the extreme discharge to discuss the interaction on different flow intensities and sediment transfer processes by CCHE2D for the downstream of Gaoping River in southern Taiwan. The results show that the sediment aggradation in the historical period is 14 × 10⁶ m³; instead, the sediment variation in the late 21^st century is reduced by 15% compared to the historical period. Artificial structures play import roles in advancing sediment deposition and aggradation control in the Gaoping River. In addition, when peak flow discharges exceed threshold discharge, 10-yr return period discharge, and severe aggradation will occur in the Gaoping River bed (Figure 1). The bed changes will become gentler as the peak discharge increases. It indicates that extreme floods induce relatively severe degradation and significant floods will carry out relative aggrades in the whole Gaoping River bed. These findings assist in understanding the bed change processes under extreme typhoon rainfall events using dynamic downscaling climate change data.