Assessment of Climate Change Impact on Sediment Runoff and Sediment-Related Hazards Employing Integrated Simulation of Sediment Production and Runoff.

Under the background of enrichment of the precipitation database, which is based on the climate change projection, future-change projection of flood risk is already developing. However, when we focus on the sediment-related hazard on a watershed scale, sediment production and transport in the catchment should be carefully treated. In this description paper, firstly, we introduce the structure of the simulation model SiMHiS, composed of a sediment production and supply model based on landslide prediction, rainfall infiltration and runoff, and sediment transport in the channel system. Secondly, we introduce a future-projection result in the Akatani River watershed in Northern Kyushu Island, Japan, damaged by heavy rainfall in 2017. Maximum water discharge, total volume of sediment discharge, maximum water level, and maximum riverbed level at specific locations are selected as indicators for the assessment. For the rainfall data, local extreme values of heavy rainfall data that occurs in northern Kyushu during the rainy season were given to the simulation to evaluate the future change of the extreme event by using the limited period of the dataset. The results showed a clear increasing trend for all indexes, indicating that phenomena of a scale that does not occur in the current climate might occur. We also discussed the possibility of statistical and quantitative evaluation in future studies using our method with the precipitation dataset, which has finer spatiotemporal resolution and a more extended period. [ABSTRACT FROM AUTHOR]