Session1: River Engineering and Management
Title: RESEARCH ON METHODS FOR ANALYZING THE IMPACT OF FLOOD CONTROL FACILITIES ON EXTREME RAINFALL EVENTS
Takehiro Oki, Makoto Nakatsugawa, Thu Nguyen Thanh
In recent years, flood damage attributed to the influence of climate change has been occurring frequently in many parts of the world. Hokkaido Prefecture, Japan, was hit by four tropical storms in August 2016. The basin of the Chitose River, a tributary of the Ishikari River, is greatly affected by the Ishikari River’s backwater for a length of 30 km. The tributaries are also affected by the backwater. Thus, the Chitose River has a high flood risk from heavy rainfall associated with climate change. This study estimates flood damage caused by extreme rainfall associated with climatic changes. The study was conducted in three stages. (1) Extract the rainfall data for large-scale flooding from the Database for Probabilistic Description for Future climate change (d4PDF) as input data of heavy rainfall (external force) associated with climate change. (2) Calculate the discharges of the main river and the tributaries by inputting the basin area and the mean rainfall for each sub-basin into a one-tank storage function model. (3) Estimate the inundation depth using a flood model that incorporates the operations of sluiceways and drainage pump stations, and the development or nondevelopment of 6 retarding basins. The heavy rainfall data due to climate change is applied from the ensemble experiment results (d4PDF) calculated by the Earth Simulator supercomputer. The results of the study can be used to estimate what kind of risks the treatment facility group contains in a comprehensive manner, and to make a multifaceted evaluation for new flood control measures.