Temporal and spatial distributions of flood water storage volume of the main river and tributaries in the Ishikari River basin

In recent years, Japan experienced frequent and intense heavy rainfalls, resulting in serious flood disasters in many areas. It is also necessary to control floods in tributaries and basins of these tributaries in addition to flood control of the main river. This will be accomplished by understanding flood formation process in the basins of tributaries as well as the main river. Integrated flood flow analysis for the main river and tributaries was conducted by the use of observed temporal changes in the water surface profiles of the 2016 flood in the Ishikari River, Hokkaido, Japan. Temporal and spatial water storage volume distributions in the Chitose River and Ishikari River basins give a new graphical representative method to visualize that when, where, how much volume of rainfall are stored in each basin, and make it possible to verify effects of flood control measures.