ENSEMBLE FLOOD FORECASTING SIMULATION FOR CHIKUMA RIVER FLOOD CAUSED BY TYPHOON HAGIBIS IN 2019

Abstract

 In October 2019, Typhoon Hagibis traveled over eastern Kanto area, provided record-breaking rainfall in the wide area of Kanto and Tohoku regions, resulted in severe flood disasters including Chikuma River. We applied our ensemble flood forecasting method for Chikuma River flood event to investigate the predictability of our system. Our method consists of regional ensemble numerical weather prediction, and Rainfall-Runoff-Inundation (RRI) model for hydrological part. The method could predict the arrival and water level five days before the flood arrival. The forecast simulations of 1.5 to 2.5 days lead-time were in good accuracy with water level error of 1 meter and flood arrival time error within 3 hours. The accuracy of the typhoon track forecasts by JMA global weather forecasts were particularly good in this event resulted in our good ensemble flood forecasting. This result introduced a possibility of an advanced flood forecasting.