ESTIMATION OF INUNDATION DEPTH DISTRIBUTIONS BY ASSIMILATING LOCAL FLOOD INFORMATION –VALIDATION FOR THE KINU RIVER FLOOD CASE IN SEPTEMBER 2015–

Abstract

 This paper examines the effect of inundation mapping utilizing local flood information obtained in Joso city and the surrounding area, which were damaged by the Kanto-Tohoku torrential rainfall in September 2015. The mapping method assimilates a number of preliminary conducted inundation simulation results and flood-related information from the locals. The authors compare four different scenarios of local information acquisitions and two scenarios without the data assimilation. The result indicates that a more effective assimilation method for getting better mapping of inundation is to measure higher inundation depths, which take place along small tributary rivers, comparing with another method to measure relatively lower inundation depths at designated evacuation shelters. In addition, the accuracy of inundation depth distributions can be improved by assimilation even with fragmented and uncertain information, compared to a case without the assimilation and simply selecting a preliminary conducted inundation estimate.