AN EMPIRICAL STUDY ON INUNDATION IN AKITA CITY CENTER AREA, CAUSED BY THE TORRENTIAL RAINFALL IN JULY, 2023

Abstract

 Inundation in the Akita city center area, caused by the torrential rainfall in July, 2023 is substantiated through the observation data on the rainfall and water level in rivers, field survey data on the maximum level of trace of inundation water and inundation water depth, and analysis of fixed point camera images. As the result, it is clarified that (1) the inundation in the city center area is significantly affected by the inundation water flowing in from the Myoden underpass, that is, the ratio of total discharge passed the Myoden underpass to the total amount of rainfall in the city center area is significantly large, (2) the inundation water outstandingly flows along low-lying streets of which some are waterways in the past, (3) the scale of the inland inundation exceeds that caused by the prospective rainfall of 150 mm/h (once every 1, 000 years or so), announced by Akita city, and (4) the maximum level of trace of inundation water and water depth in the district of Narayama Nobori machi are not a little affected by the tide. Issues to be examined from the viewpoint of flood control in the city center area are also indicated.