COMPARATIVE CONSIDERATION OF HORIZONTAL AND VERTICAL EVACUATION RISKS ALONG THE TIME LINE AROUND THE LEVEE BREACH

Abstract

 In Japan, evacuation advisories are simultaneously issued for a wide area when there is a risk of river flooding. But in the U.S., if there is not enough time to evacuate, they will not issue evacuation orders in some cases. This study focused on the middle basin of the Chikugo River and analyzed inundation situations and lead times to determine the evacuation considering the risk of a horizontal evacuation to a evacuation site versus the risk of remaining in a vertical evacuation at home. Then, we examined the appropriateness of making a "recommendation for vertical evacuation" rather than a uniform evacuation advisory. As a result, the risks of horizontal and vertical evacuation vary greatly in each area, and if there is not enough time to evacuate, it is safer to stay home instead of evacuating to a evacuation site. It is necessary to select appropriate evacuation actions for each area.This study shows that vertical evacuation advisory should be issued in some areas instead of uniformly encouraging horizontal evacuation.