Sediment-related disasters caused by heavy rain in July 2018 in Okayama Prefecture, Japan

Abstract

Heavy rains in July 2018 caused several slope failures and debris flows in Okayama Prefecture, Japan ; this was the largest rainfall event to have occurred in Okayama within the past fifty years. As a result, rather than a single remarkable sediment-related disaster in a concentrated area, disasters occurred widely throughout the prefecture during this event.Many local governments on July 6 announced information on sediment-related disasters. Despite this effort, many people were affected by these disasters within their own homes. Thus, although there was sufficient time for evacuation, many people chose not to evacuate, demonstrating that there are substantial problems nonstructural measures for sediment-related disasters.In this report, we describe five sediment-related disasters and they related to regional characteristics of Okayama Prefecture, as well as evacuation efforts during these disasters and their problem.