Flooding due to torrential rainfall in Kumamoto, 2012

Abstract

Purpose – This study aims to answer the following questions: what is the time scale in which areas downstream are affected by significant rainfall upstream, which areas are first affected, which areas are most affected, how effective is the current warning system in allotting an appropriate amount of time for evacuation, what has been the response time thus far utilizing the current warning system, how can this response time be im-proved using numerical simulation were addressed. The accu-rate prediction of floods and potential inundated areas is crucial for effective flood risk management and this paper analyses the model created for the July 12, 2012 Kumamoto flood event. Design/methodology/approach – Using GIS, LIDAR, SIS and levelling field survey data, the inundated areas were mapped; the sequence of events and the distribution of flood waters were recreated using numerical analysis and modelling. The inundated areas generated by the model were then compared to the actual inundated areas. Findings – The Tatsuda Ichi Chome area was completely inundated within 40 minutes of the first pooling of flood waters, whereas the Tatsuda Jin area was completely inundated within 20 minutes of the initial pooling of flood waters. Originality/value – This research provides empirical evidence of flood impacts and highlights the benefits that can be derived from incorporating accurate flood modelling results into flood risk management systems, as well as extends the methodological approaches of flood risk management.