CHARACTERISTICS OF UNDERGROUND MALL INUNDATION BY FLUSH FLOOD IN SHORT TIME HEAVY RAINFALL

Abstract

Short-time heavy rainfall and high intensity rainfall events have increased in Japan. The rainfall events cause flush floods in urban area. In these floods, some rainwater intruded into underground spaces like a shopping mall and the users faced the danger of underground flooding. Therefore, it is very important to have an emergency plan for flooding. In order to make a plan, manager for underground spaces should know when and from which entrances the rainwater will flow into there. We simulate an inflow discharge by three different profiles of short-time high intensity rainfall using 1D-2D urban flood model and calculated an underground flooding using shallow flow model with structural mesh. It is found that inflow volume, start time of inflow and velocity spread are quite different in the three cases, but location of inflow is almost same. These results indicate that we have to move a quick response to the flush flood by high intensity rainfall.