Characterization of flood inundation in Sanjo City, Japan on July 13, 2004

On July 13, 2004, a heavy rainfall hit the Niigata area, resulting in a levee breach in the Ikarashi River. The inundation in the Sanjo City claimed 15 victims and caused huge property damage. The present work conducted analysis on peak discharge and water level variation at the place where the levee was breached. It also carried out flood inundation simulation in order to gain a better understanding of the consequences of the levee failure. It is found that the peak discharge on July 13, 2004 exceeded the full capacity of the river Ikarashi by approximately 20%. Besides, the outflow hydrograph from the breach was estimated for performing inundation simulation. Flood inundation simulation shows that the water spread out through the Sanjo City generally in two directions, and the maximum inundation depth was above 2m.