Arakawa River (and Takiya) in flood

Arakawa River stage hydrograph (updated 6/29)

Yesterday's heavy rain did indeed cause the Arakawa River to flood dramatically. Water levels rose from about 1m to over 5m, and nearly hit the high mark of 5.95m reached during the big flood of July 2004, which brought much destruction and damage to Niigata Prefecture.

Today more heavy rain is causing water levels to rise again! Looking at the precipitation data for the Arakawa River basin above the Odo gauging station (see Tochikura and Gomisawa in links panel) we see that about 300mm has fallen since yesterday morning, with maximum intensities of 10mm/10 minutes (equivalent to 60mm/h). This is an extraordinary amount of rainfall, approaching the daily amounts recorded in Kyushu last week. When the seasonal rain front runs into steep mountain relief we can get these record amounts of rainfall.

If only I had real-time water level data for Takiya! Like the Arakawa River, Takiya River must also be in a major flood. Looking at the Miomote and Takane precipitation data (see links panel) I calculate that 212mm and 283mm respectively has fallen in the last 36 hours, with intensities up to 42 mm/h. Here is yesterday's rainfall data for Takane compared to large flood events which occurred in 2004 and 2005:

Precipitation and Takiya peak stage:
2011/06/23 daily 230mm, max. 42mm/h, peak stage 2.126m (updated 6/29)
2005/08/11 daily 289mm, max. 63mm/h, peak stage 2.590m
2005/06/27 daily 183mm, max. 37mm/h, peak stage 2.145m
2004/07/17 daily 180mm, max. 48mm/h, peak stage 2.302m

Takiya River photos:

Taken 4 days after 2004/07/17 flood

Taken 4 days after 2005/08/11 flood

Honma san shows peak stage for 2005/08/11 flood