Kana OOIGAWA

A Study of the Difference among Several Basin-Averaged Rainfall Intensities on the Heavy Rain, Using Radar Data Corrected with Ground Observations

Toshirou KUMAKURA

A heavy rainfall was observed in Niigata and Fukushima prefectures from July 12 to 13, 2004. 11 banks were destroyed and 15 people died near basins of Ikarashi and Kariyata rivers. A number of damaged buildings in Fukushima was about one hundreds compared with the number in Niigata, though past records of a daily rainfall were broken at several observatories in Fukushima as same as in Niigata. Firstly, we obtained a horizontal distribution of gridded rainfall data observed with radar, which were corrected by the rainfall data observed on the ground. Secondly, the basin-averaged rainfall data were calculated in the basins along Ikarashi river (BI) and Tadami river (BT). We found that the averaged rainfall intensity in BT was 34% smaller than that in BT, and the gradient of the rainfall intensity in 3 hours before the time observed the maximum intensity in BT was 60% smaller than the gradient in BI. Those resulted in the different magnitude of the building-damage between BT and BI.