Kirk here, back again after a long absence. Special thanks to Atsuko for the useful information about Hitoyoshi. I’ll try to pitch in with some news articles. This is from today’s Japan Times:

https://www.japantimes.co.jp/news/2020/07/05/national/seven-confirmed-dead-deluge-hits-southern-japan/

On yesterday’s news I heard that close to 500 millimeters of rain were dumped on parts of Hitoyoshi and on Minamata. These were record numbers for the various locations. 500 millimeters is more than a foot and a half for metric-challenged Americans like me. Just standing in a foot and a half of water is deep enough but when you imagine how water runoff tends to become concentrated in certain spots, I think you can imagine the catastrophic torrents that such rain would cause.