Shirakawa and Midorikawa are quite different; the former, with no tributaries, jets to the sea within concrete banks, while the latter has several tributaries and a large marshland and estuary that has long harbored boats. This has led to a problem of those illegally abandoned, which Kumanichi estimates as about 300, some wooden, some fiberglass, and even a few steel, one of which has been surrounded by an oil fence at the town’s expense.
With rainfall increasing, worries are that these debris can cause serious damage to dikes and bridges during times of flood and also present danger to ships if swept out to Ariake Sea. This Kumanichi article has two good photographs and an interesting map showing the extent of the problem (red lines indicate areas with abandoned boats). The government is working to identify those responsible when possible and countermeasures when not. - William
