Abstract
The Nachi Falls in the southern Kii Mountain Range in Japan has been experiencing high water turbidity during heavy rainfall, primarily because of debris from landslides triggered by torrential rain during the severe typhoon Talas in 2011. In recent years, however, the impact of debris on turbidity appears to have sharply declined. At the same time, filamentous algae communities bloomed extensively in the submerged stream channels of the headwater in early 2019 but were undetectable by mid-2019 in the regional climate of humid subtropical type and annual rainfall exceeds 3500 mm.
