Currently covered with grasslands, aerial photographs from the Geographical Survey Institute taken in 1960 and 1977 reveal the presence of 3 to 4 curved former river channels on the north side of the Nakatsugawa River. Unfortunately, no definitive data could be obtained regarding the period prior to the 1820s when Bokushi Suzuki visited. It is reasonable to assume that the water volume and course of the Nakatsugawa River have significantly changed due to the development of agricultural water channels and intakes in the Owaki region, the construction of the Koyasan Dam by Tokyo Electric Power Company, and the extraction of river gravel.
Regarding the rocks forming the current Shimizu Riverbed, no typical river gravel deposits are observed, and the rocks do not show signs of erosion by river water. This suggests that the rapid change in water volume and flow pattern is likely due to the relatively recent collapse and deposition of andesitic pyroclastic rocks, rock debris, and gravel on the riverbed.
012：The Akayamago Village where Bokushi walked
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