Volcanic ash
Volcanic ash fell and widely covered the cultivated fields east of Mount Fuji. To recover the fields farmers cast volcanic products out to dumping-grounds making piles. The rain washed material from the dumping grounds away to the rivers and made some of the rivers shallower, especially into the Sakawa river, into which huge volumes of ash fell, resulting in temporary dams. Heavy rainfall on 7–8 August 1708, the year following the Hōei eruption, caused an avalanche of volcanic ash and mud, breaking the dams and flooding the Ashigara plain.