The aim of this study was to determine the extent to which village residents were able to restore agricultural lands damaged by frequent flooding and the associated deposition of sediments in the Lower Tenryu River basin during the Edo Period. In addition, the development of the shimabatake landforms and their relationship with these periods of flooding was also investigated.
The Tenryu River previously transported considerable amounts of sediment from upstream areas and experienced frequent flooding. Consequently, coastal villages and agricultural areas suffered extensive flood damage when dikes collapsed, and large amounts of sediment were deposited in these areas as the floodwaters receded. This sudden influx of sediments required considerable amounts of time and labor to remove. In the villages of the Lower Tenryu River basin examined in this case study, only a small area of agricultural land had been completely restored one to two years after a flood event. Since the quantities of sediments that were deposited in these areas made physical restoration difficult, and because the excess sediment effectively prevented the cultivation of rice in these areas, the local lords either exempted the affected farmers from having to pay tribute land tax or reduced their contributions. For example, the agricultural lands around Sagisakanakanogou were damaged by extensive sediment deposition after floods in 1845; seven years later in 1852, the restoration of the area had still not been completed and the residents were either fully or partially exempted from having to pay tribute land tax. Interestingly, it is unlikely that there was insufficient labor to restore these areas sooner since the area of land affected was relatively small. It therefore appears that in many cases the inhabitants managed the land with the intention of doing very little restoration work until the tax amnesty period expired.
There was also evidence of areas where residents had initiated restoration work as the period of tax amnesty approached, but the work had not been completed in time. In such cases, residents appear to have decided not to remove the earth, and to convert their paddy fields into dry fields instead. In so doing, they created the shimabatake landscape prevalent in the area.
