Author(s): So Kazama; Kota Chiba

Linked Author(s): So Kazama

Keywords: Flood; Evapotranspiration; Vegetation change; Low flow

Abstract: The distributed hydrological runoff model was applied three basins assuming that the land use of the basin will eventually change to forest when the population becomes zero. Additionally, a river channel covered with vegetation and residential area changed to forest were assumed. Changes in the annual maximum discharge, high water discharge (74% percentile discharge), and low water discharge (25% percentile discharge) were investigated for the current land use and the land use with the entire area as forest. The target basins are three small river basins of about 100 km2 in Japan, where depopulation is progressing. When the land use was changed, the annual maximum discharge of the Ohtani River decreased by 2.71%, and the high and low water discharges increased by 2.71% and 1.99%, respectively. Decrease in annual maximum discharge reduces flood risk and mitigate downstream damage. The increase in high and low water flow stabilizes the water flow in the catchment area and promotes the supply of abundant water resources. The annual maximum discharge at Sukawa River decreased by 2.89%, and the high and low water discharges increased by 3.06% and 1.65%, respectively. On the other hand, the maximum annual runoff at Dangosawa increased by 1.19%, and the high and low runoff decreased by 1.82% and 0.86%, respectively. From the above, the change of land use to forest is expected to have a positive impact of flood and drought in such depopulation basins. Fluctuations due to changes of discharge in evapotranspiration change alone are small changes of 10-5% to 10-2% in all basins.

DOI: https://doi.org/10.3850/978-90-833476-1-5_iahr40wc-p0170-cd

Year: 2023