17:15 〜 19:15
[AHW26-P01] Impacts of shallow landslides on stream chemistry in forested headwater catchments: a case study of the 2018 Hokkaido Eastern Iburi earthquake in Japan
★Invited Papers
キーワード：北海道胆振東部地震、崩壊堆積物、酸化還元反応、水質
Landslide is a natural hazard that can destroy infrastructure and kill people. Recent studies have suggested various effects of landslides on surface and groundwater chemistry. However, much less is known about the effects of shallow landslides on the water chemistry. In this study, the impact of shallow landslides on stream chemistry was investigated in headwater catchments affected by the 2018 Hokkaido Eastern Iburi earthquake in Japan. To this end, the concentrations of redox-sensitive elements dissolved in stream water and seepage from landslide deposits were analyzed. The results showed that the concentrations of several ions in stream water correlated with the percentage of shallow landslide area to the catchment area. In addition, the landslide seepage had lower redox potential (Eh) and concentrations of dissolved O2, NO3−, and SO42− and higher electrical conductivity (EC) and concentrations of dissolved NH4+, Mn2+, and Fe2+ than stream water. The results suggest that highly reducing conditions were formed within the landslide deposits. This also implies that the deposition of landslide masses on valley floors leads to the expansion of waterlogged O2-depleted soil zones, facilitating redox reactions accompanied by the reductions of NO3−, SO42−, Mn4+, and Fe3+. Incorporating the role of landslide deposits on stream and groundwater chemistry may be recommended for robust water resource management in landslide-prone areas.