[O-05] Stationary linear rain band: its generation mechanism, prediction and disaster mitigation

[O05-04] Predicting rain-induced landslide hazards for disaster mitigation: hydro-geomorphological modeling of hillslopes for building a digital twin of mountainous watersheds

★Invited Papers

*Yuki Matsushi¹ (1.Disaster Prevention Research Institute, Kyoto University)

Keywords:Near-surface critical zone, Process-based modeling, Hazard mapping, Sediment/driftwood yield, Deterministic prediction, Probabilistic assessment

Challenges in hydro-geomorphology are underway to model spatial conditions and hillslope processes leading to rain-induced landslides and sediment/driftwood yield in mountainous watersheds. Weathering zones on hillslopes consisting of weathered bedrock and soil layers, together with ecosystems depending on them, constitute the critical zone between the atmosphere, hydrosphere, lithosphere, and biosphere. The near-surface critical zone in forested humid temperate regions is defined as the boundary layer from the top of the forest canopy to the weathering front of bedrock. In the subsurface part, the weathering zone develops over 10^4 yr by physical and chemical weathering of the bedrock, under external forcing from regional tectonics and glacial-interglacial climate cycles. The topmost soil layer forms in a timescale from 10^2 to 10^3 yr resulting from production and creeping transport of soil particles on hillslopes. Forests including plant root systems in the soil layer grow within 10^2–10^0 yrs. By the rainwater infiltration, fluctuations of pore-water pressure at 10^−1 to 10^−5 yr occurs episodically to trigger shallow landslides and hence sediment and/or driftwood yield from mountainous watersheds. Prediction for location, magnitude, and rainfall threshold for shallow landsliding requires the coupling of the models of the controlling factors at different spatio-temporal scales for building a digital twin of mountainous watersheds to reproduce actual phenomena with the necessary accuracy and precision. This presentation demonstrates an attempt at such hydro-geomorphical modeling and its application toward probabilistic assessment of sediment and/or driftwood yield from mountain watersheds.