Hydrological amplification and landscape-resetting sediment pulses: A 45-year baseline evaluation of the 2025 Mataian River landslide-dam event, Taiwan

Study region The Mataian River catchment, a highly fractured and tectonically active alpine watershed located adjacent to the Longitudinal Valley Fault in eastern Taiwan. Study focus This study investigates the 2025 catastrophic landslide-dam event, the largest sub-aerial landslide in Taiwan's history. The research leverages unprecedented datasets: 1) a 45-year baseline (1980–2024) of daily discharge and sediment flux; 2) high-resolution topographic data captured pre- and post-breach; and 3) high-frequency monitoring capturing the real-time propagation and downstream evolution of the outburst flood wave. New hydrological insights for the region 1) Peak breach discharge reached 8800–8860 m³ /s, nearly four times the 100-year flood design capacity; 2) DoD analysis revealed localized bed aggradation up to 13.9 m, with single-event deposition being 1.68 times the cumulative aggradation of the preceding 45 years; and 3) By October 13, 2025, 305.4 million m³ of residual sediment remained stored, with over 80% retained within the source area and dam remnant. Representing over 23 times the comprehensive annual sediment baseline (including suspended and bed load), the gradual remobilization of this colossal source poses an enduring risk of chronic aggradation under Taiwan's hyper-dynamic climate, necessitating a transition to long-term, catchment-scale sediment routing.