ABSTRACT Traditional annual‐scale assessments obscure the dynamic recharge of debris‐flow provenances during concentrated rainy seasons. To address this, the spatiotemporal heterogeneity of monthly soil erosion during the rainy seasons (2022–2023) within debris flow‐prone gullies of the upstream Min River Basin was quantitatively evaluated using the RUSLE framework. During the rainy seasons, the mean monthly soil erosion modulus (SEM) reached 206.0 t ha −1 m −1 in 2022 and 153.3 t ha −1 m −1 in 2023. Spatially, severe erosion (> 12.5 t ha −1 m −1 ) was predominantly concentrated on high‐elevation ridges (e.g., Dengxi and Qipan gullies) and the hanging walls of seismogenic faults. Temporally, erosion exhibited extreme intraannual variability driven by precipitation shifts; notably, intense late‐season rainfall in September 2023 triggered catastrophic erosion surges in Zhangjiaping and Niujuan gullies, peaking at 259.8 and 262.1 t ha −1 m −1 , respectively. Additionally, the underlying physical mechanisms driving bank slope instability were elucidated. First, extreme disturbances dismantle the vegetative shield, causing a critical loss of root‐soil reinforcement against surface scouring. Second, the intrinsic fragility of the clay‐deficient soil matrix facilitates rapid infiltration and elevated pore water pressures, triggering structural mass slumping. Furthermore, SEM was positively correlated with sediment connectivity ( r = 0.32) and bulk density ( r = 0.38), and negatively correlated with soil depth ( r = −0.69) and available water capacity ( r = −0.69). These morpho‐edaphic factors form a self‐reinforcing positive feedback loop: enhanced sediment connectivity accelerates topsoil evacuation, exposing denser subsoils, restricting water capacity, and amplifying aggressive surface runoff. The research can provide a rigorous scientific foundation for targeted geohazard mitigation and watershed management in mountainous regions.
Wang et al. (2026) studied this question.