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<p>On 7 August 2025, an extreme rainfall event impacted Yuzhong County, Gansu Province, China, triggering cascading hazards in the Hongzhuangzi Gully, including flash floods, widespread shallow landslides, the formation of a temporary channel-blocking dam (CBD), and a subsequent debris flow. UAV photogrammetry, high-resolution satellite imagery, rainfall records, and field surveys were integrated to reconstruct the event’s four-stage evolution. A total of 120 shallow landslides were identified, mainly on 25–35° slopes with east to southeast aspects, with failure depths mostly less than 0.6 m. These landslides were concentrated in areas where thin colluvium overlies bedrock, suggesting a possible link to slope hydrological responses under extreme rainfall conditions. In the mid-gully reach, dense plantation forests and a natural constriction may have contributed to temporary blockage by facilitating the accumulation of woody debris and sediment. Geomorphic indicators including mud lines up to 4.5 m high, upstream boulder clusters, asymmetric bank erosion, and a downstream debris fan provide indirect evidence supporting the formation and subsequent failure of a temporary CBD. RAMMS simulations, calibrated against field observations, estimate a total debris-flow volume of approximately 1.105 × 10⁶ m<sup>3</sup>, with about 82% sourced from channel erosion. These findings highlight the need to consider multi-hazard interactions involving ecological factors (e.g., plantation forests) under extreme rainfall conditions, thereby improving the identification and early warning of cascading hazards in mountainous regions.</p>

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Cascading hazards triggered by the 7 August 2025 extreme rainfall in Hongzhuangzi Gully, Gansu, China

  • 期刊论文

  • 发表日期：

    2026年4月8日

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  • Pinliang Li,
  • Jianuo Liu,
  • Qiang Xu,
  • Chuanhao Pu,
  • Jianlong Cheng,
  • Mingli Li,
  • Ming Chang,
  • Pengcheng Xu,
  • Xiaoying Pu,
  • Xiujun Dong,
  • Yateng Meng

摘要

On 7 August 2025, an extreme rainfall event impacted Yuzhong County, Gansu Province, China, triggering cascading hazards in the Hongzhuangzi Gully, including flash floods, widespread shallow landslides, the formation of a temporary channel-blocking dam (CBD), and a subsequent debris flow. UAV photogrammetry, high-resolution satellite imagery, rainfall records, and field surveys were integrated to reconstruct the event’s four-stage evolution. A total of 120 shallow landslides were identified, mainly on 25–35° slopes with east to southeast aspects, with failure depths mostly less than 0.6 m. These landslides were concentrated in areas where thin colluvium overlies bedrock, suggesting a possible link to slope hydrological responses under extreme rainfall conditions. In the mid-gully reach, dense plantation forests and a natural constriction may have contributed to temporary blockage by facilitating the accumulation of woody debris and sediment. Geomorphic indicators including mud lines up to 4.5 m high, upstream boulder clusters, asymmetric bank erosion, and a downstream debris fan provide indirect evidence supporting the formation and subsequent failure of a temporary CBD. RAMMS simulations, calibrated against field observations, estimate a total debris-flow volume of approximately 1.105 × 10⁶ m3, with about 82% sourced from channel erosion. These findings highlight the need to consider multi-hazard interactions involving ecological factors (e.g., plantation forests) under extreme rainfall conditions, thereby improving the identification and early warning of cascading hazards in mountainous regions.