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<p>Woody debris flows (WDFs) are among the most destructive compound geohazards in forested mountainous regions. The large volume of woody debris can rapidly induce blockage and sedimentation in Open-type check dams, significantly increasing the risk of structural failure. Slit check dams (SCDs) are a type of open-check dam reported to mitigate WDFs, but their regulatory mechanisms remain unclear. In this study, a series of physical model experiments was conducted to investigate the effects of relative opening ratio, woody debris length and content, and debris flow bulk density on opening clogging characteristics and mitigation performance. The results indicate that the interception process of WDFs by SCDs can be divided into five dynamic evolutionary stages: initial interception, flow runup and climbing, temporary clogging by woody debris, crest overflow, and impoundment with gradual drainage. Woody debris interception significantly increases the probability of opening blockage inducing four distinct blockage states: unobstructed, partially obstructed, fully obstructed, and supercritical blockage. Based on the relative opening ratio (<i>b/d</i><sub><i>max</i></sub>), three functional mitigation zones are identified: interception-dominated zone (<i>b/d</i><sub><i>max</i></sub> ≤ 1.5), interception–retention cooperative regulation zone (1.5 &lt; <i>b/d</i><sub><i>max</i></sub> &lt; 4.0), and flow-regulation zone (<i>b/d</i><sub><i>max</i></sub> ≥ 4.0). The blockage ratio and mitigation indices decrease progressively with increasing opening ratio. Under different experimental conditions, the woody debris interception ratio (W) ranged from 40.1% to 99.2%, while the discharge reduction ratio ranged from 10.8% to 84.2%. Furthermore, an improved integrated blockage criterion (<i>F</i><sub>d</sub>) was proposed by comprehensively incorporating opening geometry, woody debris characteristics, and debris flow properties. A quantitative blockage classification standard was subsequently established based on <i>F</i><sub>d</sub>. Nonlinear relationships between <i>F</i><sub>d</sub> and multiple mitigation indices were further derived, enabling quantitative prediction of blockage development and mitigation performance of SCDs under WDF conditions. The results provide new insights into the blockage-regulation mechanisms of SCDs and offer theoretical support for the optimized design of open-type check dams in forested mountainous regions.</p>

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Regulation mechanisms of woody debris flows by slit check dams

  • 期刊论文

  • 发表日期：

    2026年7月1日

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  • Yuqi Shang,
  • Jinfeng Liu,
  • Hao Sun,
  • Dongwei Wang,
  • Wentao Zhang,
  • Huaquan Yang

摘要

Woody debris flows (WDFs) are among the most destructive compound geohazards in forested mountainous regions. The large volume of woody debris can rapidly induce blockage and sedimentation in Open-type check dams, significantly increasing the risk of structural failure. Slit check dams (SCDs) are a type of open-check dam reported to mitigate WDFs, but their regulatory mechanisms remain unclear. In this study, a series of physical model experiments was conducted to investigate the effects of relative opening ratio, woody debris length and content, and debris flow bulk density on opening clogging characteristics and mitigation performance. The results indicate that the interception process of WDFs by SCDs can be divided into five dynamic evolutionary stages: initial interception, flow runup and climbing, temporary clogging by woody debris, crest overflow, and impoundment with gradual drainage. Woody debris interception significantly increases the probability of opening blockage inducing four distinct blockage states: unobstructed, partially obstructed, fully obstructed, and supercritical blockage. Based on the relative opening ratio (b/dmax), three functional mitigation zones are identified: interception-dominated zone (b/dmax ≤ 1.5), interception–retention cooperative regulation zone (1.5 < b/dmax < 4.0), and flow-regulation zone (b/dmax ≥ 4.0). The blockage ratio and mitigation indices decrease progressively with increasing opening ratio. Under different experimental conditions, the woody debris interception ratio (W) ranged from 40.1% to 99.2%, while the discharge reduction ratio ranged from 10.8% to 84.2%. Furthermore, an improved integrated blockage criterion (Fd) was proposed by comprehensively incorporating opening geometry, woody debris characteristics, and debris flow properties. A quantitative blockage classification standard was subsequently established based on Fd. Nonlinear relationships between Fd and multiple mitigation indices were further derived, enabling quantitative prediction of blockage development and mitigation performance of SCDs under WDF conditions. The results provide new insights into the blockage-regulation mechanisms of SCDs and offer theoretical support for the optimized design of open-type check dams in forested mountainous regions.