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<p>Recent climate change has increased the frequency of heavy rainfall events in Japan, raising concerns about rainfall-induced instability of river levees. Current seepage analyses generally assume that hydraulic properties remain constant with time, although field evidence of time-dependent seepage behavior in full-scale levees remains limited. This study presents approximately three years of field observations on a full-scale test levee constructed in eastern Hokkaido, Japan, a cold region subjected to seasonal freezing and thawing. Water levels and volumetric water content within the levee were monitored during natural rainfall, snowmelt, and artificial rainfall experiments. Laboratory permeability tests on undisturbed samples and in situ permeability measurements were also conducted to examine temporal changes in hydraulic properties. The observations showed that the internal water-level response to rainfall became slower with time. In the 2021 artificial rainfall experiment, the water-level profile progressively developed as accumulated rainfall reached approximately 330&#xa0;mm. Under comparable rainfall conditions, the water-level rise in 2022 was less pronounced than that in 2020 and 2021. In the silty widening layer, average volumetric water content during the non-freezing period decreased by approximately 0.05–0.10&#xa0;m³/m³, dry density increased by approximately 0.1–0.2&#xa0;g/cm³, and saturated hydraulic conductivity decreased by roughly two to three orders of magnitude. These results provide field-based evidence that seepage characteristics of cold-region river levees may change with time after construction, possibly in association with seasonal freeze-thaw processes.</p>

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Field observations of time-dependent seepage behavior in a full-scale river levee under cold-region conditions

  • 期刊论文

  • 发表日期：

    2026年7月27日

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  • Shunzo Kawajiri,
  • Mitsuru Fudo,
  • Tomoyuki Suzuki,
  • Akifumi Hamanaka,
  • Masanori Okushi,
  • Akinobu Ogasawara

摘要

Recent climate change has increased the frequency of heavy rainfall events in Japan, raising concerns about rainfall-induced instability of river levees. Current seepage analyses generally assume that hydraulic properties remain constant with time, although field evidence of time-dependent seepage behavior in full-scale levees remains limited. This study presents approximately three years of field observations on a full-scale test levee constructed in eastern Hokkaido, Japan, a cold region subjected to seasonal freezing and thawing. Water levels and volumetric water content within the levee were monitored during natural rainfall, snowmelt, and artificial rainfall experiments. Laboratory permeability tests on undisturbed samples and in situ permeability measurements were also conducted to examine temporal changes in hydraulic properties. The observations showed that the internal water-level response to rainfall became slower with time. In the 2021 artificial rainfall experiment, the water-level profile progressively developed as accumulated rainfall reached approximately 330 mm. Under comparable rainfall conditions, the water-level rise in 2022 was less pronounced than that in 2020 and 2021. In the silty widening layer, average volumetric water content during the non-freezing period decreased by approximately 0.05–0.10 m³/m³, dry density increased by approximately 0.1–0.2 g/cm³, and saturated hydraulic conductivity decreased by roughly two to three orders of magnitude. These results provide field-based evidence that seepage characteristics of cold-region river levees may change with time after construction, possibly in association with seasonal freeze-thaw processes.