Original Article

Environmental Earth Sciences

, Volume 61, Issue 6, pp 1215-1225

First online:

The impacts of hysteresis on variably saturated hydrologic response and slope failure

  • Brian A. EbelAffiliated withDepartment of Geological and Environmental Sciences, Stanford UniversityU.S. Geological Survey Email author 
  • , Keith LoagueAffiliated withDepartment of Geological and Environmental Sciences, Stanford University
  • , Ronaldo I. BorjaAffiliated withDepartment of Civil and Environmental Engineering, Stanford University

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Abstract

This investigation employs 3D, variably saturated subsurface flow simulation to examine hysteretic effects upon the hydrologic response used to drive unsaturated slope stability assessments at the Coos Bay 1 (CB1) experimental catchment in the Oregon Coast Range, USA. Slope stability is evaluated using the relatively simple infinite slope model for unsaturated soils driven by simulated pore-water pressures for an intense storm that triggered a slope failure at CB1 on 18 November 1996. Simulations employing both hysteretic and non-hysteretic soil–water retention curves indicate that using either the drying soil–water retention curve or an intermediate soil–water retention curve that attempts to average the wetting and drying retention curves underestimates the near-surface hydrologic response and subsequently the potential for slope failure. If hysteresis cannot be considered in the hydrologic simulation, the wetting soil–water retention curve, which is seldom measured, should be used for more physically based slope stability assessment. Without considering hysteresis or using the wetting soil–water retention curve, the potential for landsliding in unsaturated materials may be underestimated and a slope failure could occur when simulations predict stability.

Keywords

Hysteresis InHM Landslide Unsaturated Modeling Hillslope