Environmental Geology

, Volume 55, Issue 6, pp 1269–1277 | Cite as

Numerical modeling of rainstorm-induced shallow landslides in saturated and unsaturated soils

  • Tung-Lin TsaiEmail author
  • Hung-En Chen
  • Jinn-Chuang Yang
Original Article


For the assessment of shallow landslides triggered by rainfall, the physically based model coupling the infinite slope stability analysis with the hydrological modeling in nearly saturated soil has commonly been used due to its simplicity. However, in that model the rainfall infiltration in unsaturated soil could not be reliably simulated because a linear diffusion-type Richards’ equation rather than the complete Richards’ equation was used. In addition, the effect of matric suction on the shear strength of soil was not actually considered. Therefore, except the shallow landslide in saturated soil due to groundwater table rise, the shallow landslide induced by the loss in unsaturated shear strength due to the dissipation of matric suction could not be reliably assessed. In this study, a physically based model capable of assessing shallow landslides in variably saturated soils is developed by adopting the complete Richards’ equation with the effect of slope angle in the rainfall infiltration modeling and using the extended Mohr–Coulomb failure criterion to describe the unsaturated shear strength in the soil failure modeling. The influence of rainfall intensity and duration on shallow landslide is investigated using the developed model. The result shows that the rainfall intensity and duration seem to have similar influence on shallow landslides respectively triggered by the increase of positive pore water pressure in saturated soil and induced by the dissipation of matric suction in unsaturated soil. The rainfall duration threshold decreases with the increase in rainfall intensity, but remains constant for large rainfall intensity.


Shallow landslide Saturated and unsaturated soils Rainstorm 

List of symbols


the change in volumetric water content per unit change in pressure head


the minimum value of C


effective cohesion


\({K_{s}} \mathord{\left/{\vphantom {{K_{s}} {C_{0}}}} \right.\kern-\nulldelimiterspace} {C_{0}}\)


water depth


slope depth


factor of safety


rainfall intensity


saturated hydraulic conductivity


hydraulic conductivity in lateral direction (x and y)


hydraulic conductivities in slope–normal direction (z)


the degree of saturation


fitting parameter


fitting parameter


rainfall duration


pore air pressure


pore water pressure


the coordinates


total normal stress


groundwater pressure head


soil volumetric water content


saturated moisture content


residual moisture content


slope angle


effective friction angle


the friction ϕ angle with respect to the matric suction


fitting parameter


the unit weight of soil


the unit weight of water


  1. Anderson MG, Howes S (1985) Development of application of a combined soil water-slope stability model. Q J Eng Geol London 18:225–236CrossRefGoogle Scholar
  2. Baum RL, Savage WZ, Godt JW (2002) TRIGRS—a Fortran program for transient rainfall infiltration and grid-based regional slope-stability analysis, Virginia, US Geological Survey Open file report 02–424Google Scholar
  3. Bear J (1972) Dynamics of fluids in porous media. Dover, MineolaGoogle Scholar
  4. Borga M, Fontana GD, De Ros D, Marchi L (1998) Shallow landslide hazard assessment using a physically based model and digital elevation data. Environm Geol 35:81–88CrossRefGoogle Scholar
  5. Collins BD, Znidarcic D (2004) Stability analyses of rainfall induced landslides. J Geotech Geoenviron Eng 130(4):362–372CrossRefGoogle Scholar
  6. Crosta GB, Frattini P (2003) Distributed modeling of shallow landslides triggered by intense rainfall. Nat Haz Earth Syst Sci 3:81–93Google Scholar
  7. D’Odorico P, Fagherazzi S, Rigon R (2005) Potential for landsliding: dependence on hyetograph characteristics. J Geophys Res Earth Surf 110(F1)Google Scholar
  8. Escario V, Saez J (1986) The shear strength of partly saturated soils. Geotechnique 36:453–456CrossRefGoogle Scholar
  9. Frattini P, Crosta GB, Fusi N, Negro PD (2004) Shallow landslides in pyroclastic soil: a distributed modeling approach for hazard assessment. Eng Geol 73:277–295CrossRefGoogle Scholar
  10. Fredlund DG, Morgenstern NR, Widger RA (1978) The shear strength of unsaturated soils. Can Geotech J 15:313–321CrossRefGoogle Scholar
  11. Hills RG, Hudson DB, Wierenga DB (1989) Modeling one-dimensional infiltration into very dry soils 1. Model development and evaluation. Water Resour Res 25:1259–1269CrossRefGoogle Scholar
  12. Hsu SH, Ni CF, Hung PF (2002) Assessment of three infiltration formulas based on model fitting on Richards’ equation. J Hydrol Eng 7(5):373–379CrossRefGoogle Scholar
  13. Hurley DG, Pantelis G (1985) Unsaturated and saturated flow through a thin porous layer on a hillslope. Water Resour Res 21:821–824CrossRefGoogle Scholar
  14. Iverson RM (2000) Landslide triggering by rain infiltration. Water Resour Res 36:1897–1910CrossRefGoogle Scholar
  15. Keim RF, Skaugset AE (2003) Modelling effects of forest canopies on slope stability. Hydrol Process 17:1457–1467CrossRefGoogle Scholar
  16. Lan HX, Lee CF, Zhou CH, Martin CD (2005) Dynamic characteristics analysis of shallow landslides in response to rainfall event using GIS. Environ Geol 47:254–267CrossRefGoogle Scholar
  17. Montgomery DR, Dietrich WE (1994) A physically based model for the topographic control on shallow landslide. Water Resour Res 30:83–92Google Scholar
  18. Morrissey MM, Wieczorek GF, Morgan BA (2001) A comparative analysis of hazard models for predicting debris flows in Madison County, Virginia. US Geological Survey Open file report 01–67Google Scholar
  19. Richards LA (1931) Capillary conduction of liquids in porous mediums. Physics 1:318–333CrossRefGoogle Scholar
  20. Tarantino A, Bosco G (2000) Role of soil suction in understanding the triggering mechanisms of flow slides associated with rainfall. In: Wieczorek GF, Naeser ND (eds) Debris-flow hazards mitigation: mechanics, prediction, and assessment, pp 81–88Google Scholar
  21. Tsai TL (2007) The influence of rainstorm pattern on shallow landslide. Environ Geol (in press)Google Scholar
  22. Tsai TL, Yang JC (2006) Modeling of rainfall-triggered shallow landslide. Environ Geol 50(4):525–534CrossRefGoogle Scholar
  23. Van Genuchten (1980) A closed-form equation for predicting hydraulic conductivity of unsaturated soils. Soil Sci Soc Am J 44:892–898CrossRefGoogle Scholar
  24. Wallach R, Grigorin G, Rivlin J (1997) The errors in surface runoff prediction by neglecting the relationship between infiltration rate and overland flow depth. J Hydrol 200:243–259CrossRefGoogle Scholar
  25. Wu W, Slide RC (1995) A distributed slope stability model for steep forested basins. Water Resour Res 31:2097–2110CrossRefGoogle Scholar

Copyright information

© Springer-Verlag 2007

Authors and Affiliations

  1. 1.Department of Civil and Water Resources EngineeringNational Chiayi UniversityChiayi CityTaiwan
  2. 2.Department of Civil EngineeringNational Chiao Tung UniversityHsinchu CityTaiwan

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