The main aim of the paper was estimation of shear strength parameters of soil from one landslide located in Szymbark near Gorlice using back-analysis method. Shallow landslide located on Wiatrówki slope (Beskid Niski Mts.) was the object of analysis. The landslide was located on the border of agricultural terrace and it was induced by very intense rainfall. Causes of location of analyzed landslide in specific part of terrace were also considered in the paper. Slope stability calculations were made using Spencer’s method. The methodology of back-analysis was done according to recommendations of Duncan and Wright [2005] which allow to obtain one pair of values of internal friction angle and cohesion. Then, calculation of infiltration to estimate pore water pressure regime in the moment of failure were done. Permeability tests revealed that the coefficient of permeability in the location of the landslide was lower than in other part of analyzed terrace. furthermore infiltration results revealed that the analyzed rainfall was intense enough to saturate the soil profile in area of the landslide. Back-analysis showed that the soil from landslide’s area is characterized by relatively low value of effective cohesion (0,6 kPa) and high value of effective angle of internal friction (40,1º).

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