## 1 Introduction  
Slope stability, especially among urban areas, is a subject of extensive engineering-geology research [1, 2]. The scope of these studies includes improvement of geological structures' identification, especially glacitectonic ones, as well as optimising methods of forecasting slope stability conditions. The first aspect uses shallow geophysics, which allows more precise identification and mapping of the course of structural disturbances. The second aspect of the analysis concerns the optimisation of computational methods that are applied in forecasting the equilibrium state of the slopes. Such an approach allows the correlation of the results of the identification of shallowly located glacitectonic structures obtained with the use of different methods. It provides a possibility to apply the data acquired with the electrical resistivity imaging (ERI) method to classical slope stability model analyses and to the finite element method (FEM). Combined, the analysed issues can be proposed as a pattern of conducting slope stability research, especially in the case of the wide availability of various research and computational methods, that do not necessarily fit all conditions. The electrical resistivity method can be helpful in determining a model of spatial variability of strata and slope stability. This method is marked by high prospection efficiency and is commonly used to characterise geological structures, e.g., course and depth of geological boundaries, including the position of clays. Vertical electrical sounding [3; 4; 5] and electrical resistivity imaging (ERI) are commonly applied techniques [6; 7; 8] to determine the position of the roof of Neogene clays in Poland. The ERI method, also known as the electrical resistivity tomography (ERT) or continuous vertical electrical sounding (CVES) method, is often used in the mapping of landslides and slope stability [9; 10; 11; 12; 13]. The theoretical basis of the electrical resistivity imaging method, as well as the history of its development and application, was described by [14; 15]. In these studies, the results of an ERI survey were applied to determine the position of the roof of the Neogene clays. The results of the quantitative assessment of the equilibrium state conditions are the subject of numerous analyses [16; 17; 18] and were developed in this work according to the conclusions of [19; 20], among others. An important influence on the methodology development of stability analyses has the effect of studies of landslides at different scales and conditions (e.g., [16; 17; 18; 19; 20; 21; 22; 23; 24]). Models introduced in the analysed case study take into consideration different factors the spatial variability of the geological structure and periodic changes in soil strength properties caused by changes in moisture content and consistency on potential structural slip surfaces. Those changes can be caused by the seepage of rainwater, especially during increasingly occurring events of heavy rains and sewage system failures. The effects of such situations were analysed using multivariant, computer-aided modelling. A number of classical methods of slope stability prediction, based on various assumptions, are in use, although those methods typically do not take geological conditions into account while determining the location of potential slip zones. Another group of analyses uses the modelling of the slope stability conditions based on the finite element method. The comparative approach to the slope stability issue is significant in terms of recognition of optimal slope safety conditions, but also in terms of the evaluation of various prognostic methods. These issues are addressed by the study of the assumptions of both the LEM and the determination of optimal slope slip surfaces using FEM. The obtained results indicate the necessity to further develop an outcome comparison from these two groups of calculation methods [19; 25].