Precipitation is one of the main factors causing surface, linear and landslide erosion. Their influence on erosion processes is determined by such parameters as: precipitation frequency, amount, duration and intensity. These features affect the rate of infiltration and the intensity of surface runoff, and thus the occurrence, course and effectiveness of erosion processes [2, 3, 4]. The aim of research was to analyse the 40-years of rainfall measurements data from the Lubuskie Voivodeship and inspect whether occurring of heavy rains are random events or maybe indicate some long period trends. To analysis was used non-parametrical Mann-Kendall test and correlation test. What is more the authors’ prepared a path of selecting the optimal dewatering system, where would be taken into consideration ground stability and changes in the rainfall trends. For this purpose, the paper contain short overview existing dewatering systems which are used to reducing risk of landslides.