In the present study is characterized the synoptic situation and conditions, which led to a debris flow event in the Manastirska River valley on August 22, 2022. The main reason for the occurrence of this hazardous events is predetermined by one of the right tributaries of the Manastirska River. For the purpose of the study, several morphometric parameters of the tributary were calculated and analyzed such as area and shape of the basin, slopes, aspect, drainage network length, drainage density, etc. The type and the transportation of the sediments were determined by measurements, grain-size and clast-shape analysis. The impact of weather conditions on debris flow occurrence were determined by the analysis of the synoptic conditions on the days before the event.

The block fields and block streams are widespread in the Pirin Mountains. They are significant in size and are distributed on both relatively flat and sloping surfaces. Their origin is associated with frost weathering, which can subsequently be supplemented by other processes related to the destruction of the material – chemical weathering, fluvial, cryogenic processes, etc. The main aim of the study is to analyze the block field and block stream deposits which will give us a better understanding of their origin and evolution.