The Impact of Extreme Hydro-Meteorological Events on the Transformation of Mountain River Channels (polish Flysch Carpathians)

Extreme hydro-meteorological event disrupt the balance of natural systems, such as river channels. This paper focuses on changes in mountain valleys associated with a hydro-meteorological event that occurred in the Polish Carpathian Mountain in May and June of 2010. On three rivers (Ropa river, Bielanka and Bystrzanka streams) the geomorphological effects were mapped. Continuous and high intensity rainfalls, the sum total of which exceeded 432 mm in May and June, contributed to the significant increase in water levels and changes in the channel morphology. The dominating process in the upper courses of the streams was erosion while in the middle and lower courses it was erosion with deposition, which led to the building of extensive accumulation forms with woody debris. The calculated high values of the unit stream power indicate that Carpathian streams have tendencies to transform the bedrock channel, which is evidenced by the sizes of the transported boulders. The research confirm the hypothesis that grouping of several events in a short period of time is the most important factor shaping river channels in mountain regions.