Impact of Downpours on Fluvial Processes in the Polish Carpathians as Exemplified by the Bystrzanka Stream
This paper present the results of the geomorphological mapping of transformations in the Bystrzanka channel after the rainfall in May and June 2010. Mapping data from June 2010 were compared to observations from April 2010. Total rainfall in the 20 day period from 15 May to 3 June was 320.4 mm, which constituted the highest two decade value in the last 40 years. Research of concentration of suspended sediments showed that sediments concentration in the main tributary (Gerucha) during the flood on June was up to 4.5 times higher than the concentration in the Bystrzanka. High discharge (57.7 m s) have caused significant transformations of the Bystrzanka channel (main stream 7,1 km, area 13 km) Numerous cut banks occurred at an irregular fashion along the whole length of the stream. Cut banks of the channel most often reached the height of 2 m. Point bars and central bars of varied size and shape, depending on channel morphology, were observed along the whole length of the study channel and consisted mainly of sand, gravel, and boulders both abraded (in varying degrees) and non abraded. Also observed was the activation of rotational landslides at the stream banks, the fronts of which almost entirely blocked the bottom of the stream. High discharge during the flood caused damage to the road, resulting in the riverbank receding by about 10 m.