Natural Environment Monitoring 2011, No 12, 59-68
GENESIS AND FLOODS COURSE IN THE FLYSCH BYSTRZANKA CATCHMENT IN THE PERIOD 1995–2009
Floods in small streams are the subject of numerous publications, especially in recent years, when marked the increase extreme meteorological and hydrological risk. The size of the floods is related mainly with weather conditions, especially with the precipitation and the other elements e.g. the period prior the floods, the state of the catchment retention, the manner and condition of the vegetation cover, the catchment parameters and in the winter: the water content in snow or depth of the soil freeze. Studies on the genesis and floods course were conducted in the flysch Bystrzanka catchment in the period 1995–2009. The catchment location makes two relief types to interweave. These are the relief of the Carpathian Foothills and of the Beskidy Mts., controlled by geologic structures and tectonics.
The predominate type of the floods in the catchment are normal floods inducted by rainfall. The discharge with the high water level represent mean 7% of the hydrological year, are short (3,2 day) with one discharge wave, usually single. Floods which occur in the winter half year have a longer duration. It is related with the way of water supply to the main stream by the slowly snowmelt from the different and asymmetric part of the catchment. The discharge which are notice in the Bystrzanka stream are typical of the Eastern Macroregion – with the runoff predominance in the winter half year (November–April) (54%). The discharge coefficient show the complex regime, snow-rain. Analyzed period (1995–2009) in terms of the genesis, the number of floods, course, is typical in comparison to the other small stream but well reflects the environment transient from west to east and from Carpathian Foothills to Beskidy Mts.