Morphogenesis of Torrent Beds in the Watersheds with a Different Geological Bedrock and Geomorphological Rock Value

The paper deals with the morphogenesis of natural torrent beds in two watersheds with different geological backgrounds and a different geomorphological rock value: Hučava (geomorphological unit of Poľana with geological bedrock: neovulcanites – pyroxene and hornblende-pyroxene andesites, andesite porphyry, rhyolites, rhyodacites, rhyolite tuffs, diorite porphyry) and Mútňanka (geomorphological units of Podbeskydská brázda and Oravské Beskydy with geological bedrock: flysh – claystones, sandstones, shales-thin bedded flysh, microconglomerates). The bankfull geometric characteristics of a natural reference cross-sections of these torrents: the width of the channel inside the banks W_bkf (m), mean channel depth D_bkf (m), channel cross-section area A_bkf (m²) and the hydraulic characteristic, namely bankfull discharge Q_bkf (m³.s^-1) in relation to the watershed area A_w (km²), were analyzed and compared. The analyses showed a strong correlation between the watershed area A_w (km²) and the bankfull geometric characteristics of natural cross-sections: W_bkf (m), D_bkf (m), A_bkf (m²) and the hydraulic characteristic Q_bkf (m³.s^-1). In the analyzed relationships, the coefficient of determination (R²) ranged from R² = 0.905 to R² = 0.962 in the Hučava torrent and between R² = 0.912 to R² = 0.958 for the torrent of Mútňanka. Using statistical testing, the significance of the differences between the absolute and as well as regression coeficients in the hydraulic geometry equations for these torrents and their watersheds of different geological bedrock were confirmed.