Estimation of Basic Geometric and Hydraulic Characteristics of Natural Torrent Beds

Abstract

Many mountainous regions and their watersheds lack the mathematical description of their hydraulic geometry such as the High Tatras region in Slovakia. Therefore, the aim of the paper is to determine the geometric and hydraulic characteristics of natural torrent beds and to propose a regional equations of mountain watersheds for the High Tatras region. In the paper is also proposed a new equation to determine the relationships between the watershed area and the geometric characteristics of flow profiles. Derived regional equations can help in nature-friendly and ecological shaping and dimensioning of channel cross sections in torrent control designing. The research was conducted in 26 natural torrents and their watersheds on the reference sections and profiles under the sediment source zones. Two different regression equations to determine the regional relationships (hitherto used without asymptote and newly proposed with asymptote) were compared. The analyses showed a strong correlation relationship between watershed area Aw (km2) and bankfull geometric characteristics of natural cross-sections: width of the channel inside the banks Bbf (m), mean channel depth Hbf (m), channel cross-section area Abf (m2) and hydraulic characteristic – bankfull discharge Qbf (m3.s-1). These relations were tested by t-test and Shapiro-Wilk test. The determination coefficient (R12) for the relationships without asymptote ranged between R12 = 0.919 and R12 = 0.972; p1 – values from Shapiro-Wilk test ranged between p1 = 0.0359 and p1 = 0.8027. The determination coefficient (R22) for the relationships with asymptote ranged between R22 = 0.952 and R22 = 0.974; p2 – values from Shapiro-Wilk test ranged between p2 = 0.0221 and p2 = 0.8617. At the same time, we tested and confirned the hypothesis that the correlation coefficients R1 from equation without the asymptote are only randomly different from the correlation coefficients R2 from equation with the asymptote and the difference between these coefficients is also random. Derived regional equations make it possible to the gradual creation of hydrologic landscape regions in the SR. They can be also used as a valuable input to the ecological cross sections designing in torrent control and revitalization for the regions with a similar natural conditions.