Acta Scientiarum Polonorum. Formatio Circumiectus (Dec 2017)
Boulder cluster influence on hydraulic microhabitats distribution under varied instream flow regime
Abstract
The study is related to determine the influence on local hydraulic conditions of a group of boulders carried out in 2016 in the context of a restoration project in the Wisłoka river channel. After the boulders deposition in 2013, the study aims to determine whether there is a local impact of the cluster on the microhabitats distribution. The studied hydraulic features were: velocity, velocity pulsation, discharge, water depth and topographical measurements from three field sessions at three different discharges (31.2, 19.3 and 10.4 m3 • s–1). A study of the velocity profiles as well as pictures and videos allowed to determine the microhabitats distribution. Calculation method presented by Byczkowski were used to get mean velocity values. The boulders create different kinds of velocity profiles: „logarithmic”, „uniform”, „reverse logarithmic” and even with „negative velocities”. The cluster influences on the creation of different microhabitats. Distribution of them depends on discharge value. „Fast run”, „turbulence zone”, and „recirculate zone” have been observed around boulders at higher discharge. This influence is not so strong for the lower discharges, but the creation of several microhabitats can still be observed: „shallow water”, „turbulent”, „ripples”.
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