Slovenia is considered as one of the most water-abundant countries in Europe. Due to its location, most rivers and streams have steep watercourses, which means that there is a rapid formation and concentration of rainfall runoff. During heavy rains, strong surface currents are formed, which on steep terrain form powerful and destructive flows which may endanger property and lives. Through various interventions in the water bodies, we reduce the longitudinal slope of the watercourse as well as ensure better hydraulic conditions, improve safety for people, prevent bank flooding and protect the environment and nature. These interventions can be carried out in the watercourse itself, or in its surrounding riparian areas. Interventions carried out in the watercourse often include construction of weirs. Rapids and chutes also occur in the environment as a result of the natural dynamics of hydraulic and erosion conditions. Their presence in the aquatic environment is thus something quite common.
In the master's thesis, we focused on weirs, especially the impact of their removal on the hydraulic conditions in the watercourse. In the first part, we presented the basic characteristics of weirs, their properties, what factors we need to consider when placing them in an environment and potential limitations. Equations for the design of weirs in the watercourse are also presented. In the second part, we analysed different scenarios of riverbed transformation after the removal of an existing weir (a chute) in the Kamniška Bistrica river. We analysed how the hydraulic conditions in the riverbed change, with an emphasis on the water levels, velocities and shear stresses along the studied section.
It should be noted that the removal of a weir in a watercourse can often lead to complex changes in the in-stream channel hydraulic conditions. Each watercourse is unique, so it is necessary to study the method of riverbed transformation on a case-by-case basis. In the practical example of the removal of the chute in Kamniška Bistrica, we assumed five different scenarios for the transformation of the riverbed. Overall, the results were similar, but there were also significant differences between the resulting hydraulic condition. Therefore, it is necessary to understand the hydraulic characteristics and hydromorphology of the aquatic environment to determine the potential worst-case scenario of watercourse channel hydromorphology transformation.
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