In the paper some the most important, characteristic parameters for vegetation density description are presented. The density of vegetation in the river beds is one of the most important parameters that has impact on the flow conditions in the river. The mathematical formulae for flow resistance and water level calculations contain the density of vegetation zone as a parameter. This parameter can be described by various methods. The compact specification of plants parameters is given in the paper. ...
This paper aims to improve the reliability of the determination of flow resistance and hydraulic effects of vegetation. For this reason, laboratory flume studies with living vegetation were employed. The most notable finding was that, when compared to leafless conditions, the presence of leaves increased the friction factor up. This was strongly dependent on the flow velocity. The work shows the results of studies conducted in water laboratory the Department of Hydraulic En-gineering the Poznan University of Life Sciences and Institute of Environmental Engineering Wrocław University of Environmental and Life Sciences. Subject of research done on hydraulic was to assess the direct natural vegetation under the influence of water flow. To analyze this phenomenon adopted the model of water resistance movement on vegetation. To designate determined resistance forces in-cluding vegetation structure and flow by above it.
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Vegetation growing in the River Bed is strongly influencing flowing condi-tion. Effective flow section is reduced, velocity field is disturbed and flow resistance is increased. Its consequence is change of water level and depth in comparison with flow in river bed without vegetation.Equations of momentum conservation in river bed with trees based on a concept of whirly viscosity proposed by Rowiński and Kubrak [2002] are one of mathematical description of vegetation hydraulic influence. Above equations were solved using implicit and explicit differential scheme to determine flow velocities distribution in vertical profile. Accuracy of proposed algorithms was tested by comparing numerical solutions with detailed analytical solution obtaining very good conformity. Velocity distribution calculated on the base of the model was used to determine volume of the flow. To evaluate possibilities of using developed model for calculation concern-ing small rivers with vegetation, some filed investigation on one section of Ślęganina river were carried out. Despite of geodetic measurements, some profiles of local flow velocities for vegetated and free of plants sections were made. Field measurements results were used for verification of mathematical model based on equations of momentum conservation.
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