Antiflow screens are often used to improve seepage conditions through earth hydrotechnique constructions. Mathematical researches of seepage allowed, during project works, to estimate these construction components efficiency and establish useful variant for protecting safety of new projected and modernized antiflood embankment Odra river at Kozanów. Increase seepage coefficient from 0 to 0.1 md-1 cause flow increase by 15–75% for homogeneous and by 60–200% for anhomogeneous cross-section. Otherwise, increase thickness of earth screen from 0,25 to 1,00 m cause flow decrease by 10-30% for homogeneous and by 30–100% for anhomogeneous cross-section. ...
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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In the article an influence of measurement inaccuracy of longitudinal and transverse dispersivity coefficients on solutions of dispersion equation, which is a basis of mathematical model of pollutant movement in groundwater, was inves-tigated. An analytical solutions of dispersion equation for temporary or constant point source of pollution were used. Inaccuracy of dispersivity coefficients was de-scribed by normal distribution. Multivariable computations for various values of dispersivity coefficients enable to notice that time-space distribution of pollutant concentration depends on parameters of dispersion equation. Maximum coefficients of variation of computed concentrations are situated near boundary of con-taminated region. These are regions of maximum risk of incorrect result of compu-tations. Area average coefficient of variation for constant and temporary source of pollution is non increasing time function. Its denote stability of mathematical model for pollutant movements in groundwater. ...
