The Hydraulic Calculation Of Open Channel And The Flood Control Evaluation Using Uneven Spot Roughness Method

With the continuous development of urban river construction, various hydraulicstructures and plant communities appear in these rivers in the demands of ecology andhuman activities. Although these kinds of river is nature-friendly and man-convenient,it cannot be ignored the impact on water elements from these objects because theimpact of blocking water is obvious. It particularly enhances the requirements offlood control standard in urban areas. So making a systemic flood control evaluationhas a strong correlation with human life and property securityThis article selects the Manning resistance coefficient to describe thewater-blocking effect of river objects, discussing the resistance of water imposed bythese objects by selecting the piers in the urban rivers as the research objects. Itgeneralizes piers communities into equivalent river resistance coefficient theoretically,thereby putting the complex piers communities into Manning roughness expression byusing equivalent Manning roughness coefficient with the aim of simplifying theprocess of calculation on rivers that contain bridge piers. This equivalent expressiononly appears around the piers while the roughness of the other area is the originalvalue, so it has a limited applicable range. In this paper, this equivalent roughnessvalue is named "Spot Roughness", and numerical simulation and physical model areused to test and verify this simplified method.In this paper, numerical simulation based on the Liuting section of Baisha riverin Qingdao analyses of the generalization of river bridges, and Spot Roughness isused in two-dimensional numerical simulation of the channel. Comparing thesimulation result with that of the normal river simulation which involves bridges, thefeasibility of this method is observed, and the simplicity of this method is proved.In this paper, longitudinal bridges crossed the river are adopted in physicalsimulation. Use the hydraulic parameters got from the experiment to deduce theroughness value, and compare these values with the equivalent roughness from the theoretical method. It shows that the two results are very close to each other so thatthe equivalent roughness method is feasible, proving the applicability of thisroughness value assignment method again.