بررسي قابليت كاربرد معادلات رژيم در طراحي مجاري آبرفتي منطقه كامفيروز استان فارس

Investigation of applicability of regime equations design of alluvial canals of Komfiroz area in Fars province

Design of alluvial canals by using regime equations has been a subject of research during recent decades. The underlying theory dictates that for a canal in regime, water discharge, sediment load, canal geometry and slope, as well as other flow variables should be in equilibrium. For the design of alluvial canals, a number of regime equations have been developed by investigators such as Lacey, E3lench, Simons and Albertson, Parsa and Javan. In the present study, applicability of the above regime equations was investigated. Then based on field data modified equations were presented. Field data included the measurement of flow discharge, flow velocity, geometry of canal cross section and slope of water surface in 29 earthen canals. The sizes of bed and side materials of these canals were also measured. Compassion of different regime equations indicated that the equation by Parsa and Javan provided a better estimation of hydraulic parameters as compared with other equations, because in this equation, flow width and depth were related to slope as well as flow discharge. Since in Parsa and Javan equation water surface slope was an independent variable, their equation can be applied to a wide range of flow conditions. Since all other equations were developed using local data, they can provide good results, If used in similar conditions. Therefore, in Komliroz area their use did not lead to suitable results. For the case of Simons and Albertson equations, they were comparable to Parsa and Javan results. This was due to fact that their equations did not include limitations as imposed by other investigators. Using slope as an independent variable can predict the equilibrium conditions with more accuracy.