University of TehranIranian Journal of Soil and Water Research2008-479X51220200420Longitude Profile Analysis of Water Table in Rockfill Materials Using Gradually Varied Flow Theory with Consideration of Drag ForceLongitude Profile Analysis of Water Table in Rockfill Materials Using Gradually Varied Flow Theory with Consideration of Drag Force4034157371910.22059/ijswr.2019.287292.668295FAMohammadGudarziM.Sc. Student in Water and Hydraulic Structures, Department of Civil Engineering, Faculty of Engineering, Zanjan University, Zanjan, IranJalalBazarganAssociate Professor, Department of Civil Engineering, Faculty of Engineering, Zanjan University, Zanjan, IranSeyyed MohammadShoaeiAssistant Professor, Department of Civil Engineering, Faculty of Engineering, Zanjan University, Zanjan, IranJournal Article20190825The flow analysis in rockfill materials is often fulfilled by solving differential equations that combine non-linear equation [i=mv<sup>n</sup>] and continuity equation. This differential equation has first been developed by Parkin. It's solution by finite difference method is massive and time consuming, proportion to boundary conditions at this particular case. These calculations would end up with more significant problems where the water table profile is not specified inside the rockfill material. For flow analysis in rockfill material, another method can be used which is based on the gradually varied flow theory. This method is very simple and less massive. Literature review shows a significant error in parts of flow in which the curvature of the streamlines is high, if drag force is not considered in the gradually varied flow theory. In the current study for the first time, using experimental data of different rockfill materials, the effect of drag force on water profile calculation accuracy was investigated considering gradually varied flow theory. The results show by considering drag force, the calculation accuracy of water profile at permanent flow, especially in high flow curve, would significantly increase and a promising results could be obtained.The flow analysis in rockfill materials is often fulfilled by solving differential equations that combine non-linear equation [i=mv<sup>n</sup>] and continuity equation. This differential equation has first been developed by Parkin. It's solution by finite difference method is massive and time consuming, proportion to boundary conditions at this particular case. These calculations would end up with more significant problems where the water table profile is not specified inside the rockfill material. For flow analysis in rockfill material, another method can be used which is based on the gradually varied flow theory. This method is very simple and less massive. Literature review shows a significant error in parts of flow in which the curvature of the streamlines is high, if drag force is not considered in the gradually varied flow theory. In the current study for the first time, using experimental data of different rockfill materials, the effect of drag force on water profile calculation accuracy was investigated considering gradually varied flow theory. The results show by considering drag force, the calculation accuracy of water profile at permanent flow, especially in high flow curve, would significantly increase and a promising results could be obtained.https://ijswr.ut.ac.ir/article_73719_9502f0cb37929245294f5810d14500f5.pdf