A Method for Calculating Unsteady Seepage at Riverbank

The paper presents a method to calculate the unstable seepage at riverbank. The Laplace’s equation in saturated zone is solved by the finite element method. Time derivative terms are discretized using implicit finite difference schema. The method considers three special factors of seepage including the change in time of water level of river; the variation in time of the phreatic line; and the variation of discharge face on river slopes. In response to the changes in time of the phreatic line, the computation mesh is modified at each step. The computation grid modification is performed using transformation. Although the implicit finite difference schema is used for discretization of time derivative terms, it is not required to know old pressure head at the nodes in new location. The method has been verified through a number of problems performed by other authors, including steady and unsteady seepage through rectangular earth dams, seepage flows through dams with a periodic boundary condition. The calculation results show that the method has a good accuracy.