The research is conducted to model the stability of river banks subjected to tide variation, with particular reference to the Mekong delta. Dupuit assumption is supposed to find the variation of water level in the soil using a numerical solution by an explicit finite difference method which results are compared to field measurements. Under periodic tide variation, a stable ground water level is obtained far from the river bank and higher than the mean river water level. A limit equilibrium analysis (slice method) is developed to find the safety factor of the riverbank. Validation of the results is conducted by comparing to finite element calculations. The safety factors vary with the change of water level in the river. The critical instant (minimum safety factor) occurs during the low tide period. The soil permeability has an influence both on the critical moment and on the corresponding safety factor. Furthermore, the soil cohesion has an effect on the shape of the failure surface.