There are many causes leading to riverbank instability and erosion, such as excessive sand exploitation, ship waves, water flow, tidal level, floods, soft ground, human construction activities, etc. In Ho Chi Minh City, where the river system is quite developed and is greatly affected by high tide flooding, the riverbank geology is also strongly affected by tidal fluctuations. The study thus focuses on analyzing the influence of periodic tidal variations on the stability of riverbank slopes. PLAXIS 2D is applied to model riverbank cross- sections with different slopes, from 16° to 55°, under the influence of tidal levels which change over time to assess their influence on displacement, hydraulic gradient and stability coefficient. Consequently, warnings are given about slopes with high risk of erosion. These slopes are compared with observed erosion slopes to check the reliability of modeling. The findings contribute to improving erosion prediction methods by demonstrating how repeated tidal fluctuations can induce progressive weakening of the riverbank structure. These insights have practical implications for the design of riverbank protection systems in estuarine and coastal river environments where tidal actions are prominent.