A hybrid model that combines finite element and genetic algorithms is developed to estimate the scour depth around bridge piers by using the natural frequency of the bridge structure. Scouring around bridge piers is an important safety issue of bridge management since it could lead to bridge slanting and collapsing. However, the mechanism of water flow around the pier structure is very complicated, which makes it is very difficult to develop a generic model to determine the scour depth and the bridge safety. Many researchers have tried to estimate the scour depths around bridge piers by simulating the bridge model with various factors, such as the depth of water, average velocity of flow, and diameter of sand. However most of models can only be applied to certain types of bridges under some predefined conditions. In this tusy, the finite element method is used to simulate various conditions by mesh such as pile foundations type, soil strength, and scour depth. Since simulations generate a huge amount of data, which makes it hard to analyze and find the relation between the scour depth and the natural frequency, genetic algorithms are used to find the fitted generic formula that defines the relationship between the scour depth and the natural frequency. In this paper, soil strength compare with natural frequency within different bridge scour depth is discussed.