Local scour is a major risk threatening the stability and sustainability of bridges across rivers and in coastal areas. The main purpose of this paper is to propose a monitoring technique based on the dynamic response of rods embedded in the riverbed. First, extensive laboratory tests are conducted to investigate the effect of scour on the vibratory response of different rods in sand and in saturated clay soil. Secondly, a numerical finite element model is developed and validated with these laboratory tests. This model is then used to assess the effect of the added mass of water on the sensor. Finally, based on the numerical and experimental results, a simplified analytical cantilever model is proposed to correlate the dynamic response of the rods to the current scour depth.