© 2015 Elsevier B.V. Numerical simulations are performed to investigate the flow evolution of a depression ISW propagating over a submerged ridge. A finite volume based Cartesian grid method is adopted to solve the Reynolds averaged Navier-Stokes equations using a k-ε model for the turbulent closure. Results reveal a significant transient clockwise vortex and an internal hydraulic jump emerging on the front slope of the obstacle, during the wave-obstacle interaction. This interaction generates an asymmetrical interface and pycnocline thickness on both sides of the obstacle. During this process, the amplitude and velocity of the leading waveform increase transiently, but both quickly decrease once the wave passes the obstacle. As the ridge slope decreases, the wave-ridge interaction weakens, as well as the strength of vorticity and turbulent kinetic energy. In addition, the wave may affect the nutrient transport on the front slope to a maximum depth about 50% height of the obstacle or about 1.78 times of the incident wave amplitude when a large ISW breaks on the slope.