Undercutting is a phenomenon when the soil support underneath a superstructure is eroded by water flow. To simulate this phenomenon a water tank is filled with sand an L bar is placed such that both are at the same level. A model bridge with spring balances simulating its piers is placed such that 3 legs are on the L-shaped wooden bar and the last one is on sand. Two holes are made in the acrylic tank such a way that the sand under the 4th leg is eroded due to the water flow.