In this study, two types of smart rocks are proposed, characterized, and validated for bridge scour monitoring, including the arbitrary oriented system smart rock and the automatically pointing to south system smart rock. Effect of the smart rocks on the geomagnetic field is numerically studied, and algorithms to localize the position of the smart rocks are developed. Field validation tests are conducted at an open area in Rolla, MO, USA. Results show that the magnetic intensity decreases in cubic function with a distance away from the smart rock. The algorithm can effectively localize the position of smart rocks during validation tests. The effective monitoring range of the two smart rocks is dependent on the flux (or size) of the magnet used to fabricate the smart rocks, the accuracy of the magnetometer, the direction of smart rocks, as well as the intensity and variation of the ambient magnetic field. Compared with arbitrary oriented system smart rock, less measurement points are needed to localize the automatically pointing to south system smart rock.