<p>Bridge failure caused by flood-induced scour around piers remains the primary threat to traffic disruption and life losses. Real-time monitoring of scour variations is crucial to avoid bridge failure. The scour monitoring system is developed and implemented in the field, consisting of vibration-based MEMS (micro-electromechanical systems) arrayed sensors for water level and flow velocity measurement. The scour monitoring system records scour and deposition depth changing over time at the bridge pier in flood events. A numerical simulation module combining one-dimensional and two-dimensional mobile-bed hydrodynamic models is established to calculate scour and deposition depths based on field hydrological conditions. The field-measured data from the real-time scour monitoring system are employed for model validation. Due to the complexity of hydraulic sediment transport mechanisms around the pier, several local scour formulas have been evaluated to verify their applicability. Using field-measured scour depth data, a suitable local scour formula for the Mingchu Bridge in the Cho-Shui River is developed. The real-time scour monitoring system coping with the numerical simulation module developed in this study can provide accurate information on scour and deposition processes at the bridge pier, which is helpful for decision-makers to assess the risk of bridge damage and the timing of bridge closure. Finally, the proposed bridge safety curve referring to four bridge warning stages based on the pier foundation characteristics, as a determinate relationship between scoured bed level and discharge, has been established to assist bridge managers in making rational decisions on bridge closures during floods.</p>