Monitoring and Simulation of Bridge Pier Scour and Deposition Processes in Flood Events

Abstract 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 micro-electro-mechanical systems (MEMS) arrayed sensors with the water level and flow velocity measuring instruments. The scour monitoring system records scour and deposition depth varying with time at the bridge piers during 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 obtained from the real-time scour monitoring system are employed for model validation. According to the complexity of hydraulic sediment transport mechanisms around the pier, several local scour formulas are evaluated to verify their applicability. Using field-measured scour 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, 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 typhoon seasons.