Development and Application of an Automated River-Estuary Discharge Imaging System

An automated river-estuary discharge imaging system (AREDIS) is developed to measure the velocity of a wide tidal estuary. The system contains near- and far-field cameras that capture the entire 370-m-wide channel from an oblique angle with high image resolution. A new rotational scheme is developed to calibrate the cameras. Wakes generated by flow past bridge piers are found to be natural tracers for large-scale particle image velocimetry (LSPIV) to reliably and accurately measure the surface velocity, confirmed by buoy tracking velocimetry (BTV). The success of AREDIS is demonstrated in three field measurements on the Danshui River, the largest estuary in Taiwan. First, AREDIS is used to measure discharge over the entire tidal cycle under normal flow, and a 10% difference is found between discharges measured with AREDIS and a boat-mounted acoustic Doppler profiler. Second, AREDIS is employed to measure discharge under a typhoon event, resulting in discharges 45% greater than those at normal flow. Finally, AREDIS successfully measures discharge at night by tracking the motion of lighted buoys, a first for image-based measurements. Overall, AREDIS is demonstrated to effectively measure flow and discharge for wide tidal estuaries.