Mesure des débits par photogrammétrie adaptée aux rivières torrentielles

Reliable discharge measurements are indispensable for an effective management of natural water resources and floods. To address limitations of classical measurement methods in the mobile riverbeds of the Reunion island, the Office de l'eau Reunion, the University of Western Brittany and the University of La Reunion developed a photogrammetric discharge measurement system. The PIV-based (Particle Image Velocimetry) system measures the flow velocity at the surface from video streams, the riverbed is reconstructed with multi-view photogrammetry and the wetted surface is detected automatically. The image processing chain has been implemented in MATLAB to (i) process video-streams in near real-time enabling and (ii) aggregate multiple images to discharge time-series with a 30 min measurement interval. Comparisons against classical current meter profiling show a mean absolute percentage error of 9.0% after the statistical calibration of the system. This technology can be deployed autonomously or connected to the power-grid and opens new perspectives for monitoring of discharge in complex environments and during extreme hydrological events.