Evaluation of image-based velocity measurements for computing river discharge in real-time
Résumé
Quantifying key hydrological parameters, such as the river discharge, during high flow events frequently faces
technical difficulties and is potentially dangerous to operatives. The application of novel hydrological monitor-
ing techniques may reduce these risks, and offers the potential to rapidly advance our understanding of operating
processes, which may reduce risk to society. We therefore propose a low-cost non-contact alternative method to
determine river discharge in real-time. Our approach is an image-based technique, where video footage is subjected
to optical flow tracking algorithms, enabling the displacement rates of naturally-occurring features on the water
surface to be computed. This is achieved through the application of the Kanade-Lucas-Tomasi (KLT) particle im-
age velocimetry (PIV) approach. We installed our real-time camera system at the Environment Agency’s Austin’s
Bridge Gauging Station on the hydrologically responsive River Dart (SW UK). Our objective was to compare
discharge measurement results obtained with our KLT-PIV method to those from an established and well-proven
flow measurement station. We compared our measurements with 73 ADCP transects at discharges ranging from
3-101 m3 s-1 and the official rating curve of the Environment Agency. We obtained promising results, our KLT-PIV
surface velocity measurements were predominantly within 10% compared to the Environment Agency’s discharge
computation. This indicates that the KLT-PIV technique offers potential for the safe and cost-effective real-time
assessment of river flows, even in potentially damaging high magnitude flood events. Therefore, it offers the oppor-
tunity for greatly improved flow monitoring in countries with established networks, and for the rapid development
of monitoring where networks are less well developed.