Garonne tidal bore research. Researchers preparing topographic and hydrodynamic sensors to study the Garonne tidal bore. A tidal bore occurs when a large tidal range causes water to surge into a funnel-shaped bay, river, or estuary. This is the Gironde estuary in south-western France, at the meeting of the Dordogne and Garonne rivers. This research is being carried out by a CNRS (French National Centre for Scientific Research) EPOC (Environnements et Paleoenvironnements Oceaniques) research group from the University of Bordeaux 1. Photographed near Podensac, France, on 6 September 2010.