Time-lapse photography to track fluvial sandbars.

What is it about?

A simple methodology to track the displacements of a sandbar from a fixed video camera, extracting its morphological features and deriving the associated fluvial morphology is presented, using a small reach of the Po River in Italy as a case study. A camera fixed on a bridge pier acquired images every twelve hours while hourly water levels are derived from a radar hydrometer located upstream of the study area. The quantification of the fluvial bathymetry is achieved by mapping multiple edge-of-water lines of a sandbar before and after high flow conditions in December 2017. Both from video information and 2-D numerical simulations, it is evident that flooding waves can easily remove sediments that accumulated on bars during low flow conditions in this area, redistributing them across the river channel.

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Why is it important?

This video-based methodology—which confirms to be economically attractive if compared to more traditional monitoring systems—proves to be a valuable system to monitor long-term fluvial processes providing detailed indications on how to better plan river management activities.