This research is funded by the Environment Agency and United Utilities whose support is gratefully acknowledged. Some of the methods employed in this work have been tested on the background of the results obtained in MorphSed (www.morphsed.es), a research project funded by the Spanish Ministry of Economy and Competiveness and the European Regional Development Fund Scheme (FEDER; CGL2012-36394). The second author is funded by a Ramon y Cajal Fellowship (RYC-2010-06264). Authors acknowledge the support from the Economy and Knowledge Department of the Catalan Government through the Consolidated Research Group ‘Fluvial Dynamics Research Group’ (2014 SGR 645). The authors thank Manel Llena from the University of Lleida for his help and contribution to the camera calibration experiments. We are also grateful to the three anonymous reviewers and the editors for their comments that greatly improved the manuscript.Peer reviewedPostprin
