Quantification of the morphodynamics and ecological functionality of a Mediterranean river

Description

The Var River (South-Eastern France) is currently undergoing an ambitious restoration project that aims at restoring its 'natural' active braiding pattern ('Mediterranean facies') on the channelized downstream reach of the river. As part of the ongoing feedback evaluation of such project, this study aims at: (1) quantifying the morphological evolution of the bed that is recovering from sediment discontinuity; (2) identifying and/or developing hydromorphological and ecological indicators which vouch for improvement of the Mediterranean river system, from a hydrosedimentary and ecological point of view. We used LiDAR and orthophoto datasets and performed analyses described in the literature for unchannelized braiding rivers [1, 2]. Active width (Wrestored = 242 ± 19 m vs. values ranging from 103 ± 53 to 163 ± 53 m for 'unrestored' reaches) and normalized bed relief index values (BRI*restored = 0,003 ± 0,001 vs. 0,003 ± 0,003 to 0,007 ± 0,004 for 'unrestored' reaches) indicate a combination of low rugosity and wide active width. Thus the 'restored' reach shows a different set of indices compared to adjacent 'unrestored' reaches, which suggests that these tools are promising in discriminating 'restored' vs. 'unrestored' reaches. Adapting existing analysis process from 'natural' to 'channelized' braiding rivers enabled us to widen the potential application of the tools developed by Lallias-Tacon [2] to modified braiding river systems.

Abstract

International audience

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