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Definition of ecological functionality indicators for Mediterranean braiding rivers

Programme de recherche « Définition d’indicateurs de fonctionnalité écologique pour les rivières à tresses de Méditerranée » porté par Margot Chapuis (Maître de conférences, Université Côte d’Azur, UMR 7300 ESPACE)

The European Water Framework Directive (WFD) of the European Union aims at improving the quality of European water bodies and resources by 2027. Concerning rivers, a first step is to make a diagnosis of the ecological and chemical “health status” of the rivers, which is then used as a base to restore, if necessary, the degraded water bodies.

However, establishing rigorous criteria to estimate whether a river is in “good health” is challenging. It is especially difficult in the case of braided rivers, which are common in South-East France. Braided rivers are characterized by strong hydrodynamics that induce rapid space-time changes in their morphological pattern and biological content. On the one hand, their rapid changes make them difficult to monitor, while, on the other hand, they generally quickly recover from a disturbance, which may hide their actual “health level”. Therefore, robust diagnosis tools are needed to properly assess the actual ecological status of braided metastable river systems. The MedRiver project aims at developing such tools, specifically targeting braided rivers in a Mediterranean context. Some of these tools already exist, but most are mono-discipline, addressing either the biological, the ecological, or the geomorphological context of the river. We have thus developed an original set of multi-parameter “good status” indicators for braided rivers. One of those new indicators links geomorphic and vegetation pattern evolution. We use it to examine, in historical and remote sensing data, the temporal and spatial evolution of four braided river systems in Southern France (Var, Durance, Bléone, and Drac) and one in Italy (Mareta, Bolzano region) following their restoration which was conducted from 2008 to 2019. Meanwhile, we have also shown that some of the existing indicators (such as BRI* and W*) originally developed on pristine rivers, also apply successfully to channelized braided rivers; they well document river systems evolution subsequent to their restoration. Finally, we have developed another set of indicators that combine geomorphic and ecological parameters (such as aquatic macro invertebrate content, and partly as terrestrial invertebrate content). Those should allow us to examine the spatial and temporal variability of braided river habitats and to quantify the successfulness of river restoration operations (Devreux et al., in prep.).

The new diagnosis tools will ultimately be provided to the river managers to help them plan and prioritize the restoration operations in the Mediterranean braided rivers.

Productions

• Colloque :
• Publications

Articles
Devreux et al. (in prep). Changes in the invertebrates community after restoration in an Alpine braided river. Science of the Total Environment.

Lise Devreux, Margot Chapuis, Barbara Belletti (2022). Hydromorphological analysis on restored Alpine braided rivers. Geomorphology, 415, pp.108404. ⟨10.1016/j.geomorph.2022.108404⟩. ⟨hal-03794714⟩

Lise Devreux, Margot Chapuis, Barbara Belletti (2021). EVOLUTION DU TRESSAGE SUITE A DES OPERATIONS DE RESTAURATION SUR DES RIVIERES EN TRESSES. Transport sédimentaire : rivières & barrages réservoirs, Mar 2021, Saclay, France. ⟨hal-02967555⟩ (accepté)

Actes de colloque
Lise Devreux, Margot Chapuis, Barbara Belletti (2022). Évolution du tressage suite à des opérations de restauration sur des rivières en tresses. TSMR : Transport sédimentaire : rivières & barrages réservoirs, Mar 2022, Saclay, France. ⟨hal-03794793⟩

Communications
Lise Devreux, Margot Chapuis, Barbara Belletti (2021). Sampling protocol to study benthic invertebrate community in a restored braided river. Symposium for European Freshwater Sciences, Jul 2021, Dublin (virtual), Ireland. ⟨hal-03344244⟩

Poster
Lise Devreux, Margot Chapuis, Barbara Belletti. Développement d’une nouvelle méthodologie de prélèvements des invertébrés benthiques sur une rivière en tresses restaurée. I.S. Rivers, Jul 2022, Lyon, France. ⟨hal-03794756⟩

• Partage de données et de méthodologie
  Zenodo : package braidHymo
  Lise Devreux, Lise Vaudor, Sandrine Lallias-Tacon, Barbara Belletti, Mathieu Cassel, Frédéric Liébault, & Margot Chapuis. (2021). braidHymo: Morphometric indices for braided rivers. (v1.0.0). Zenodo. https://doi.org/10.5281/zenodo.5796184
  Le package braidHymo permet de calculer deux indices morphométriques qui peuvent être appliqués aux rivières en tresses : le Bed Relief Index (Indice du relief du lit ou BRI*) et le W* (largeur de la bande active normalisé). Deux tableaux de données sont inclus dans le package pour aider et visualiser le calcul des indices.

• Site internet du projet
  (Extrait de Livret academie3, p. 42-43) :