Tuesday 1st of july – from 14:00 to 19:00
Session B1 : River restoration: strategies, design and participation
Sediment transport of a local sediment supply for spawning habitat restoration: a laboratory/field/numerical coupled study
GRATTEPANCHE Florent, GOMIT Guillaume, CALLUAUD Damien, MERCIER Oliver, COURRET Dominique, SAGNES Pierre
France
Short abstract : This project, supported by le pôle de R&D en écohydraulique OFB-IMFT-Pprime et la région Nouvelle Aquitaine, aims to gain a better understanding of the remobilization of a local input of sediment as part of the restoration of spawning grounds for large salmonids, under unsteady flow conditions, particularly during floods. A methodology combining laboratory studies, field measurements and numerical simulations is used to study a specific site on the Marrone River (Corrèze). This site, located on the short-circuited section downstream of the Hautefage dam, is subject to highly variable hydrographs during dam overflows. These hydrographs are modeled in a laboratory flume using a scaling technique that takes into account sediment properties and hydrodynamic criteria based on Froude and Shields numbers. The data obtained in the laboratory, in addition to providing fundamental knowledge of sediment transport under unsteady conditions, enable transport simulations to be validated without the same conditions. These simulations are then extended to the study site and coupled with field measurements to propose a complete methodology for assessing sediment transport processes and their impact on habitat restoration in a specific case.
Assessing fluvial and riparian vegetation dynamics as indicators of sustainable river management: A bio-geomorphological analysis of the Rio Mareta restoration project (2010-Present)
ROZZONI Alessio, PITTAU Sharon, GEMS Bernhard, SCORPIO Vittoria, ANDREOLI Andrea
Italy
Short abstract : This paper examines the bio-geomorphological impacts and effectiveness of the Mareit river restoration project in the Italian Alps, launched in 2008 to address severe anthropogenic impacts like gravel mining and channel incision. The project aimed to improve ecological resilience through channel widening, reintroducing a braided pattern, and enriching habitats for riparian species. Photogrammetry, Structure-from-Motion (SfM), and geomorphological indices such as MQI and GUSI were employed to evaluate changes in the river’s morphology and geomorphic unit diversity. Additionally, Digital Elevation Model of Difference (DoD) and historical discharge data (1955-present) enabled the analysis of hydromorphological changes. Results showed improvements in morphological quality and geomorphic diversity, particularly in restored reaches compared to unrestored ones, highlighting benefits to river. Despite these successes, further research is needed to determine the project’s effectiveness in mitigating flood waves. The study contributes valuable insights into sustainable river management in alpine ecosystems, emphasizing adaptive strategies, and innovative restoration evaluation methods in the context of climate change and human pressures.
Bridging rivers and floodplains: Restoration efforts to improve lateral connectivity
GARCIA Evelyn, BUENDIA Cristina, BARDINA Mònica, ROVIRA Albert, MUNNÉ Toni
Spain
Short abstract : River systems worldwide are increasingly threatened by human interventions, leading to disruptions in natural flow regimes, sediment transport, and ecological integrity. In response, restoration efforts are prioritizing the reconnection of rivers with their floodplains to enhance hydromorphological processes and ecological resilience. This study examines two restoration projects on the Ter River in Catalonia, a system significantly impacted by hydrological alterations and sediment deficit due to human activities such as gravel mining and dam regulation. These impacts have led to pronounced riverbed incision, highlighting the need for targeted restoration efforts. The first project (Gambires), completed in 2022, focused on a river reach where a secondary channel had become almost entirely disconnected from the main channel due to severe riverbed incision. Restoration involved removing sediment from an island to reduce its elevation, redistributing the sediment into the riverbed, and reestablishing the connectivity of a secondary channel. The second project (Colomers), scheduled for 2025, will include enhancing lateral connectivity by upgrading a drainage infrastructure along the river embankment. This will promote the creation of secondary channels, improve floodplain connectivity, increase biodiversity complexity, and help control invasive exotic species. Together, these projects aim to restore hydromorphological functionality and the ecological integrity of the Ter River’s riparian corridor.
Second experiment to re-inject water into an old, dried-up branch of the Rhône “La Lône de Jonage”
VUYLSTEKE Simon, GUIBERT Marion, LAFONT Guillaume, AIRD Adeline, FAURE Jean-Pierre
France
Résumé : Le projet de remise en eau de la lône de Jonage a pour but de permettre la remise en eau d’un ancien bras du Rhône asséché à partir d’une prise d’eau sur le canal de Short abstract : The aim of the “Lône de Jonage” restoration project is to restore a dry anabranch of the Rhône River by reinjecting water collected from the Jonage diversion channel. The project is designed to recreate aquatic ecosystems along a 1.6 km stretch of the anabranch. It will also allow for satisfactory conditions (notably, higher piezometric and soil moisture levels) for ecosystems associated with wetlands connected to rivers (e.g. alluvial forests, wet meadows).
The implementation of this project must be preceded by large-scale experiments to determine ideal irrigation levels for a sustainable, long-term solution:
– Hydromorphological monitoring: Identification of the anabranch’s water flow and hydromorphological characteristics (flow distribution, flooded surfaces, infiltration, etc.). The project is unique in that the anabranch has no outlet. All water must be reinfiltrated into the sandy-gravel alluvium.
– Hydrogeological monitoring: Assessment of the impact of infiltrated water on the alluvial water table, as well as on the drinking water catchments of the Lyon metropolitan area.
– Ecological monitoring: Assessment of the ecological potential of the operation: characterization of environments and habitats, ecological inventories, impact on the alluvial forest.
The first results of this experiment will be finalized in spring 2025.
A component of the program to restore the Miribel Jonage section of the Rhône river, the project is managed by SYMALIM with financial support from the Water Agency (Agence de l’eau) Rhône-Méditerranée-Corse and EDF and in cooperation with state services and the following partners.
Development of scientifically-derived nature-based solutions in river engineering using the example of micro groins
MÜLLER Andreas C. T.
Germany
Short abstract : Using the example of micro groins, a multi-criteria research approach was developed to derive nature-based solutions for urban watercourses, which, in addition to the ecological objectives, also meets the use-related demands on the construction method and economic aspects. Initially, practical engineering knowledge is gained based on experience and implemented projects. Through the parallel study of natural processes in watercourses, the necessary interdisciplinary eco-hydraulic expertise of biologists, geo-ecologists and engineers is brought together. Potentially suitable construction methods are identified and compared for the urban boundary conditions. As the aim of this work is to transfer the findings into practice, state-of-the-art methods are used to investigate the prototypes. For this purpose, field experiments are carried out on reference projects and laboratory tests with a fixed and movable bed to assess the impact of the structures on the hydromorphological parameters. These are supplemented by numerical investigations for physical habitat modelling. The necessary derivation of design aids for practical use enables the future dissemination of the new construction methods.
Session B2 : River restoration: monitoring and evaluation
De-stonation: The effect of restored riverbanks on the macroinvertebrate communities of the Zandmaas (Sand Meuse) in the Netherlands
GARCIA VERAMATUS Maria Paz, DAUMAL Maya, PEETERS Edwin
Netherlands
Short abstract : Over the past 150 years, the Meuse River has undergone extensive man-made alterations, including channelization, flow regulation, water pollution, and stoning of riverbanks to prevent erosion. These alterations have significantly impacted aquatic macroinvertebrates, leading to the loss of typical riverine species, an increase in pollution-tolerant taxa, and the spread of exotic species. To restore natural processes and enhance habitat diversity, stone bank protections are being removed along sections of the Meuse River. The Zandmaas, the sandy section of the Dutch Meuse River, has been the focus of over half of the de-stoning projects that were performed between 2010 and 2021. However, the effects of these interventions on macrofauna biodiversity remain unclear. This study aims to assess the effect of completely de-stoned riverbanks on macrofauna biodiversity in the Zandmaas. Macroinvertebrates were sampled across five de-stoning projects, varying in age and extent of intervention. Sampling was conducted at the habitat level to evaluate how abiotic conditions, such as substrate diversity, influence macrofauna community structure.
Floodplain and channel restoration challenges in the Middle Ebro River
OLLERO Alfredo, PIRCHI Valeria N., GARCÍA LAGRANJA Juan Miguel, IBISATE Askoa, ALAMÁN Óscar, CAROZZA Jean-Michel, FERRER-BOIX Carles, JIMÉNEZ TORRECILLA Néstor, RODRÍGUEZ GALLEGO María, VALETTE Philippe
Spain
Short abstract : The Ebro River is a large Iberian watercourse that develops an extensive floodplain in its middle reach with frequent floods and flooding processes. Fluvial dynamics have been stabilised by regulation and defence works. The flood risk management paradigm has now been changed and some nature-based solutions are being implemented within the framework of the LIFE+ Ebro Resilience strategy and project. With a large interdisciplinary scientific team, the SEDEXCHARE Project evaluates this change in flood risk management from a hydromorphological and river restoration perspective. The achievements so far are scarce in restoration, but important in risk management. It is explained in which line actions should be increased to recover the river dynamics, proposing a territory of freedom for the river. Learning lines are also defined from the current diagnosis for a context of climate emergency and increase in extreme events. The recovered health of the river will provide territorial resilience to the floodable space, which includes population centres, agricultural uses and natural spaces.
The contribution of geophysics to the hydromorphological monitoring of an alpine river restoration: example of the upper Drac
RIBET Loïs, LIÉBAULT Frédéric, BORGNIET Laurent, WINIARSKI Thierry, MELUN Gabriel
France
Short abstract : The upper Drac is an alpine braided river that has been severely incised by gravel mining. The incision was particularly evident on a 3.5 km reach where major restoration work was carried out in 2014, in order to recreate a braided band and cover the lacustrine clays that had been unearthed as a result of the incision. Despite the effective re-establishment of a braided or wandering dynamic, the recurrent appearance of clay outcrops on the restored reach needs to be better taken into account when assessing the morphological trajectory of the site. It is therefore important to characterise the current thickness of the alluvial layer over these clays. The aim of this work is to present the initial results of a geophysical approach using Ground Penetrating Radar (GPR) for the hydromorphologyical monitoring of the restored reach of the Drac. In total, 3.5 km GPR profiles were surveyed simultaneously with a drone flight to locate the clay roof. The photogrammetric DEM and orthoimage obtained enable altimetric correction and better interpretation of the geophysical profiles. Preliminary results show that this method should enable (1) a good assessment of the current alluvial cover, and (2) a better characterisation of sensitive sectors with regard to the risk of reincision in the clays.
Post-works monitoring of groyne field removal in the bypassed channel of the Rhône River at Péage-de-Roussillon
ROCLE Mathieu, PRAT MAIRET Yves, PEETERS Alexandre, GUERIN Stéphane, MOIROUD Christophe
France
Short abstract : Following the large-scale removal of groyne fields (locally known as casiers Girardon) in 2014 in the bypassed channel of the Rhône River at Péage-de-Roussillon, a multidisciplinary monitoring program was implemented to assess the effectiveness of this ecological restoration, particularly in terms of sediment dynamics and changes in amphibian communities (fauna and flora typical of the restored habitats).
The gravel augmentation site and the rehabilitated active side channels were monitored using RFID technology. The results indicated that the observed mobility of tagged pebbles is variable and depends on their seeding position in the channel and the associated hydraulic conditions.
Vegetation monitoring identified significant regeneration of alluvial woodland in 2018. The spectacular diversification of habitats has also enabled the expression of heritage species.
The maintenance or even establishment of certain species is largely dependent on morphogenic floods, so the sustainability of the reactivation processes of alluvial margins will therefore depend on how often they occur in the future.
Dismantling lateral river structures to restore biodiversity: short-term effects on riparian plant communities
APPELTAUER Sina, EVETTE André, PIÉGAY Hervé, JANSSEN Philippe
France
Short abstract : On the Rhône, dismantling of lateral structures is being carried out to reactivate river dynamics and restore riparian plant communities on riverbanks. The effects of this work were monitored at 5 sites over three years and compared with reference and control sites. The taxonomic and functional response of plant communities was studied at site and quadrat spatial scales. The results show that restoration works have created topographic profiles that were higher relative to the waterline and with greater proportions of fine sediment than at the reference and control sites. In response, riparian communities at restored sites were closer to those at reference sites in the first year, but rapidly diverged towards those at control sites after three years. In addition, at the quadrat scale, the response of plant communities to the work was studied by comparison with quadrats from reference and control sites positioned under similar environmental conditions. Here too, the results showed rapid convergence of the plant communities in the restored quadrats towards those in the control quadrats. This illustrates not only the difficulty of restoring abiotic conditions close to those of reference and control sites, but also that the action of dismantling dykes alone cannot restore riparian plant communities characteristic of mobile sedimentary bars.
Restoring small streams: Effects on habitat complexity
WEBER Christine, SPRECHER Lucie, BEHNSEN Tara, HISCHIER Chantal M., THOMAS Gregor
Switzerland
Short abstract : Human impact leads to ecological simplification, also in small streams, where habitat complexity is considerably reduced by channelisation, draining of wetlands or excessive fine sediment input. Restoration measures are being implemented worldwide to restore habitat complexity in rivers and streams to maintain their exceptional blue-green biodiversity. Here, we compare 22 restoration projects in small mid-elevation streams in Switzerland with channelised control reaches that were surveyed by means of standardised methods. We use landscape metrics to assess habitat complexity in terms of substrate composition, river bed structures and presence of cover previously mapped in the field. Landscape metrics are tools commonly used in landscape (= terrestrial) ecology and can serve as proxies for ecosystem characteristics such as habitat connectivity or isolation, and organism dispersal. However, landscape metrics have rarely been applied to aquatic habitats, and their potential as indicators for outcome evaluation of river restoration remains largely understudied. Our preliminary results indicate positive restoration effects for several of the landscape metrics used, highlighting their benefit for monitoring and evaluation of river restoration.
Thinking generalization about ecological restoration: evolution of scientific practices in Rhône river studies
COUSIN Basile, COMBY Émeline
France
Short abstract : As part of the ecological restoration of the Rhône River which started in the late 1990s, a group of French and Swiss scientists set up the RhônEco program to assess its impact. After more than 20 years of research described as interdisciplinary and co-constructed between scientists and managers, the program was renewed in 2024, with a major thematic and methodological extension, accompanied by a significant change in its members. These changes seem particularly interesting to study from a Science and Technology Studies (STS) perspective, which has highlighted the importance of questioning scientific production in relation to the social, political and economic contexts in which it is embedded. The aim is to examine the potential evolution of scientific practices and discourses in this changing context. A campaign combining participant observation and semi-structured interviews (n=22) was carried out with scientists involved in the RhônEco program. The survey highlighted the emergence of a nomothetic epistemology, which relies mainly on bibliographical and theoretical contributions in the construction of its questions and methodologies, and aims to provide generalizing answers. This differs from the idiographic epistemology already present in the program, which is mainly based on an inductive approach associated with empirical observations, emphasizing the specificity of the Rhone River case study and aiming at a holistic understanding of the system.
Restoring small streams: Effects on aquatic organisms
SPRECHER Lucie, WEBER Christine, BEHNSEN Tara, THOMAS Gregor
Switzerland
Short abstract : The loss of biodiversity in aquatic ecosystems, including small streams, is a growing concern globally. In Switzerland, key drivers of biodiversity decline in rivers and streams include channelization, physical barriers, and deteriorating water quality. Restoration projects usually aim to enhance the abundance and diversity of aquatic organisms by implementing different types of measure, in particular by improving abiotic structures. However, studies report inconsistent findings regarding the effectiveness of river restoration in enhancing biotic communities. To explore these inconsistencies, we conducted a standardized survey of 22 restoration projects in small Swiss streams and channelized control reaches. Using a cross-project comparison, we examined biotic data (macrophytes, fishes, macroinvertebrates, and riparian vegetation) alongside abiotic parameters (habitat complexity, temperature, and catchment geodata). Preliminary analyses of a subset of projects (n=16) suggest an overall positive effect of river restoration, but with significant variation between individual indicators. Our findings will contribute to a better understanding of the efficacy of restoration to conserve blue-green biodiversity in small streams.