Research

The seventh research programme (OSR7) continue to meet the management issues redefined by scientists and operators in 2020. Research on the effects of climate change on hydro-sedimentary processes has been strengthened.

Focus A
To improve understanding of the hydro-sedimentary processes of the Rhône River (particularly sand dynamics) and to establish links with coastal hydro-sedimentary processes.  Research teams are developing in situ continuous measurements, sediment budgets and modelling of sand stocks and flows in the Lyon sector (Action A.1). Long-term assessment of the sedimentation of fine sediments is being completed, particularly in the delta, in conjunction with infrastructures development on the Rhône River (Action A.2). The monitoring of flows and stocks of fine sediments and sands during exceptional hydrological events is also planned, particularly for the APAVER 2025 (Action A.3).

Focus B
To improve knowledge about the sources and dynamics of suspended matters (MES) and associated contaminants to reduce the inputs. Research works aim to characterise the contamination (current and historical) of sediments with PFAS (Action B.1). The sources and future of contaminants discharged into the Rhône River continue to be studied, particularly in urban areas (Action B.2). Sediment tracing to refine the assessment of the contributions of the tributaries of the Upper Rhône to MES flows is also continuing (Action B.3). Finally, research will be carried out for the first time on the spatial characterisation of surface sediment contamination along the entire length of the Rhône River (Action B.4).

Focus C
To monitor effects of restoration actions to ensure their success, further enhance their beneficial effects and propose additional measures when the responses observed fall short of the objectives. Assessment of benthic habitats status in restored and non-restored sectors of the Rhône river is continuing (Action C.1). Research to assess the response of habitats to sediment inputs is being realized in link with the OSR (Action C.2). Special metrological efforts were making to measure sediment continuity (bottom sediments load) on different sites (sediment inputs sites, dams and weirs) (Action C.3). The impact of hydraulic infrastructures management and restoration actions on contaminant concentrations will also be studied (Action C.4). All these actions should provide feedback and operational recommendations for ecological restoration (Action C.5).

Focus D
To strengthen the definition of hydro-sedimentary scenarios incorporating climate change to better anticipate its future impacts. In particular, the challenge is to integrate erosion component into the J2000-Rhône hydrological model (Action D.1) and to model the transport of coarse sediments at the scale of the basin under scenarios of climate change and management of structures (Action D.2). Work is also underway to quantify the hydro-sedimentary impact of glacial melt and retreat (Action D.3), coupled with a field approach to assess the potential influence of this melt on inputs of suspended matters and contaminants (Action D.4). The results of the prospective modelling will be used and geo-visualised to make them more readily available (Action D.5).

Focus E
To continue the development of effective and innovative tools for transferring the data and knowledge. This involves maintaining and consolidating the monitoring network of suspended matters and contaminants flows and stepping up the banking of samples (Action E.1). Hydro-sedimentary modelling of the Rhône River from Lake Geneva to the sea is continuing (Action E.2). Data banking and sharing will continue (Action E.3), as will the general promotion and transfer of the scientific and technical advances of OSR (Action E.4).

After 12 years of research, the OSR’s scientific and operational partners were able to assess the progress of knowledge on hydro-sedimentary processes. They also redefine a research strategy to meet the new issues of sediment management. The sixth research programme implements this new strategic vision.

Focus A
To improve understanding of the hydro-sedimentary functioning by filling certain knowledge gaps. Measuring and quantifying the sand load remains a major challenge for researchers (Action A.1). The study of the link between morphological changes and the risk of flooding is also being strengthened (Action A.2) and the analysis of the fine sedimentation in the riverbed, dam reservoirs and alluvial margins is being continued (Action A.3). At the Rhône River mouth in Mediterranean Sea, particular attention is being paid to the link with the dynamics of the salt-water penetration and sediment dynamics (Action A.4).

Focus B
To improve knowledge of the dynamics of suspended matters (MES) and associated contaminants. This involves identifying unidentified sources of contaminated suspended matters, particularly in urban areas (Action B1). The research teams are also continuing to identify and characterise emerging contaminants (Action B2) and are studying the dynamics of their storage in sediments stocks (Action B.3). They are also looking at the behaviour of contaminants to determine their persistence in the Rhône River (Action B4).

Focus C
To monitor the effects of hydro-sediment restorations. The aim of the research is to characterise the benthic habitats status of the Rhône River (Action C1) and to assess the response of these habitats to sediment inputs (Action C2). Work is also being carried out to estimate the sustainability of the sediment inputs (Action C3). Based on this work, the researchers will be able to formalise feedback and formulate recommendations for improving practices (Action C.4).

Axe D
To forecast changes in hydro-sedimentary processes to anticipate their impact. The aim of the OSR researchers is to identify scenarios of future environmental changes, particularly climate change (Action D.1), on which to base prospective modelling of hydrological transfers (Action D.2), sedimentary transfers (Action D.3) and contaminants transfers (Action D.4).

Focus E
To continue the development of effective and innovative tools for data acquisition and knowledge transfer. The maintenance of the sediment flow monitoring network (Action E.1) and hydro-sediment modelling of the Rhône from Lake Geneva to the Mediterranean (Action E.2) remain key areas of work for the OSR. The researchers are also continuing data banking (Action E.3) and promotion of research results to Rhône River stakeholders (Action E.4).

The 5th research programme (OSR5) continues research activities of previous programs. After more than a decade of observations, major efforts are made in terms of instrumentation, methodological development or synthetic analyses to deepen our understanding of sediment processes.

Focus A
To assess the feasibility of revitalizing alluvial margins of the Rhône River. The research objective is twofold: to understand the process of fine sedimentation in alluvial margins and assess the risks of contaminants release (Action A.1), and to identify sediments transport conditions in order to optimize revitalization operations (Action A.2).

Focus B
To maintain the network for monitoring flows of suspended matters (MES) and associated contaminants. This involves guaranteeing the continuity of maintenance of the network’s stations (Action B.1), setting up event-based monitoring of flows of suspended matters and contaminants during flushing and flooding (Action B.2) and reinforcing metrology for sand monitoring (Action B.3).

Focus C
To provide deepen knowledge to diagnose the functional state of the Rhône. Research will enable researchers to refine interpretations concerning the tracing and identification of MES sources and the methodology for assessing spatial trends in contamination (Action C.1). An analysis of temporal trends in historical contamination is carried out (Action C.2). An analysis of contaminant flows in the dissolved and particulate phases is also carried out (Action C.3). In terms of morphodynamics, researchers have modelled and assessed the hydraulic effects of bed morphological changes (Action C.4). Finally, efforts have been made in the metrological field, notably to improve the sampling efficiency of “sediments traps” and to carry out geophysical acquisitions in large river (Action C.5).

Focus D
To enhance modelling and improve digital tools for data banking and diffusion. The development of the 1D hydro-sedimentary model remains a major transversal action (Action D.1). The BDOH database continues to be improved, particularly for flow calculations (D.2). Work is also underway to integrate OSR data into a Web-GIS system (Action D.3). Data banking continues (Action D.4).

Focus E
To ensure the coordination and animation of the OSR and reinforce the valorisation of its results.

The fourth research programme (OSR4) continued the works undertaken since 2009. The scientists proposed a reorganization of the research themes adapted to the new needs of operational staff and promoted interdisciplinarity within the observatory.

Focus A
To continue research on channel sediments load characterization and modelling. Quantifying the sand load in the Rhône is a new methodological objective (Action I.1). Research is focusing on t Rhône River sections which have still active sediments transport (Action I.2). Researchers are also looking at the channel’s response to the first sediment inputs undertaken on the Rhône River (Action I.3). More fundamentally, the teams are modelling long-term changes in the channel (Action I.4) and characterizing the morphodynamics of the river mouth in Mediterranean Sea (Action I.5).

Focus B
To refine understanding of sedimentation processes in the major riverbed. La dynamique de sédimentation des marges fluviales est étudiée en lien à différents enjeux de gestion (environnementaux, contamination, risque d’inondation) (Action II.1). Les équipes de l’OSR4 participent à la définition de l’état initial des sites, avant le début des travaux de démantèlement des marges (Action II.2). Les patrons de sédimentation enregistrant l’historique des flux et les variations longitudinales sont établis (Action II.3). Ce travail permet de proposer une vision globale de la sédimentation des marges à l’échelle des Rhône court-circuités (Action II.4)

Focus C
To ensure continuity of sediment flows monitoring network on the Rhône and its main tributaries. The aim is to continue and improve the observation and quantification of these flows (Action III.1). A special study is about the granulometric representativeness of the samples collected (Action III.2). Measurements from the monitoring network are also used to establish sediment flow balances at different time scales (Action III.3). They also provide a better understanding of the hydrological determinants of the sediment flows measured (Action III.4).

Focus D
To determine the origin of sediments (Action IV.1) and contaminants (Action IV.2) in transit in the Rhône from a spatial and temporal perspective. This involves continuing to develop tracing methods, defining transport processes and identifying contaminant transfer routes. Particular attention is being paid to the study of priority and emerging contaminants (Action IV.3) and their integration into the monitoring network (Action IV.4).

Focus E
To improve modelling, by implementing bedload and morphodynamics in models (Action V.1), by developing evolution scenarios (Action V.2) and by comparing the existing models (Action V.3). OSR4 has also enabled researchers to enhance the tools for managing data and displaying knowledge (Action V.4), and to continue coordination missions to encourage and facilitate dialogue and exchanges between the various OSR partners (Action V.5).

The third action programme (OSR3) represents a transitional period in the activities of the OSR. During this period, the research teams consolidated the scientific achievements of the first years of activity and prepared, in discussion with the partners of the Rhône Plan, the implementation of a new multi-year research programme in line with the objectives of the second Rhône Plan (2015-2020).

The one-year OSR3 programme ensured continuity in the measurement of the suspended maters and contaminants, in the analysis of sedimentation in the river major bed and backwaters, in the study of gravel bed load, in the improvement of the 1D sediment model, and in data banking.

The second action programme (OSR2) was carried out over three years. It aims to provide a state of knowledge on sediment dynamics in the Rhône River and to start continuous measurements of sediments. During the OSR2, scientific teams worked along 3 thematic focuses.

Focus A
To characterize sediment stocks in the channel, dam reservoirs and riversides of the Rhône. Research focuses on analysing the geometric evolution of the river corridor (Action 1) and characterizing the sediment continuum along the entire length of the Rhône River (in particular knowledge of the granulometric in channel) (Action 2). Specific work is being carried out on the bottom load at the mouth of the Grand Rhône (Action 3). The question of polluted sedimentary stocks and their fate is also being addressed (Action 4). Finally, OSR2 has led to the finalization of a “Master plan for reactivating the fluvial dynamics of the Rhône margins” (Action 5).

Focus B
To set up metrology tools to measure sediment flow. The measurement stations network for monitoring suspended matter and contaminants has been strengthened (Action 6). Researchers have also start work on the origin of sediments and contaminants (Action 7). In addition to continuous observations, measurements are taken during exceptional events (flooding and dam flushing) (Action 8). The OSR2 teams have initiated a methodological study to monitor and quantify gravel bed load (Action 9). Finally, new developments have been made in 1D modelling of sediment transfers (Action 10).

Focus C
To develop common tools for banking and visualizing OSR data. The management of data produced by the OSR is an important workstream (Action 11), as is the dissemination and promotion of research results to partners and Rhône River stakeholders (Action 12).

Initiated in 2009, the Rhône Sediment Observatory began with a one-year programme (OSR1). The aim was to consolidate the scientific community and start the first research actions in line with the issues of the Rhône Plan (2007-2013). OSR1 focused on:

Focus 1
To analyze morphological changes in riverbeds in relation to different types of infrastructures development (Girardon system (dykes and groynes, short-circuited Rhône River by-passing for hydroelectricity) and define a methodology for drawing up a “Master plan for reactivating the fluvial dynamics of the Rhône margins”.

Focus 2
To establish an inventory of existing hydro-sedimentary measurement stations, consolidate and complete this metrological network to measure sediment flows along the Rhône River and its tributaries.

Focus 3
To study the links between Rhône River infrastructures developments and sediment storage dynamics. Several studies are underway to determine the channel geometry and sediment volumes trapped upstream of dams, to determine the processes and origins of sediment deposits in river backwaters, and to reconstruct the history of contamination on a sediment fill associated with the installation of a dam.