EGU2020-20649
https://doi.org/10.5194/egusphere-egu2020-20649
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

The Rance tidal power station: a preliminary study of its impact on tidal patterns and sediments dynamics in the Rance estuary (France) from 1957 to 2018

Rajae Rtimi1, Aldo Sottolichio2, and Pablo Tassi3
Rajae Rtimi et al.
  • 1Electricité De France (EDF) R&D, Saint-Venant Laboratory, Chatou, France (rajae.rtimi@edf.fr)
  • 2EPOC Laboratory, Bordeaux University, Talence, France (aldo.sottolichio@u-bordeaux.fr)
  • 3Electricité De France (EDF) R&D, Saint-Venant Laboratory, Chatou, France (pablo.tassi@edf.fr)

The Rance tidal power station (located on the Brittany coast of Northern France), was opened in 1966 as the world’s first and largest tidal power station, with peak output capacity of 240 Megawatts. It is currently the second world’s largest tidal power installation after the Sihwa Lake Tidal power station (South Korea). The power plant is located at the mouth of a small steep-sided ria, with a maximum perigean spring tidal range of 13.5 m and an average fluvial discharge of 7 m3/s. The dam is 750 m long and the tidal basin measures 22.5 km2. Despite a well-known effect of the plant on the damping of estuarine water levels, little attention has been given to the consequences of the dam in the estuarine environment in terms of hydrodynamics, for instance, the propagation of the tidal wave and tidal currents along the estuary are still little understood. Moreover, net siltation has been reported by several observations, but there is no specific knowledge on the role of the plant on sedimentation. In this study, we analyze the impact of the tidal power station on tidal wave patterns and sediment dynamics in this particular man-engineered system. To this goal, a numerical model based on a two-dimensional depth-averaged approach is implemented to predict the tide propagation and tidal currents along the estuary accounting for the presence of the tidal power station. Three modelling scenarios were performed: the first considering the bathymetry of 1957 (before the plant’s construction), a second scenario considering the bathymetry of 2018 without the presence of the power station and a third scenario considering the bathymetry of 2018 with the power station. Preliminary results showed that, with and without the tidal power station, the upper estuary exhibits a flood dominant behavior, with longer duration of falling water than rising water, and conversely the lower estuary is ebb dominant with shorter duration of falling water than rising water. This analysis also revealed that the tidal power station might switch the flood dominance in the central estuary to ebb dominance. These findings imply a net seaward transport of both coarse and fine sediments in the lower estuary. Therefore, the tidal power station might have a considerable role in modulating the estuarine turbidity maximum and channels’ morphology. Finally, these results are compared with preliminary numerical simulations of suspended sediment transport to further quantify the impact of the tidal power plant on the dynamics of the estuarine turbidity maximum.

How to cite: Rtimi, R., Sottolichio, A., and Tassi, P.: The Rance tidal power station: a preliminary study of its impact on tidal patterns and sediments dynamics in the Rance estuary (France) from 1957 to 2018, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20649, https://doi.org/10.5194/egusphere-egu2020-20649, 2020

Comments on the presentation

AC: Author Comment | CC: Community Comment | Report abuse

Presentation version 2 – uploaded on 04 May 2020
  • CC1: Comment on EGU2020-20649, Rory O'Hara Murray, 04 May 2020

    Great to see some work done on the impacts of this barrage. Is it still the largest in the world?  I’m occasionally asked about the impacts of barrages on physical processes (tides, wetting/drying etc.) but I’m not aware of much work on this – are you able to point me in the direction of any good published work?  Hopefully you’ll be publishing yours soon?

    • AC1: Reply to CC1, Rajae Rtimi, 05 May 2020

      Thanks for your comment. Now the Rance tidal power station is the second world's largest tidal power plant behind the Sihwa Lake tidal power station (South Korea). Indeed, there isn't much published work on this. In the context of the Rance TPP, there is Bonnot-Courtois et al ., Mont Saint-Michel Bay and the Rance estuary, 2002. And we will be publishing our work soon. Otherwise, there is some good published work on the Sihwa lake TPP : Young Ho Bae et al., Lake Sihwa tidal power plant project, 2010 and J.W. Kim, et al., Dynamics of sediment disturbance by periodic artificial discharges from the world's largest tidal power plant, 2017.

  • CC2: Comment on EGU2020-20649, Iain Fairley, 04 May 2020

    Really nice study! Can you explain why there seems to be open sections of channel either side of the barrage in the mesh that don't seem to exist in the aerial photo (slide 5)?

    • AC2: Reply to CC2, Rajae Rtimi, 05 May 2020

      Thanks for your comment ! Indeed, there is open channel section on each side of the tidal power station in the mesh. Actually, the aerial photo is a photo from above, it doesn't show what is bellow the road. The TPS is presented in the 2D model as an island, and we couldn't separate the upstream from the downstream of the TPS. Therefore, there is the small open sections on each side of the TPS. However, we assign a high bathymetry to these sections so that the water doesn't pass through. 

Presentation version 1 – uploaded on 03 May 2020 , no comments