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Portal > Offres > Offre UMR6118-DIMLAG-001 - Modélisation numérique de la dynamique des rivières impactées par des apports catastrophiques de sédiments (H/F)

High-resolution modeling of river response following catastrophic sediment release (M/W)

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Français - Anglais

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General information

Reference : UMR6118-DIMLAG-001
Workplace : RENNES
Date of publication : Friday, November 08, 2019
Type of Contract : FTC Scientist
Contract Period : 28 months
Expected date of employment : 1 January 2020
Proportion of work : Full time
Remuneration : 2617 € to 3729 € gross monthly salary according to experience
Desired level of education : PhD
Experience required : Indifferent

Missions

Catastrophic sediment release in fluvial systems is largely driven by landsliding which occurs naturally during large earthquakes or climatic events in mountain belts, but can also be caused by the failure of tailing dams or ash ponds releasing sediment that can be heavily polluted. Following a catastrophic release, the channel geometry will significantly vary and a full 2D morphodynamic modelling of river response is needed to predict the associated downstream hazards (change in flooding risk, bank erosion, channel avulsion, pollution). Eros, a 2D numerical model developed in Rennes1,2, has been used to study this response in the context of co-seismic landslide export and hazards prediction and using a single effective grain size 3,4. Yet, in natural systems, grain sizes can vary over several order of magnitude and are evolving during transport. In the context of channel morphodynamics, coarse grains and fine grains do not drive channel aggradation in similar ways, and the preferential elevation of deposition varies also with flood discharge. Grain entrainment is also modified by the complex nature of the channel bed and it remains debated whether using a single grain size is a severe limitation in fluvial morphodynamics or not. This project aims at developing a new multi-grain size approach in the Eros model, and use it to explore the morphodynamic response of rivers to large sediment inputs and the dispersion rate and patterns of the various grain sizes.

Activities

- Develop a multi grain size component in the landscape evolution model EROS with the ability to capture the transport of suspended, bedload material and pluri-metric blocs over decadal to centennial timescales.
- Evaluate the influence of the grain size distribution on the magnitude and duration of fluvial morphodynamics response to post earthquake increases in sediment supply.
- Predict the downstream dispersion and resident time of fine material in rivers and floodplains following catastrophic sediment release by landslides or dam.
- Disseminate results via peer-review publications and attendance of international conferences
- Collaborate with other postdoctoral researchers and PhD students in our team and Victoria University Wellington.

Skills

- PhD in Civil or Environmental Engineering, Hydrology, Earth Science, Physics, Mathematics, Geography or equivalent
- Previous experience with developing or using numerical models of fluvial sediment transport, river morphodynamics or landscape evolution
- Experience with programming (e.g., Matlab, Python, R, C/C++…)
- Willingness to spend a few weeks per year in Wellington, New Zealand
- Creative, critical, analytical and innovative mindset
- Ability to work independently
- Excellent written and oral communication skills in English (note: speaking/writing French is not mandatory)
- Willingness to work with PhD students
- Proven research experience in scientific publications

Work Context

This post-doctoral project is co-funded by a New-Zealand led international research project “Kaikoura earthquake-induced landscape dynamics”, and by the Brittany regional council in France. The work will be conducted at Geosciences Rennes (UMR CNRS 6118/University Rennes 1) and will be coordinated by Dimitri Lague (fluvial geomorphology & lidar remote sensing) and Philippe Davy (numerical modelling of fluvial systems), in collaboration with Jamie Howarth (extreme events geomorphology, Victoria University Wellington, New-Zealand).

The researcher will be hosted in th Dynamics, Imagery and Modeling of Environmental Systems (DIMENV) team which is a 50+ team articulated around 4 research groups: geomorphology, hydrological resources, biogeochemistry, sub-surface geophysics. Currently hosting 2 ERC starting grants, 1 Marie-Curie ITN, several Marie-Curie Post-doc fellows, a joint private-public laboratory (Fractory) and several ANR research projects, the team is highly international and multidisciplinary (geosciences, hydrology, physics, biogeochemistry, remote sensing, computer sciences). The post-doc researcher will be hosted in the Geomorphology group which has a strong track record in numerical modelling (EROS), experimental studies and high-resolution lidar data acquisition and processing. He is expected to participate in other team research projects such as the ERC Feasible led by P. Steer on earthquake geomorphology, the topo-bathymetric airborne LiDAR platform led by D. Lague (whose data will be used in the modelling project), the fractory led by P. Davy or the ANR SUCHY led by Joris Heyman on hyporheic zone physico-chemical dynamics.
New-Zealand project website: https://www.gns.cri.nz/Home/Our-Science/Natural-Hazards-and-Risks/Landslides/Research/Quake-induced-landslides

Bibliography on Eros
1. Davy, P., Croissant, T. & Lague, D. A precipiton method to calculate river hydrodynamics, with applications to flood prediction landscape evolution models, and braiding instabilities. J. Geophys. Res. 122, 1–22 (2017).
2. Davy, P. & Lague, D. Fluvial erosion/transport equation of landscape evolution models revisited. J. Geophys. Res. 114, F03007 (2009).
3. Croissant, T., Lague, D., Steer, P. & Davy, P. Rapid post-seismic landslide evacuation boosted by dynamic river width. Nat. Geosci. 10, 680–684 (2017).
4. Croissant, T., Lague, D., Davy, P., Davies, T. & Steer, P. A precipiton-based approach to model hydro-sedimentary hazards induced by large sediment supplies in alluvial fans. Earth Surf. Process. Landforms (2017). doi:10.1002/esp.4171

Additional Information

Rennes, the 8th largest city in France, is a lively student city in the western part of France, within 1h30 by fast train from Paris, and set in the beautiful Brittany region. Beautiful beaches and rocky coasts are within 1 hour.

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