“Hydro sedimentary and morphodynamic evolutions of the Somme Bay

 using a multi-scale and multi-sensor approach”

The estuaries and bays of the English Channel are very dynamic environments, under the combined action of strong tidal currents and swell climate, and are concerned with dense human activities. Hydraulic works realized during the previous centuries (channeling, embankment, land reclamation) have accentuated the unbalance of sedimentary fluxes between the bays and the coastal zone and it has thus favored strong sedimentation inside the bays. This sedimentation provides protection against coastal erosion. However, the rise in mean sea level could increase the risk of submersion and lead to stronger swell levels and, thus, cause a reversal of the sedimentation phenomenon, promoting erosion in front of the dykes and destabilization of the littoral barriers. The Somme Bay (North of France) is a sandy estuary mouth exposed to strong tidal (> 8m in spring tides) and swell conditions and with a low river flow (less than 30 m3/s). This bay fills with fine sands with a current rate up to 0.37 ±0.17 m in the lowest parts of the intertidal zone. However, at short time-scales (e.g. annual), the sediment budget can be variable, and some sectors of the bay can display erosion.

The general objective of the thesis is to improve knowledge and comprehension of the main mechanisms controlling the sediment transfer, between the bay and the adjacent coastal zone and within the bay, and its morphodynamic evolution from monthly to multi-annual time steps. The methodology will be based mainly on in situ surveys to characterize the sedimentary and morphodynamic variability of the bay in response to hydrodynamic and meteo-marine forcings. The PhD candidate will combine multi-scale measurements (from the scale of the storm event to the multi-year period, from the dune field to the bay as a whole) and, in fact, multi-sensors (e.g. satellites, LIDAR, bathymetry, hyperspectral camera, and various hydro-sedimentary sensors) including the use of numerical simulations, calibrated and validated using these measurements.

Special attention will be paid on:

● the local interaction between waves-currents, morphodynamics and sediment transport,

● transport modality between the coastal area, the intertidal covering up to 80 % of the bay, the subtidal channels and the most upstream part enduring severe sediment settling,

● the variability of the sediment fluxes according to the different time-scales (tide, fortnight, seasonal, annual and pluriannual)

● the morphodynamic evolutions over several years (5-10 years) by reckoning the whole physical processes and their interactions.

The Phd student will be located at M2C Rouen under the supervision of Julien Deloffre (M2C), Sophie Le Bot (M2C) and Nicolas Huybrechts (Cerema).

Required profile:

Engineer or master degree in geosciences and/or coastal oceanography.

Knowledge of coastal or marine environments, in sedimentology (cohesive/non cohesive), sediment dynamics and fluid mechanics.

Experience in satellite imagery analysis, in situ measurements and/or data analysis will be appreciated.

Autonomy, critic and curious mind.

Application / Audition: Please send a CV, a motivation letter and 3 referees to : Cette adresse e-mail est protégée contre les robots spammeurs. Vous devez activer le JavaScript pour la visualiser., Cette adresse e-mail est protégée contre les robots spammeurs. Vous devez activer le JavaScript pour la visualiser., Cette adresse e-mail est protégée contre les robots spammeurs. Vous devez activer le JavaScript pour la visualiser.

Deadline for application: April 1st 2023

Audition : beginning of May


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