Temporal and spatial dynamic of suspended sediments fluxes and sources and morphological evolution of the bed in the middle Loire river

The middle Loire riverbed, after its confluence with Allier, is characterised by a morphology of alternate bars more or less vegetated and possesses riverbank flood protections. The suspended particulate matter (SPM) fluxes are therefore originated from these two catchment areas that drain the eastern and southern parts of the Massif Central. The temporal dynamics of the SPM fluxes are very variable, both on an interannual scale and on the scale of a flood event. Furthermore, SPM fluxes also present high spatial heterogeneities as they are governed by complex processes of production (erosion) and transfer (storage/remobilisation). The Loire river plays an important role in supporting the French energy production by providing cooling water to several Nuclear Power Plants (NPP). However, the cooling systems of the NPPs on the middle Loire are exposed to the risk of silting. In order to ensure a safe management of water intakes and prevent the industrial risks arising from sediment transport, it is therefore imperative to understand the spatio-temporal dynamic of sediment production and transfer.

In this context, the objective of this thesis work is to provide keys to improve sediment management of the river between the two NPPs of Belleville and Dampierre. In a first place, the river flow and SPM data available at the upstream NPP of Belleville will be analysed in order to understand the temporal variations of the incoming SPM fluxes. In a second phase, a soil erosion and hydrological model will be implemented to understand the production processes in the upstream catchments. This second part will allow to determine the interactions of the SPM inputs in the river with the morphodynamics of the bed of the Loire between the two stations. We will present the methodology that has been designed to apprehend these two phases and the first results of the river SPM temporal dynamic at the Belleville NPP station.