Seasonal and tidal variability of the hydrology and suspended particulate matter in the Van Uc estuary, Red River, Vietnam

Violaine Piton (1, 2) , Sylvain Ouillon (1, 2) , Vu Duy Vinh (2) , Gael Many , Marine Herrmann (1, 2) , Patrick Marsaleix (1)

1 LEGOS - Laboratoire d'études en Géophysique et océanographie spatiales
2 USTH - University of Science and Technology of Hanoi

This study explores the seasonal and tidal changes in flow and suspended matter dynamics in the tropical and macrotidal Van Uc River estuary (North Vietnam) and aims at understanding, among others, the sediment delivery to the ocean and the processes behind the estuary siltation. Four campaigns took place during the contrasting high flow and low flow seasons, for each during neap and spring tides. Water and suspended matter fluxes, salinity, turbidity and suspended sediment concentrations were measured for 24h at three cross sections along the estuary. During the high-flow season, the estuary was mixed, with seaward sediment flux during neap tide and ephemeral up-estuary sediment flux at spring tides due to tidal distortion. During the low-flow season, the system transitioned from partially mixed to highly stratified with salty waters intrusions, salt wedge presence and up-estuary sediment flux varying with the tidal regime. Estuarine siltation mostly occurred during low-flow at spring tides with a suspended matter inflow, primarily due to local resuspension, which represented ⅔ of the outflow. These findings also provide a new benchmark for hydro-sedimentary model calibration/validation.

Mots clés: suspended sediments; estuary; estuarine turbidity maximum; neap/spring cycle; Red River; Vietnam

Domaines: Ingénierie de l'environnement; Océan, Atmosphère

Violaine Piton, Sylvain Ouillon, Vu Duy Vinh, Gael Many, Marine Herrmann, et al.. Seasonal and tidal variability of the hydrology and suspended particulate matter in the Van Uc estuary, Red River, Vietnam. Journal of Marine Systems, 2020, 211, pp.103403. ⟨10.1016/j.jmarsys.2020.103403⟩. ⟨hal-03053185⟩