Synoptic observations of sediment transport and exchange mechanisms in the turbid Ems Estuary: the EDoM campaign

[摘要] An extensive field campaign, the Ems-Dollard Measurements (EDoM), was executed in the Ems Estuary,bordering the Netherlands and Germany, aimed at better understanding themechanisms that drive the exchange of water and sediments between a relatively exposed outer estuary and a hyper-turbid tidal river. More specifically, the reasons for the large up-estuary sediment accumulation rates and the role of the tidal river on the turbidity in the outer estuary were insufficiently understood. The campaign was designed to unravel the hydrodynamic and sedimentary exchange mechanisms, comprising two hydrographic surveys during contrasting environmental conditions using eight concurrently operating ships and 10 moorings measuring for at least one spring–neap tidal cycle. All survey locations were equipped with sensors measuring flow velocity, salinity, and turbidity (and with stationary ship surveys taking water samples), while some of the survey ships also measured turbulence andsediment settling properties. These observations have provided important new insights into horizontal sediment fluxes and density-driven exchange flows, both laterally and longitudinally. An integral analysis of theseobservations suggests that large-scale residual transport is surprisinglysimilar during periods of high and low discharge, with higher riverdischarge resulting in both higher seaward-directed fluxes near the surfaceand landward-directed fluxes near the bed. Sediment exchange seems to bestrongly influenced by a previously undocumented lateral circulation celldriving residual transport. Vertical density-driven flows in the outerestuary are influenced by variations in river discharge, with a near-bedlandward flow being most pronounced in the days following a period withelevated river discharge. The study site is more turbid during winterconditions, when the estuarine turbidity maximum (ETM) is pushed seaward by riverflow, resulting in a more pronounced impact of suspended sediments onhydrodynamics. All data collected during the EDoM campaign, but alsostandard monitoring data (waves, water levels, discharge, turbidity, andsalinity) collected by Dutch and German authorities are made publiclyavailable at 4TU Centre for Research Data ( https://doi.org/10.4121/c.6056564.v3 ; van Maren et al., 2022).

[学科分类] 眼科学