2 research outputs found
Synoptic observations of sediment transport and exchange mechanisms in theturbid Ems Estuary: the EDoM campaign
Synoptic observations of sediment transport and exchange mechanisms in the turbid Ems Estuary: the EDoM campaign
An extensive field campaign, the Ems-Dollard Measurements (EDoM), was executed in the Ems Estuary,
bordering the Netherlands and Germany, aimed at better understanding the
mechanisms 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 and
sediment 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 these
observations suggests that large-scale residual transport is surprisingly
similar during periods of high and low discharge, with higher river
discharge resulting in both higher seaward-directed fluxes near the surface
and landward-directed fluxes near the bed. Sediment exchange seems to be
strongly influenced by a previously undocumented lateral circulation cell
driving residual transport. Vertical density-driven flows in the outer
estuary are influenced by variations in river discharge, with a near-bed
landward flow being most pronounced in the days following a period with
elevated river discharge. The study site is more turbid during winter
conditions, when the estuarine turbidity maximum (ETM) is pushed seaward by river
flow, resulting in a more pronounced impact of suspended sediments on
hydrodynamics. All data collected during the EDoM campaign, but also
standard monitoring data (waves, water levels, discharge, turbidity, and
salinity) collected by Dutch and German authorities are made publicly
available at 4TU Centre for Research Data (https://doi.org/10.4121/c.6056564.v3; van Maren et al., 2022).</p