Density effects in the braakmanhaven

Sanne Poortman, Harmen Talstra, Abraham Bliek

Thursday 2 july 2015

8:30 - 8:45h at Europe 2 (level 0)

Themes: (T) Managing deltas, (ST) Saline and freshwater interaction

Parallel session: 10K. Managing deltas - Saline

The effects of density differences on the flow pattern in the entrance of the Braakmanhaven, a port in the well-mixed Scheldt estuary, have been investigated by means of field measurements and a non-hydrostatic three-dimensional numerical flow model named FINEL3D. Two modelling scenarios have been investigated: (a) with realistic salinity variations (as function of the tide) in the estuary, and (b) without salinity variation. This has provided insight how density differences in the Western Scheldt do influence the flow pattern in the port entrance. The realistic model simulation shows a three-dimensional flow pattern in the port entrance in good agreement with the measured current patterns. During the ebb period, outflow occurs in the upper part of the water column and inflow in the lower part of the water column. During the flood period these flow directions are reversed. The over-all spatial density variation is only limited. The simulated current pattern of the model run without salinity variation shows no three-dimensional effects in the port entrance and hence no agreement with the current measurements. The model simulations show that density differences in the Western Scheldt, though small, have a significant impact on the flow pattern in the entrance of the Braakmanhaven. Since the suspended sediment concentration in the incoming near-bed current is relatively high, small density differences over the tidal period are in fact an important factor for the siltation of the port. It is expected that small density differences are of importance as well for siltation processes in other ports along estuaries.