In 2015 heeft Tocardo met een consortium van bedrijven in een van de zuidelijke doorstroomopeningen van de Oosterschelde-stormvloedkering (Roompot 8) een getijdencentrale gerealiseerd, die in december van dat jaar in gebruik is genomen. Het project Oosterschelde Tidal Power (OTP) waarvan hier verslag wordt gedaan, kent meerdere doelstellingen: de doorontwikkeling van de toegepaste technologie en het bereiken van een aanzienlijke kostenreductie. Een belangrijk onderdeel van het project is het monitoren van mogelijke omgevingseffecten op door de vergunningverlener relevant geachte natuurwaarden in de Oosterschelde en de aangrenzende Voordelta (zie Besluit vergunning Nb-wet 1998 van 16 december 2010; ref. DRZZ/2010-403). Het monitoringproject is zo opgezet dat daarmee niet alleen invulling wordt gegeven aan de vereisten vanuit de vergunning ex. de Wet natuurbescherming maar ook aan een breed vorm gegeven stakeholderproces. De aspecten die vanuit de vergunning moeten worden gemonitord zijn: effecten op de stroming en verandering in stroombeeld, vermindering getijdeamplitude en invloed op zandhonger (gevolg: afname intergetijdenareaal), aantalsontwikkeling van zeehonden en bruinvissen in het gebied, en mogelijkerwijs optredende directe effecten op individuele dieren zoals aanvaringen met turbines. In 2017 is additioneel een analyse van zeehonden-trackdata uitgevoerd, en in 2018 door Seamarco een academic position paper opgesteld, dat als Engelstalige bijlage aan deze rapportage is toegevoegd.

Net sediment transport in tidal basins is a subtle imbalance between large fluxes produced by the flood/ebb alternation. The imbalance arises from several mechanisms of suspended transport. Lag effects and tidal asymmetries are regarded as dominant, but defined in different frames of reference (Lagrangian and Eulerian, respectively). A quantitative ranking of their effectiveness is therefore missing. Furthermore, although wind waves are recognized as crucial for tidal flats’ morphodynamics, a systematic analysis of the interaction with tidal mechanisms has not been carried out so far. We review the tide-induced barotropic mechanisms and discuss the shortcomings of their current classification for numerical process-based models. Hence, we conceive a unified Eulerian framework accounting for wave-induced resuspension. A new methodology is proposed to decompose the sediment fluxes accordingly, which is applicable without needing (semi-) analytical approximations. The approach is tested with a one-dimensional model of the Vlie basin, Wadden Sea (The Netherlands). Results show that lag-driven transport is dominant for the finer fractions (silt and mud). In absence of waves, net sediment fluxes are landward and spatial (advective) lag effects are dominant. In presence of waves, sediment can be exported from the tidal flats and temporal (local) lag effects are dominant. Conversely, sand transport is dominated by the asymmetry of peak ebb/flood velocities. We show that the direction of lag-driven transport can be estimated by the gradient of hydrodynamic energy. In agreement with previous studies, our results support the conceptualization of tidal flats’ equilibrium as a simplified balance between tidal mechanisms and wave resuspension.

Idealized laboratory experiments have been conducted in a two-layer stratified fluid to investigate the leading-order dynamics that control submarine melting and meltwater export near a vertical ice-ocean interface as a function of subglacial discharge. In summer, the discharge of surface runoff at the base of a glacier (subglacial discharge) generates strong buoyant plumes that rise along the glacier front entraining ambient water along the way. The entrainment enhances the heat transport toward the glacier front and hence the submarine melt rate increases with the subglacial discharge rate. In the laboratory, the effect of subglacial discharge is simulated by introducing freshwater at freezing temperature from a point source at the base ofan ice block representing the glacier. The circulation pattern observed both with and without subglacial discharge resembles those observed in previous observational and numerical studies. Buoyant plumes rise vertically until they find either their neutrally buoyant level or the free surface. Hence, the meltwater can deposit within the interior of the water column and not entirely at the free surface, as confirmed by field observations. The heat budget in the tank, calculated following a new framework, gives estimates of submarine melt rate that increase with the subglacial discharge and are in agreement with the directly measured submarine melting. This laboratory study provides the first direct measurements of submarine melt rates for different subglacial discharges, and the results are consistent with the predictions of previous theoretical and numerical studies.