Newsletter #3 November 2008

Floating particles during sand mining for expansion of the Port of Rotterdam

spaceOn 1 Sept, the mining of 300 million cubic meters of sea bottom sands containing 1.5-2.5 % intercalated mud for the extension of the Port of Rotterdam started. This can potentially change instantaneous suspended particulate matter (SPM) concentrations along the Dutch coast. Therefore, Port of Rotterdam has asked IVM and Deltares to generate information on SPM concentrations before and during sand mining.

Increases in the concentrations of floating particles of clay, silt and organic material can change conditions for marine life directly, but also indirectly because these particles scatter and absorb sunlight and thereby influence the underwater light climate.

To be able to identify changes the natural SPM concentrations and their variability need to be established first. We opted for an advanced combination of IVM’s remote sensing products, and simulation modelling in data assimilation system that is being developed by Deltares. This is challenging, because it requires description of the entire mass-conservative mud-exchange system: this comprises more than the remotely sensed surface layer or even the entire water column. However, IVM’s HYDROPT algorithm and improvements on the bed-water exchange in sediment transport modelling (Deltares) allow realistic descriptions of water quality parameters and attenuation of light in the water. First results from the new data assimilation system have already resulted in a stable re-analysis of the surface SPM concentrations. Validation and skill assessment with in situ measurements confirmed that the assimilated data product is closer to the validation data than the results of a model without assimilation, and that the assimilation provides continuous information in time and space where remote sensing and in situ observations do not.

IVM and Deltares proved that the data assimilation approach is feasible. Now that the extension has started, Port of Rotterdam, IVM and Deltares will continue their collaboration to implement this approach that has the potential to greatly improve our knowledge of SPM transport in the Dutch coastal zone.