Huisman, B.J.A., Sirks, E.E., van der Valk, L., Walstra, D.J.R., 2014. Time and spatial variability of sediment gradingin the surfzone of a large scale nourishment. In: Green, A.N. and Cooper, J.A.G. (eds.), Proceedings 13th International Coastal Symposium (Durban, South Africa), Journal of Coastal Research, Special Issue No. 70, pp. 127–132–134, ISSN 0749-0208.
Temporal and spatial variations in sediment gradation in the surfzone were investigated for a large scale nourishment (Sand Motor) at the Dutch coast (~ 21.5 million m3 sand). This nourishment provides an excellent opportunity to investigate the effect of hydrodynamic conditions on the spatial and temporal development of sediment grading. A strong point of the Sand Motor is that it has a well-known initial sediment composition. Measurements of the sediment grading at the Sand Motor were carried out during and after its construction to investigate the sorting process. Samples were taken for six cross-shore rays at ten depth contours (from MSL -1m to MSL -10m). A weighted average of the grain size distribution was determined for each cross-shore transect to investigate the alongshore sorting process. Similarly, cross-shore averaged sediment properties were determined for the samples above and below MSL -4m to assess the cross-shore sorting process. The sieved samples showed that: (1) significant sediment sorting takes place across the surfzone of the Sand Motor. Typically, the sediment in the surfzone of the exposed part of the Sand Motor is 20 to 30% coarser than the average for the survey; (2) a large depositional area with relatively fine material (150 to 200 μm) from the Sand Motor has developed on the Northern side of the Sand Motor; and (3) an alongshore band with finer sediment was found at water depths of 4 to 6 meter below MSL as a result of selection processes at the waterline.
