Grain size variations along cross-shore profile Katwijk of Holland coast

■ Cross-shore grain size variations have been observed along many coasts, Selective sediment transport and sorting processes, leading to grain size variations, occur when the cross-snore profile consists of graded sediment Each grain size fraction within a mixture of sediment responds differently to the same hydrodynamic regime; the basic rule is that finer grains are winnowed horn the bed in the most energetic areas by turbulent processes and are carried away to less energetic areas, resulting in coarsening of the bed in the more energetic areas. Terwindt (1962) studied cross-shore grain size variations for the location Katwijk along the Holland coast before and after a (minor) storm event The field results are discussed and compared to computational results öf a cross-shore mathematical model, for graded sediments. The cross-shore model represents the hydrodynamics, the sand transport rates, per size fraction and the bed evolution. The effect of a minor storm on the bed material composition (coarsening effect) along the barred cross-shore profile of Katwijk can be reasonably well simulated by the model.