Als de duinen breken: Once the Dunes Breach

Uittree redeAfscheidsrede, Uitgesproken bij het afscheid van het ambt van hoogleraar Kustwaterbouwkunde aan de Technische Universiteit DelftCoastal Engineerin

Kustverdediging na 1990 (Kustnota 1990): Technisch rapport 5: kustvoorspelling

Het beoogde resultaat van deze studie is een voorspel ling te geven van de ligging van de kustlij n in 1990, 1995 , 2000 , 20 10, 2020 , 2050 en 2090 . Niet aIleen het verlangde onderscheidend vermogen in de tijd is groot , ook het verlangde ru imtelijk oplossend vermogen is hoog: van de or de een kilometer. Deze vraagstelling is vooral bepaald door de eisen die de beleidsanalyse stelt; zij is niet ingegeven door de mogelijkheden die de technische kennis van het kustgedrag biedt . De technische haalbaarheid van de voorspelling wordt enigszi ns vergroot omdat bij de voorspelling van de kustligging er in eerste aanleg van kan worden uitgegaan dat het huidige kustbeheer wordt voortgezet , dat er geen grote civieltechnische ingrepen worden uitgevoerd, en dat de huidige stijgingssnelheid van de zeespiegel gehandhaafd blijft. Naast deze "basisvoor spelling" dienen ook voorspellingen te worden gedaan voor scenario 's met hogere stijgingssnel heden van de zeespiege l en ongunstiger meteorologische omstandigheden . De voorspellingen dienen te worden gebaseerd op een optimale kombinatie van de fenomenologische kenn is en de huidige fysische proceskennis.Kustnot

Effects of sea level rise on coastal evolution

Using the Dutch coastal evolution in the Holocene upto the present as an example and a test case, a coastal evolution concept is proposed and materialized with which shoreline position changes for different sea level rise scenarios are predicted. The (more generally applicable) model applies to (quasi-)uniform coastal stretches. It accounts for morphodynamic processes from the shelf to the first dune-row, and integrates over coastal units of approximately 10 km alongshore length. The added value compared to earlier published concepts or models lies in the full inclusion of cross-shore and alongshore processes, and in the distinction between a - with respect to sea level rise - instantaneously responding active zone and a noninstantaneously responding central shoreface zone. Relevant differences have been found to exist between closed and interrupted coastal stretches. An important conclusion is that the cross-shore effective Bruun-effect is only of limited importance. This is especially true in the case of the interrupted coast. Longshore sand transport gradients are very important there. This is mainly connected with the sand demand which is placed on coastal stretches adjacent.Hydraulic EngineeringCivil Engineering and Geoscience

Cross-shore Sediment Transport

In the first phase of the detailed nodelling of cross-shore sediment transport under random waves a model is constructed which adopts a vertically integrated transport description for sheetflow situations. The formulation of the transport as a function of the instantaneous velocity field is based on the approach of Bailard (1981). This approach assumes in essence simply that the instantaneous transport is proportional with some power of the instantaneous near-bottom velocity. Implementation of this transport description in a time-dependent model requires a formulation of the time-mean and some low order moments of the near-bottom velocity field. An ad-hoc formulation based on a monochromatic, second order Stokes wave representation is presented. A numerical research model, based on the above formulations, is described and limitedly checked on its performance on the basis of an available field data set. Some consequences for further study are indicatedHydraulic EngineeringCivil Engineering and Geoscience

Large-scale coastal behaviour in relation to coastal zone management

The development of coastal erosion management - addressing typical traditional erosion problems - towards coastal zone management addressing the evaluation of alternative solutions to guarantee a variety of coastal zone functions on their economic time scale - has necessitated the formulation of large-scale coastal evolution (LSCE) models. Using the coastal evolution of the Netherlands in the Holocene up to the present as an example and a test case, Stive et al (1990) formulated such a LSCE concept. The (more generally applicable) model applies to quasi-uniform coastal stretches. It accounts for morphodynamic processes from the shelf to the first dune-row, and integrates over coastal units of approximately 10 km alongshore length. The added value, compared to earlier published concepts or models, lies in the full inclusion of cross-shore and alongshore processes, and in the distinction between a - with respect to sealevel rise - instantaneously responding active zone and a noninstantaneously responding central shoreface zone. Relevant differences have been found to exist between coastal cells on the "closed" and the "interrupted" coast. An important conclusion is that the crossshore effective Bruun-effect is only of limited importance. This is especially true in the case of the interrupted coast. Longshore sand transport gradients are very large there. This is mainly related to the sand demand which is placed on coastal stretches adjacent to estuary mouths of those estuaries which tend to follow the sea-level rise.Hydraulic EngineeringCivil Engineering and Geoscience