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In deze rapportage worden de oostelijke, buitendijkse delen van de Nederlandse Waddeneilanden behandeld, de zgn. eilandstaarten. Wanneer deze volledig ontwikkeld zijn bestaat ze uit wadplaten, kwelders en duinen. Dit rapport behandelt de geomorfologie, waterhuishouding en vegetatie van eilandstaarten. De ontwikkeling van eilandstaarten is mede van belang voor de functie die ze hebben in de waterveiligheid.

Het Waddengebied krijgt de komende eeuw te maken met klimaatverandering. Naarmate de zeespiegel verder stijgt, vraagt het intergetijdengebied van de Waddenzee meer zand en onttrekt dat naar verwachting aan de buitendelta’s en de eilandkusten. Het is dan de vraag of het meegroeivermogen van het gebied voldoende is om de zeespiegelstijging bij te houden.

The report proposes a research framework which follows a learning-by-doing approach along the three research lines: monitoring & data analysis, system research & modelling and field experiments (pilots). All studies together will take several decades, partially due to the many questions, partially because studying changes in the system via the above-mentioned research lines takes time. Research programs developed on basis of this framework may focus on a part of the research issues

In dit rapport staan de Nederlandse kwelders en schorren centraal. Nederland heeft een bijzondere verantwoordelijkheid voor handhaving van de kwantiteit en kwaliteit van de drie betreffende habitattypen ‘eenjarige pioniervegetatie van slik- en zandgebieden met Zeekraal (Salicornia spp.) en andere zoutminnende soorten’ (H1310), meerjarige pioniervegetatie met Slijkgrassen (Spartina spp.) (H1320), en Atlantische kwelders en schorren (H1330). Dit rapport beperkt zich tot de vastelandkwelders. Deze kwelders zijn in grote mate menselijk beïnvloed en kunnen daarom het beste als halfnatuurlijk worden omschreven.

The article focuses on the morphological development of the Wadden Sea barrier island system, with emphasis on West and East Frisian islands on several temporal and spatial scales. In addition, it integrates the insights for management purposes. Barrier island management is addressed with respect to morphology, sediment budgets, safety and natural values. We show that each of these issues is determined to some extent to various spatio-temporal scales and that the management of a barrier island has to be considered in terms of interactions on various spatial and temporal scales. Morphology of some of the barrier islands is determined by the pre-existing Pleistocene relief to a fair extent, either directly due to erosion-resistant outcrops on or near the islands, or indirectly by determining the locations where inlet systems or estuaries could develop. Where this is not the case, the larger part of the sediments are locally reworked Pleistocene or Holocene deposits eroded at the North Sea coasts of the barrier chain and deposited in the back-barrier area and on the islands as a response to sea-level rise. Hardly any sand is coming in from outside the area. In order to keep up with sea-level rise sand has thus to be nourished if coastal retreat is not allowed. During the long Holocene evolution islands and ebb-tidal deltas have been lined up during their coastward migration, forming a more or less uninterrupted barrier chain along the Frisian coasts. The present-day approach of mainly focusing on the fixation of the inhabited parts of the chain will most likely result in a de-alignment of the various parts of the chain, resulting in increasing erosion of the promontories. An inlet system is a sediment-sharing system with a tidal inlet, the ebb-tidal delta, adjacent barrier islands and the tidal basin with channels, shoals, tidal flats and salt marshes. The sand balance of a barrier island is thus directly linked to tidal inlet system development. A natural change or an intervention in the sediment-sharing system by man may thus have repercussions for the island's development. Sediment redistribution in the coastal zone may also depend on climate, as is illustrated by the rapid growth of the islands after the demise of the Little Ice Age. On the barrier islands themselves many measures were taken during the past two centuries to ensure coastal safety. The successful attempts to stabilize the coasts and dunes of the barrier islands resulted in a reduction of sand transport from and along the shoreface to the beach and onto the islands. To some extent this has been restored by applying sand nourishments. However, vertical accretion of the islands is still largely impossible due to all the older coastal protection measures still present. On the long run sedimentary dynamics are essential if the island is to accrete vertically with sea-level rise, which forms a robust and sustainable strategy to guarantee safety during the next centuries. Massive stabilization also reduced the opportunities for pioneer vegetation. Dune belts and tidal marshes have experienced a fast succession resulting in a climax vegetation and the loss of the characteristic open landscape. In order to restore nature sufficient space and time should allow natural processes to develop and to create robust ecosystems. Instead of focusing on nature conservation a paradigm shift is needed in barrier island management towards stimulating the development of natural dynamics. To our opinion the best solution is to allow the geo-biological processes to take their natural course as much as possible. Examples are given for the various parts of a prototype barrier island. Only where this is not feasible other management practices should be applied. As a rule of thumb: soft and with respect for morphodynamical integrity where possible, hard where really needed. This concept applies both to the various morpho-ecological units on the islands and to the morphological developments on larger spatio-temporal scales. © 2012 Elsevier Ltd.

Dit rapport geeft een samenvatting van relevant onderzoek naar de golfreducerende werking van kwelders en schetst de randvoorwaarden voor kweldervorming. Kwelders vormen een zone in het intergetijdengebied die de golven beïnvloeden door de weerstand van de bodem en de kweldervegetatie. De golfreducerende werking is afhankelijk van de hoogte en breedte van de kwelder, maar ook van de optredende waterstanden. Het is nog onduidelijk in hoeverre kwelders een bijdrage kunnen leveren aan de waterveiligheid in een veranderend klimaat. De studie is verricht in opdracht van het Deltaprogramma Deelprogramma Waddengebied en vormt een stap in het verkennen van geschikte waterveiligheidsstrategieën in het Waddengebied die zich naast waterveiligheid richten op doelstellingen voor natuur en ruimtelijke kwaliteit.

The Rif and the Engelsmanplaat form together a supra- to intertidal flat-complex at the fringe of the ebb-tidal delta and the back barrier area in the Frisian Inlet, located between the Dutch Wadden Sea Islands Ameland and Schiermonnikoog. The complex divides the Frisian Inlet into the Pinkegat Inlet in the west and the Zoutkamperlaag Inlet in the east. During the last decades the Engelsmanplaat has been suffering from serious erosion. This paper presents a study meant to find the causes for the recent erosion, especially to answer the question if the erosion is related to the human interferences in the area. The study is based on literature survey, data analysis and modelling of hydrodynamic processes. It is concluded that the recent erosion fits into the pseudo-cyclic development of the intertidal flat complex. However, the period of erosion may have been longer than normal and the rate of erosion may have been higher than normal. It is also concluded that such abnormal development is probably effects of the closure of the Lauwerszee in 1969 and not due to land subsidence caused by gas mining.

Contains fulltext : 75236.pdf (Publisher’s version ) (Open Access) 6 p.

Historical maps of southwest Texel and the adjacent ebb-tidal delta, supplemented with quartz OSL (Optically Stimulated Luminescence) ages of dune sand, span four centuries and show several links between coastal development and ebb-tidal-delta behavior. Updrift inlet migration governed recurved-spit formation, and changes in ebb-tidal-delta size and shape resulted in the formation of a bulge at the island terminus. Sustained updrift migration of the ebb-tidal delta resulted in a commensurate position shift of the bulge and eventually in flattening of the coastline. Regional coastal-management measures have had a strong influence on tidal-inlet and ebb-tidal-delta behavior, and therefore also on the changing shape of southwest Texel. Identification of relationships between ebb-tidal-delta behavior and changing barrier-terminus erosion-and-accretion patterns on a decadal to century time scale contributes to our understanding of coastal-system dynamics. Any barrier terminus with preserved sets of dune ridges holds a potential record on past ebb-tidal-delta orientations, which provide clues on past changes in tidal prisms and wave versus tide dominance. Under the current ebb-tidal-delta configuration, the entire westward-oriented coast of southwest Texel is too exposed for lasting accretion. Bulges resulting from future merger of shoals with the coast in this area will be eroded rapidly. © 2006.

The Wadden Sea, along the coasts of The Netherlands, Germany and Denmark, forms one of the major nature reserves in western Europe and one of the major intertidal areas on Earth. Numerous observations are available from this highly dynamical area, collected over the many centuries that Man has been wrestling with the sea. The growing concern about the fate of the Dutch coast in the next century, when an increase of the rate of sea-level rise is expected, has recently triggered extensive interdisciplinary research on coastal dynamics. This offered the opportunity to study in detail the dynamics and development of the Dutch Wadden Sea system, especially of the Frisian Inlet. The central theme in this study is the detailed understanding, from a geologists' point of view, of the dynamics of the morphological and sedimentological development of the Dutch Wadden Sea on different temporal and spatial scales. Special attention was given to interactions and feedbacks between sedimentary processes, sedimentary deposits and morphological elements, in order to promote a more dynamic approach of fossil analogues.