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Lelystad, Netherlands

Arens S.M.,Arens Bureau for Beach and Dune Research | Arens S.M.,Technical University of Delft | Mulder J.P.M.,Deltares | Mulder J.P.M.,University of Twente | And 3 more authors.
Geomorphology | Year: 2013

This paper discusses and compares results of management interventions to remobilise dunes and obtain more autonomous changes in foredunes resulting from a change in coastal defence policy. In recent decades, nature conservation managers tried to restore aeolian dynamics and dune mobility landward of foredunes to maintain threatened, rare pioneer species. Results indicate that destabilisation activities yielded an important increase of blowing sand and its effects on ecology but with a limited effect on the desired integral remobilization of dunes. Roots remaining in the sand after removal of vegetation and soil is one of the main problems. Follow up removal of roots for 3 to 5. years seems to be essential, but it is not clear whether the dunes will remain mobile in the long term.In 1990 the Dutch government decided to maintain the position of the coastline by artificial sand nourishment. An intensive management of the foredunes was no longer required. Consequently, natural processes in the foredunes revived, and the sediment budget of the beach-dune system changed. Two main types of responses are visible. In some areas, increased input of sand resulted in the development of embryonic dunes seaward of the former foredunes, leading to increased stabilisation of the former foredunes. In other areas, development of embryonic dunes was insignificant despite the increased sand input, but wind erosion features developed in the foredunes, and the environment was more dynamic. The reasons for the differences are not clear, and the interaction between shoreface, beach and dunes is still poorly understood.Until now, attempts to mobilise the inner dunes were independent of changes made to the foredunes. We argue that an integrated, dynamic approach to coastal management, taking account of all relevant functions (including safety and natural values) and the dune-beach system as a whole, may provide new and durable solutions. An integrated approach would ideally provide fresh sand to the system by sand nourishment; define a wide safety zone, which enables the transition zone of beach to foredunes to develop freely; reserve space for natural processes without restrictions; and stimulate natural redistribution of sand within the system and restore inland transport of sand by removing vegetation behind the foredunes. A long time scale (several decades) is needed for this approach to be successful. © 2012 Elsevier B.V. Source


Leewis L.,VU University Amsterdam | van Bodegom P.M.,VU University Amsterdam | Rozema J.,VU University Amsterdam | Janssen G.M.,VU University Amsterdam | Janssen G.M.,Center for Water Management
Estuarine, Coastal and Shelf Science | Year: 2012

Coastal squeeze is the largest threat for sandy coastal areas. To mitigate seaward threats, erosion and sea level rise, sand nourishment is commonly applied. However, its long-term consequences for macroinvertebrate fauna, critical to most ecosystem services of sandy coasts, are still unknown. Seventeen sandy beaches - nourished and controls - were sampled along a chronosequence to investigate the abundance of four dominant macrofauna species and their relations with nourishment year and relevant coastal environmental variables. Dean's parameter and latitude significantly explained the abundance of the spionid polychaete Scolelepis squamata, Beach Index (BI), sand skewness, beach slope and latitude explained the abundance of the amphipod Haustorius arenarius and Relative Tide Range (RTR), recreation and sand sorting explained the abundance of Bathyporeia sarsi. For Eurydice pulchra, no environmental variable explained its abundance. For H. arenarius, E. pulchra and B. sarsi, there was no relation with nourishment year, indicating that recovery took place within a year after nourishment. Scolelepis squamata initially profited from the nourishment with "over-recolonisation" This confirms its role as an opportunistic species, thereby altering the initial community structure on a beach after nourishment. We conclude that the responses of the four dominant invertebrates studied in the years following beach nourishment are species specific. This shows the importance of knowing the autecology of the sandy beach macroinvertebrate fauna in order to be able to mitigate the effects of beach nourishment and other environmental impacts. © 2012 Elsevier Ltd. Source


Janssen J.A.E.B.,Waterboard Rijn and IJssel | Krol M.S.,University of Twente | Schielen R.M.J.,University of Twente | Schielen R.M.J.,Center for Water Management | Hoekstra A.Y.,University of Twente
Environmental Science and Policy | Year: 2010

To support decision making on complex environmental issues, models are often used to explore the potential impacts of different management alternatives on the environmental system. We explored how different model outcomes affect decision making. Two topics have our particular interest, namely (1) the influence of quantification of qualitative information on decision making, and (2) the influence of reflecting uncertainty in the model outcomes on decision making. We set up a survey, in which we use a case study describing a decision making situation in strategic river management. The survey was disseminated through the Internet. From the results we conclude that the quantification of information in itself does not necessarily change preferences, although the outcomes suggest that preferences converge when based on quantified information. When confronted with uncertainty information, respondents show a preference for the alternative with the smallest chance of negative impacts. The study shows that, whereas the modelling community often strives to provide the policy process with as good, and as detailed information as is possible, their assumption that this will automatically lead to 'better' decision making is not self-evident. © 2010 Elsevier Ltd. Source


Stastny J.,Charles University | Kouwets F.A.C.,Center for Water Management
Fottea | Year: 2012

In the present paper, the morphology and taxonomy of seven desmid taxa collected in various European habitats is discussed, mainly on the basis of scanning electron microscopic observations of cell wall sculpturing. Four taxa (Actinotaenium riethii, Closterium pseudocostatum, Cosmarium discrepans and C. hostensiense) are newly described and the name of one taxon (Cosmarium lenzenwegeri) is recombined. In addition, the morphology of Cosmarium cataractarum and C. cinctutum is described in greater detail, confirming their status as independent species. © Czech Phycological Society (2012). Source


Smedes F.,Masaryk University | Smedes F.,Deltares | Van Vliet L.A.,Center for Water Management | Booij K.,Netherlands Institute for Sea Research
Environmental Science and Technology | Year: 2013

The freely dissolved concentration (Cw,0) in the pore water and the accessible (releasable) concentration in the sediment (Cas,0) are important parameters for risk assessment. These parameters were determined by equilibrating contaminated sediments and passive samplers using largely differing sampler-sediment ratios. This method is based on the principle that incubations at low sampler/sediment ratios yield the concentration in the pore water (minor depletion of the sediment phase) and incubations at high sampler/sediment ratios yield the accessible concentration in the sediment (maximum depletion of the sediment phase). It is shown that equilibration was faster in dense suspensions and at high sampler/sediment ratios when compared to low sampler/sediment ratios. An equilibrium distribution model was used to estimate Cw,0 and Cas,0 by nonlinear least-squares regression. The method was evaluated for three sediments (harbor, estuarine, marine). Accessible concentrations of 13 PAHs were 2 (low Kow) to 10 (high Kow) times lower than the total concentrations (three sediments). By contrast, the accessible concentrations of 15 PCBs were about 1.2 times lower than the total concentrations and displayed no trend with K ow (one sediment). Implications for risk assessment and considerations for application of multi-ratio equilibrium passive sampling with other sediments are discussed. © 2012 American Chemical Society. Source

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