Center for Water Management
Center for Water Management
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.
van de Kerkhof M.,VU University Amsterdam |
Groot A.,Wageningen University |
Borgstein M.,Wageningen University |
Bos-Gorter L.,Center for Water Management
Agriculture and Human Values | Year: 2010
Environmental pollution, animal diseases, and food scandals have marked the agricultural sector in the Netherlands and elsewhere in the 1990s. The sector was high on the political and societal agenda and plans were developed to redesign the sector into a more sustainable direction. Generally, monitoring of the agricultural sector is done by means of quantitative indicators to measure social, ecological, and economic performance. To give more attention to the normative character of sustainable development, the Dutch Ministry of Agriculture, Nature, and Food Quality requested for a participatory approach to evaluate Dutch agriculture, which was characterized by stakeholder workshops, dialogue, and learning. This article describes and reflects on this approach, using the Fourth Generation Evaluation framework developed by Guba and Lincoln (Fourth generation evaluation, 1989). Although there are several improvements to be made, the evaluation approach was successful in the way that it gave insight into perceptions, visions, and ambitions of agricultural stakeholders with regard to sustainability. It also encouraged learning about ways to make the agricultural sector more sustainable. And it contributed to the development of a monitoring approach that is complementary to the quantitative, indicator-based, evaluation approach that is generally used and that can be used every few years to see how perceptions and ambitions of stakeholders have developed. © 2009 The Author(s).
ten Brinke W.B.M.,Bureau Blueland |
Kolen B.,HKV Consultants |
Dollee A.,Center for Water management |
van Waveren H.,Center for Water management |
Wouters K.,HKV Consultants
Journal of Contingencies and Crisis Management | Year: 2010
Contingency plans for hazards are based on scenarios at different scales. The most extreme scenarios reflect the idea of 'think the unthinkable'. For large-scale floods in the Netherlands, this idea has been given an upper limit called 'worst credible floods': an upper limit for floods that are still considered realistic or credible by experts. Considering the enormous impact of a worst credible flood in the Netherlands and the uncertainty of how a disaster might unfold, a realistic preparation for flood disasters should leave room for improvisation and should be based on relatively simple plans, and on public awareness. The huge consequences of worst credible floods show that the country's safety will continue to depend on pro-active and preventive measures. © 2010 Blackwell Publishing Ltd.
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.
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.
Booij P.,VU University Amsterdam |
Sjollema S.B.,University of Amsterdam |
Leonards P.E.G.,VU University Amsterdam |
de Voogt P.,University of Amsterdam |
And 5 more authors.
Chemosphere | Year: 2013
The extent to which chemical stressors affect primary producers in estuarine and coastal waters is largely unknown. However, given the large number of legacy pollutants and chemicals of emerging concern present in the environment, this is an important and relevant issue that requires further study. The purpose of our study was to extract and identify compounds which are inhibitors of photosystem II activity in microalgae from estuarine and coastal waters. Field sampling was conducted in the Western Scheldt estuary (Hansweert, The Netherlands). We compared four different commonly used extraction methods: passive sampling with silicone rubber sheets, polar organic integrative samplers (POCIS) and spot water sampling using two different solid phase extraction (SPE) cartridges. Toxic effects of extracts prepared from spot water samples and passive samplers were determined in the Pulse Amplitude Modulation (PAM) fluorometry bioassay. With target chemical analysis using LC-MS and GC-MS, a set of PAHs, PCBs and pesticides was determined in field samples. These compound classes are listed as priority substances for the marine environment by the OSPAR convention. In addition, recovery experiments with both SPE cartridges were performed to evaluate the extraction suitability of these methods. Passive sampling using silicone rubber sheets and POCIS can be applied to determine compounds with different structures and polarities for further identification and determination of toxic pressure on primary producers. The added value of SPE lies in its suitability for quantitative analysis; calibration of passive samplers still needs further investigation for quantification of field concentrations of contaminants. © 2013 Elsevier Ltd.
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.
Warmink J.J.,University of Twente |
Schielen R.M.J.,Center for Water Management
Proceedings of the International Conference on Fluvial Hydraulics, RIVER FLOW 2014 | Year: 2014
The hydraulic roughness of the main channel of most lowland rivers is dominated by bed forms. River bed forms act as roughness to the flow, thereby significantly influencing the water levels, which are essential for flood forecasting. We implemented a time-lag model to predict dynamic bed form evolution during a flood wave. The results showed that the explicit computation of bed form and associated roughness predictions perform equally well as a calibrated model for the Dutch river Rhine branches in the Netherlands. We were able to explain a large part of the roughness of the main channel that is normally calibrated. Using a physically-based roughness prediction improves the accuracy of the modelled water levels for operational flood forecasting. © 2014 Taylor & Francis Group, London.
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).
Labrujere A.L.,Center for Water Management |
Verhagen H.J.,Technical University of Delft
Proceedings of the Coastal Engineering Conference | Year: 2012
When calculating the Carbon Footprint for a product or service, a direct link is made between the total amount of consumed energy and the produced amount of carbon dioxide during production. For that reason calculating the carbon footprint of various alternatives is a very straightforward method to compare energy consumption and more importantly environmental pollution. Applying this method to large hydraulic engineering projects is not being done frequently. In this study the possibilities to apply the Carbon Footprint method to coastal protection systems have been explored and analyzed. The analyses are based on a case study: A reinforcement work at the Dutch coast.