3115 resultaten

  • Plant functional diversity and nutrient availability can improve restoration of floating fens via facilitation, complementarity and selection effects

    Auteurs: Zuidam, J.P. van; Leeuwen, C.H.A. van; Bakker, E.S.; Verhoeven, J.T.A.; IJff, S.; Peeters, E.T.H.M.; Zuidam, B.G. van; Soons, M.B. (2018)
    Gepubliceerd in: Journal of applied ecology (2018), pagina 1-11

    Peat-forming wetlands, particularly floating fens that form the initial stages of these ecosystems, are declining globally due to excavation, dehydration and eutrophication. Restoration typically involves reestablishment of early-successional open-water stages, with oligotrophic conditions that are characteristic for these systems. However, restoration success is notoriously limited. A potential improvement may be to initiate succession by reintroducing of target plant species. Knowledge is therefore needed on (a) which plant functional groups should be reintroduced to stimulate fen formation; and (b) how to manage nutrient levels during restoration, considering that plant growth may be slow in oligotrophic conditions. We hypothesized that increasing functional diversity of introduced species would stimulate the formation of peat-forming target communities, their biomass accumulation and expansion onto open water. We also hypothesized that nutrient availability would mediate the relative contribution of specific functional groups to these effects. We investigated this in 36 artificial outdoor ponds by manipulating plant functional diversity (clonal dominants, clonal stress-tolerators and interstitials) on constructed rafts with fen-forming communities, and subjected these to a range of nutrient loadings over 2 years. Increasing functional diversity as well as increasing nutrient loadings had stimulating effects on plant biomass accumulation, cover formation and rhizome growth onto open water. Both complementarity (due to niche partitioning or facilitation) and selection effects were mechanisms underlying the diversity effect, with a constant relative importance over the entire range of nutrient availabilities. Different functional groups were important for biomass production at different nutrient availabilities. Rhizome formation by clonal stress-tolerators contributed disproportionately to open water colonization, identifying this functional group as key across all nutrient levels.

  • HIC 2018 : proceedings of the 13th International Conference of Hydroinformatics (Palermo, 1-6 July 2018)

  • Short-term control of a storage hydropower under flood risk by multi-stage stochastic optimization

    Auteurs: Uysal, G.; Sensoy, A.; Schwanenberg, D.; Alvarado Montero, R. (2018)
    Gepubliceerd in: HIC 2018 : proceedings of the 13th International Conference of Hydroinformatics (Palermo, 1-6 July 2018) (2018), pagina 1-7

    Operation of water structures especially with conflicting water supply and flood mitigation objectives is under more stress attributed to growing water demand and changing hydro-climatic conditions. Model Predictive Control (MPC) based optimal control solutions has been successfully applied to different water resources applications. In this study, Feedback Control (FBC) and MPC get combined and an improved joint optimization-simulation operating scheme is proposed. Water supply and flood control objectives are fulfilled by incorporating the long term water supply objectives into a time-dependent variable guide curve policy whereas the extreme floods are attenuated by means of short-term optimization based on MPC. A final experiment is carried out to assess the lead time performance and reliability of forecasts in a hindcasting experiment with imperfect, perturbed forecasts. The framework is tested in Yuvacık Dam reservoir where the main water supply reservoir of Kocaeli City in the northwestern part of Turkey (the Marmara region) and it requires a challenging gate operation due to restricted downstream flow conditions.

  • Conference on Big Data from Space (BiDS'17) : research, technology and innovation (28-30 November 2017, Toulouse, France)

  • Fast MI-SAFE platform : foreshore assessment using space technology

    Auteurs: Sala Calero, J.; Hendriksen, G.; Dijkstra, J.; Cado van der Lelij, A.; Vries, M.B. de; Ekkelenkamp, R.; Morris, E.P. (2017)
    Gepubliceerd in: Conference on Big Data from Space (BiDS'17) : research, technology and innovation (28-30 November 2017, Toulouse, France) (2017), pagina 1-4

    Foreshore Assessment using Space Technology (FAST, 2014-2018, EU-FP7 607131) has created a platform for EU Earth Observation (EO) Programme Copernicus services, to support cost-effective, nature-based shoreline protection. Called "MI-SAFE", it is developed with Open Source (OS) Intelligent Geographical Information System (IGIS) components from the OpenEarth stack, and interoperable OGC standards. Processing large volumes of EO data for global coastal vegetation and elevation products is done using the cloud native Google Earth Engine platform. These are intelligently combined with other layers to form the inputs to XBeach, an OS hydrodynamic model developed by Deltares, UNESCO-IHE and TU Delft. Access to data is via a web-based user interface with different resolutions and complexity (Educational and Expert modes), and a Catalogue Service for the Web (CSW). MI-SAFE is intended to be a sustainable contribution to coastal Nature-based Solutions, increasing both awareness and facilitating advanced modelling, within the engineering community.

  • Tools and methods in participatory modeling : selecting the right tool for the job

    Auteurs: Voinov, A.; Basco Carrera, L. (2018)
    Gepubliceerd in: Environmental modelling and software (2018), pagina 1-47

    Various tools and methods are used in participatory modelling, at different stages of the process and for different purposes. The diversity of tools and methods can create challenges for stakeholders and modelers when selecting the ones most appropriate for their projects. We offer a systematic overview, assessment, and categorization of methods to assist modelers and stakeholders with their choices and decisions. Most available literature provides little justification or information on the reasons for the use of particular methods or tools in a given study. In most of the cases, it seems that the prior experience and skills of the modelers had a dominant effect on the selection of the methods used. While we have not found any real evidence of this approach being wrong, we do think that putting more thought into the method selection process and choosing the most appropriate method for the project can produce better results. Based on expert opinion and a survey of modelers engaged in participatory processes, we offer practical guidelines to improve decisions about method selection at different stages of the participatory.

  • Characterizing export of land-based microplastics to the estuary - Part II : Sensitivity analysis of an integrated geospatial microplastic transport modeling assessment of tire and road wear particles

    Auteurs: Unice, K.M.; Weeber, M.P.; Abramson, M.M.; Reid, R.C.D.; Gils, J.A.G. van; Markus, A.A.; Vethaak, A.D.; Panko, J.M. (2018)
    Gepubliceerd in: Science of the total environment (2018), pagina 1-35

    Integrated models addressing microplastic (MP) generation, terrestrial distribution, and freshwater transport are useful tools characterizing the export of MP to marine waters. In Part I of this study, a baseline watershed-scale MP mass balance model was developed for tire and road wear particles (TRWP) in the Seine watershed. In Part II, uncertainty and sensitivity analysis (SA) methods were used to identify the parameters that determine the transport of these particles to the estuary. Local differential, local range and global first-order variance-based SA identified similar key parameters. The global SA (1000 Monte Carlo simulations) indicated that most of the variance in TRWP exported to the estuary can be apportioned to TRWP diameter (76%), TRWP density (5.6%), the fraction of TRWP directed to combined sewers with treatment (3.9%), and the fraction of TRWP distributed to runoff (versus roadside soil; 2.2%). The export fraction was relatively insensitive to heteroaggregation processes and the rainfall intensity threshold for road surface washoff. The fraction of TRWP exported to estuary in the probabilistic assessment was centered on the baseline estimate of 2%. This fraction ranged from 1.4 to 4.9% (central tendency defined as 25th to 75th percentile) and 0.97% to 13% (plausible upper bound defined as 10th to 90th percentiles). This study emphasizes the importance of in situ characterization of TRWP diameter and density, and confirms the baseline mass balance presented in Part I, which indicated an appreciable potential for capture of TRWP in freshwater sediment.

  • Stochastic generation of spatially coherent river discharge peaks for large-scale, event-based flood risk assessment

    Auteurs: Diederen, D.; Liu, Y.; Gouldby, B.; Diermanse, F.L.M.; Vorogushyn, S. (2018)
    Gepubliceerd in: Natural Hazards and Earth System Sciences (2018), pagina 1-18

    Flood risk assessments are required for long-term planning, e.g. for investments in infrastructure and other urban capital. Vorogushyn et al. (2018) call for new methods in large-scale ‘Flood Risk Assessment’ (FRA) to enable the capturing of system interactions and feedbacks. With the increase of computational power, large-scale, continental FRAs have recently become feasible. Flood events cause large damages worldwide. Moreover, widespread flooding can potentially cause large damage in a short time window. Therefore, large-scale (e.g. pan-European) events and for instance maximum probable damages are of interest, in particular for the (re)insurance industry, because they want to know the chance of their widespread portfolio of assets getting affected by large-scale events. Using a pan-European data set of modelled, gridded river discharge data, we tracked discharge waves in all major European river basins. We synthetically generated a large catalogue of synthetic, pan-European events, consisting of spatially coherent discharge peak sets.

  • MPM modelling of static liquefaction in reduced-scale slope

    Auteurs: Ghasemi, P.; Martinelli, M.; Cuomo, S.; Calvello, M. (2018)
    Gepubliceerd in: Numerical Methods in Geotechnical Engineering IX : proceedings of the 9th European Conference on Numerical Methods in Geotechnical Engineering - NUMGE 2018 (June 25-27, 2018, Porto, Portugal) (2018), pagina 1-6

    The paper deals with the capability of Material Point Method (MPM) in simulating retrogressive failure in a case of very loose coarse-grained material. A well documented reduced-scale experimental test taken from literature is used. The case study clearly shows the onset of static liquefaction, a retrogressive failure and rapid flow-like motion with a flat final ground surface. In this paper a single-point MPM formulation is employed to simulate the overall deformation of the slope from the onset of failure, passing through the simulation of static liquefaction, up to the final deposition. To this aim, a hypoplastic constitutive model is used to simulate the liquefiable behaviour of the material. The results of the numerical analyses are in appropriate agreement with the experimental evidence, and also allow some general considerations about the capabilities of using MPM combined with advanced constitutive models to simulate a complex physical process.

  • Users’ perspectives about the potential usefulness of online storylines to communicate river research to a multi-disciplinary audience

    Auteurs: Cortes Arevalo, V.J.; Verbrugge, L.N.H.; Haan, R.J. den; Baart, F.; Voort, M.C. van der; Hulscher, S.J.M.H. (2018)
    Gepubliceerd in: Environmental communication : official journal of the International Environmental Communication Association (2018), pagina 1-17

    Effective communication practices are needed to support adaptive, collaborative and integrative environmental management. We propose the use of online storylines to communicate scientific outcomes in a way that is captivating, easily understood and accessible. Based on 20 interviews, we identified important attributes for the storyline content, structure and user interaction. We designed a storyline example about stakeholders’ perceptions of a river management intervention with consequences on the landscape. The intended audience consists of multi-disciplinary researchers and practitioners that could consider or apply research solutions outside their field of expertise in river management. We introduced the example in a workshop with 14 participants from research and practice. Our findings highlight the importance of including narrative elements via images, interactive figures and timelines to illustrate the research context. Moreover, storylines should explicitly state benefits as well as the limitations of the river research and include a glossary to clarify specific terms.

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