4266 resultaten

  • A systematic design approach for objectifying Building with Nature solutions

    Auteurs: Vries, M.B. de; Koningsveld, M. van; Aarninkhof, S.G.J.; Vriend, H.J. de (2021)

    Although nature-based design philosophies, such as BwN, have found broad support, a key issue that inhibits a wider mainstream implementation is the lack of a method to objectify BwN concepts. With objectifying, we mean turning the implicit into an explicit engineerable ‘object’, on the one hand, and specifying clear design ‘objectives’, on the other. This paper proposes the “Frame of Reference” approach as a method to systematically transform BwN concepts into functionally specified engineering designs. It aids the rationalisation of BwN concepts and facilitates the transfer of crucial information between project development phases, which benefits the uptake, acceptance and eventually the successful realisation of BwN solutions. It includes an iterative approach that is well suited for assessing status changes of naturally dynamic living building blocks of BwN solutions. The applicability of the approach is shown for a case that has been realised in the Netherlands. Although the example is Dutch, the method, as such, is generically applicable.

  • A rheological and microstructural study of two-step yielding in mud samples from a port area

    Auteurs: Shakeel, A.; MacIver, M.R.; Kan, P.J.M. van; Kirichek, A.; Chassange, C. (2021)

    Natural fine-grained suspensions usually exhibit a complex rheological fingerprint -in particular a two-step yielding phenomenon- due to the presence of mineral clay particles and organic matter (often found in a flocculated state). These rheological properties may vary considerably from one location to another due to the differences in mud composition (specifically in organic matter content). In this study, the origin of this two-step yielding behaviour for natural suspensions is discussed with the help of different experimental techniques including rheology, particle sizing, rheo-optics, and video microscopy. The samples were collected from different locations in the Port of Hamburg, Germany. A rheological analysis of the samples was performed with amplitude sweep, frequency sweep, stress ramp-up and structural recovery tests. The shear-induced structural changes of mud samples was studied by using a parallel plate shearing device with a microscope. Mineral clay-organic matter flocs were studied using video microscopy to obtain the floc size, floc density and settling velocity of flocs. Higher values of rheological properties such as cross-over stress, yield stress, and moduli were observed for samples having higher organic matter content. These samples also produced the largest floc sizes. The rheo-optical analysis showed the formation of cylinder-like structures in fine-grained suspensions upon shearing action, which reflect the origin of two-step yielding behaviour in mud samples, observed in stress ramp-up and amplitude sweep tests.

  • Integrating intensity and context for improved supervised river ice classification from dual-pol Sentinel-1 SAR data

    Auteurs: Roda Husman, S. de; Sanden, J.J. van der; Lhermitte, S.L.M.; Eleveld, M.A. (2021)

    River ice is a major contributor to flood risk in cold regions due to the physical impediment of flow caused by ice jamming. Although a variety of classifiers have been developed to distinguish ice types using HH or VV intensity of SAR data, mostly based on data from RADARSAT-1 and -2, these classifiers still experience problems with breakup classification, because meltwater development causes overlap in co-polarization backscatter intensities of open water and sheet ice pixels. In this study, we develop a Random Forest classifier based on multiple features of Sentinel-1 data for three main classes generally present during breakup: rubble ice, sheet ice and open water, in a case study over the Athabasca River in Canada. For each ice stage, intensity of the VV and VH backscatter, pseudo-polarimetric decomposition parameters and Grey Level Co-occurrence Matrix texture features were computed for 70 verified sample areas. Several classifiers were developed, based on i) solely intensity features or on ii) a combination of intensity, pseudo-polarimetric and texture features and each classifier was evaluated based on Recursive Feature Elimination with Cross-Validation and pair-wise correlation of the studied features. Results show improved classifier performance when including GLCM mean of VV intensity, and VH intensity features instead of the conventional classifier based solely on intensity. This highlights the complementary nature of texture and intensity for the classification of breaking river ice. GLCM mean incorporates spatial patterns of the co-polarized intensity and sensitivity to context, while VH intensity introduces cross-polarized surface and volume scattering signals and is less sensitive to wind than the commonly used co-polarized intensity. We conclude that the proposed method based on the combination of texture and intensity features is suitable for and performs well in physically complex situations such as breakup, which are hard to classify otherwise. This method has a high potential for classifying river ice operationally, also for data from other SAR missions. Since it is a generic approach, it also has potential to classify river ice along other rivers globally.

  • Viscoplastic cyclic degradation model for soft natural soils

    Auteurs: Zuada Coelho, B.E.; Dijkstra, J.; Karstunen, M. (2021)
    Gepubliceerd in: Computers and geotechnics, volume 135 (2021), pagina 1-12

    Cyclic loading affects the long-term response of geostructures build on natural soils. Soft soils are particularly susceptible to the development of large deformations, induced by the repetitive nature of loading. A new viscoplastic cyclic accumulation model is presented, which is an hierarchical extension of the Creep-SClay1S model, to model the long-term permanent deformation resulting from undrained cyclic loading of natural soft clays. The cyclic cumulative strains are incorporated by means of an additional viscoplastic multiplier. This cyclic viscoplastic multiplier adds four additional model parameters that are derived from undrained cyclic triaxial tests. The model is calibrated using experimental data from undrained cyclic triaxial tests performed on high quality block samples of natural Onsøy clay, at different average shear stresses, shear stress amplitudes and loading periods. The accuracy of the proposed model is demonstrated by comparing the element level simulations with the experimental data. The applicability of the proposed model is further illustrated with a boundary value problem, where an embankment submitted to cyclic loading is simulated. The use of the new model enables the simulation of the response of cyclic loaded foundations on soft soils, where the serviceability limit state over a long period of time is governing the design.

  • High biodiversity in a benzene-degrading nitrate-reducing culture is sustained by a few primary consumers

    Auteurs: Melkonian, C.; Waals, M.J. van der; Gerritse, J. (2021)

    A key question in microbial ecology is what the driving forces behind the persistence of large biodiversity in natural environments are. We studied a microbial community with more than 100 different types of species which evolved in a 15-years old bioreactor with benzene as the main carbon and energy source and nitrate as the electron acceptor. Using genome-centric metagenomics plus metatranscriptomics, we demonstrate that most of the community members likely feed on metabolic left-overs or on necromass while only a few of them, from families Rhodocyclaceae and Peptococcaceae, are candidates to degrade benzene. We verify with an additional succession experiment using metabolomics and metabarcoding that these few community members are the actual drivers of benzene degradation. As such, we hypothesize that high species richness is maintained and the complexity of a natural community is stabilized in a controlled environment by the interdependencies between the few benzene degraders and the rest of the community members, ultimately resulting in a food web with different trophic levels.

  • A novel coastal landscape model for sandy systems : community base for interdisciplinary research on coastal evolution

    Auteur: Luijendijk, A.P. (2021)

    A common measure to mitigate erosion along sandy beaches is the implementation of sand nourishments. The design and societal acceptance of such a soft mitigation measure demands information on the expected evolution at various time scales ranging from a storm event to multiple decades. Process-based morphodynamic models are increasingly applied to obtain detailed information on temporal behaviour. This paper discusses the process-based morphodynamic model applied to the Sand Motor and how the morphodynamic forecasts have benefitted from the findings of an interdisciplinary research program called NatureCoast. The starting point is the morphodynamic prediction of the Sand Motor made for an Environmental Impact Assessment in 2008 before construction began. After the construction, the model computations were optimized using the first-year field measurements and insights by applying advanced model features. Next, an integrated model was developed that seamlessly predicts the morphodynamics in both the subaqueous and subaerial domains of the Sand Motor. Decadal predictions illustrate the need to be able to resolve the marine and aeolian processes simultaneously in one modelling framework in the case of dynamic coastal landscapes. Finally, a novel morphodynamic acceleration technique was developed that allows for predicting the morphodynamics for multiple decades while incorporating storm events in one simulation. Combining the above-mentioned developments has led to a unique, open-source, process-based landscape tool for (complex) coastal sandy systems, which can stimulate further collaboration between research communities. Moreover, this work demonstrates the evolution from mono- to interdisciplinary forecasts of coastal evolution.

  • The lifecycle of public value creation : eroding public values in the Dutch Marker Wadden project

    Auteurs: Willems, J.J.; Duijn, M.; IJff, S.; Veraart, J.A.; Nuesink, N.; Ellen, G.J.; Buuren, A. van (2021)

    This paper examines the durability of public value coalitions in the Dutch Marker Wadden project: an internationally acclaimed water project. The paper compares public value creation by coalitions before and after project appraisal. Activities before project appraisal mainly worked towards the integration of values and interests, while activities after project appraisal facilitated disintegration. The findings underscore the difficulty of delivering a broad conception of public value, potentially leading to a hollowed-out result compared to the original interpretation. Parties involved in public–private partnerships (PPPs) should be aware of the lifecycle of public value creation. The broad conception of public value as defined in the early stages, which is needed to ensure co-financing, often disappears during the implementation, as projects become bound to tight frameworks. Coalition building focuses more on securing project approval than on ensuring a full representation of values in the implementation stage. This dynamic can result in unsatisfied partners. Parties should therefore build in more checks and balances to prevent opportunistic behaviour.

  • Vispasseerbaarheid stuwcomplexen : kennisvragen beantwoorden en analysetool ontwikkelen

    Auteurs: Ruijgh, E.F.W.; Jong, J.S. de; Kramer, N.L. (2021)

    Vismigratie vormt een belangrijk aspect van het functioneren van het ecosysteem in het hoofdwatersysteem van Rijkswaterstaat. Slechte passeerbaarheid voor vis van barrières zoals stuwcomplexen is een risico voor het in stand houden van vispopulaties. Het passeerbaar maken van deze barrières, en daarmee het herstel van de longitudinale connectiviteit in de rivieren, speelt een sleutelrol in het herstel van de populaties van migrerende vissoorten.In de literatuur is allerlei informatie beschikbaar over de bijdrage van de verschillende verliesposten bij de stuwcomplexen – zowel in stroomopwaartse als in stroomafwaartse richting – voor verschillende vissoorten/gildes. Veel van deze informatie is gebaseerd op meetgegevens bij een specifiek object, voor een specifieke soort, op een bepaald moment, onder bepaalde omstandigheden. De bijlages van dit rapport geven een overzicht van deze informatie.

  • Performance of full scale constructed wetlands in removing antibiotics and antibiotic resistance genes

    Auteurs: Sabri, N.A.; Schmitt, H.; Zaan, B.M. van der; Gerritsen, H.W.; Rijnaarts, H.H.M.; Langenhoff, A.A.M. (2021)
    Gepubliceerd in: Science of the total environment (2021), pagina 1-42

    Additional treatment of wastewater, such as constructed wetlands (CWs), is a possible solution to reduce the discharge of antibiotics and antibiotic resistance genes (ARGs) from households and industry to the environment. This study aims to investigate the occurrence and removal of antibiotics and ARGs by two full scale CWs operated at different hydraulic retention times (HRT), namely 1 day and 3 days. Both CWs were receiving the same wastewater treatment plant (WWTP) effluent. Temporally and spatially distributed sampling of water and sediment was conducted for one year and samples were analyzed for antibiotics and ARGs by using LC-MS/MS and qPCR. Results showed that both CWs removed antibiotics significantly with a comparable overall removal of 28% - 100%, depending on the type of antibiotics. However, some of the antibiotics showed higher concentration after the CW treatment. Five antibiotics (tiamulin, tylosin, oxytetracycline, sulfamethoxazole and trimethoprim) were the most abundant (>1500 ng/L on average) in winter. Meanwhile, ermB was the most abundant (average of 5.0 log) in winter compared to summer (average of 3.5 log). Other ARGs did not show a significant increase or decrease between winter and summer. ARGs were removed from the wastewater by 0.8 to 1.5 log. The HRT did not influence the removal of either the antibiotics or the ARGs. A strong correlation was found between sul genes and intI1. The results also revealed a positive and a negative relationship from sampling point 1 to sampling point 5: a positive relation between abundance of antibiotics, ARGs, and of NO3–N, NH4–N, TP, COD and a negative relation between antibiotics, ARGs and temperature. This relationship showed the effect between antibiotics and ARGs concentrations with physicochemical parameters and nutrients. The ability of CWs to reduce the input of micropollutants into the environment makes CWs a potential post treatment to WWTP.

23Page 4 of Array456