3767 resultaten

  • An assessment of measured and computed depth of closure around Japan

    Auteurs: Udo, K.; Ranasinghe, R.; Takeda, Y. (2020)
    Gepubliceerd in: Scientific reports : an open-access multidisciplinary journal, volume 10 (2020), pagina 1-8

    A priori knowledge of the so called depth of closure (DoC) is a pre-requisite to understand and model coastal morphological response to wave forcing, which in turn enables the design of appropriate coastal adaption/protection measures. In the absence of long term measurements of coastal profile data, the DoC is often computed using Hallermeier’s formulations or derivatives thereof, for applications around the world. However, there are two major unresolved issues associated with computing the DoC in this way: the accuracy of the wave data required for reliable DoC computations, and the generic applicability of the coefficients used in DoC equations. This study exploits the availability of DoCs derived from multiple measurements of coastal profiles and wave data along the Japanese coast together with wave reanalysis products to evaluate the validity of DoC calculation approaches. Results show that the accuracy of computed DoC values determined using wave reanalysis data is limited, particularly when the spatial resolution of the wave reanalysis data is lower. Furthermore, coefficients of DoC equations proposed in previous and present studies appear to be location specific and points toward the need for a concerted worldwide meta-analysis that compares observed and derived DoC in order to derive a globally applicable formulation for DoC computations.

  • Using in situ density and strength measurements for sediment maintenance in ports and waterways

    Auteurs: Kirichek, A.; Shakeel, A.; Chassagne, C. (2020)
    Gepubliceerd in: Journal of soils and sediments (2020), pagina 1-7

    Fluid mud layers can be substantial in waterways and they can jeopardise navigation when the ship’s keel comes in its vicinity. The nautical bottom has therefore to be properly characterised. Mud density and yield stress are usd as criteria to characterise the nautical bottom. For a decade, measuring these parameters in situ has been a challenging task. The goal of this paper is to compare the parameters obtained from recently developed in situ measuring instruments. Our results show that the correlation between density and yield stress measurements, as a function of different measuring equipment, strongly depends on the type of mud. Therefore, a proper calibration should be performed by establishing a reference database for each equipment. In order to decrease the amount of in situ survey, it is also necessary to develop models that can accurately predict the consolidation over time.

  • Monitoring underwater nourishments using multibeam bathymetric and backscatter time series

    Auteurs: Gaida, T.C.; Dijk, T.A.G.P. van; Snellen, M.; Vermaas, T.; Mesdag, C.S.; Simons, D.G. (2020)
    Gepubliceerd in: Coastal engineering : an international journal for coastal, harbour and offshore engineers, volume 158 (2020), pagina 1-16

    Natural and man-induced coastal erosion endanger life and environment in coastal areas worldwide. For sedimentary barrier coasts, beach and underwater nourishments are an efficient coastal protection strategy. To optimize nourishments and to understand their impact on the marine environment, monitoring strategies are required. In this study, we investigate the potential of multibeam echosounder (MBES) data, providing both bathymetry and backscatter (BS), for monitoring the evolution of the nourished sediment and morphodynamics over time. A time series of seven MBES measurements, as well as two sets of box cores, vibrocores and seismic data were acquired of a channel-side nourishment near the Wadden Sea island Ameland (The Netherlands), between April 2017 and May 2019. In general, a high confidence of the acoustic reliability of the BS time series measurements is demonstrated. The unsupervised Bayesian classification method, supported by ground-truthing, is employed to produce a time series of sediment maps, revealing sediments ranging from sandy mud to sand with varying amounts of shell fragments. Based on the sediment maps, the nourished sediment could be distinguished from the natural sediment. Within one year, the shell-rich pre-nourishment seabed is recreated by washing out finer sediments, which are deposited towards the main tidal channel. Using the seismic data and vibrocores, the shell-rich pre-nourishment seabed could be identified in the subsurface after being buried by the nourishments, supporting the general findings. Furthermore, a rapid development of steep bedforms with increasing sediment sorting is observed in parts of the nourished areas. This study shows that high-resolution sediment maps obtained from a time series of MBES BS together with bathymetry reveal morphodynamic and sedimentary processes of nourishment evolution and can advance underwater nourishment strategies.

  • Mind the gap : towards a typology of climate service usability gaps

    Auteurs: Raaphorst, K.; Koers, G.; Ellen, G.J.; Oen, A.; Kalsnes, B.; Well, L. van; Koerth, J.; Brugge, R. van der (2020)
    Gepubliceerd in: Sustainability, volume 12 (2020) nummer 4, pagina 1-21

    Literature on climate services presents a large diversity of different services and uses. Many climate services have ‘usability gaps’: the information provided, or the way it is visualized, may be unsuitable for end users to inform decision-making processes in relation to adaptation against climate change impacts or for the development of policies to this end. The aim of this article is to contribute to more informed and effcient decision-making processes in climate adaptation by developing a typology of usability gaps for climate services. To do so, we first present and demonstrate a so-called ‘climate information design’ (CID) template with which to study and potentially improve the visual communicative qualities of climate services. Then, two climates services are selected for a further, qualitative explorative case study of two cases in the north and south of the Netherlands. A combination of focus group sessions and semi-structured interviews are used to collect data from Dutch governmental stakeholders as well as private stakeholders and NGOs. This data is then coded to discover what usability gaps are present. We then present twelve different types of usability gaps that were encountered as a typology. This typology could be used to improve and redesign climate services.

  • Meetnet Nutriënten Landbouw Specifiek Oppervlaktewater : toestand en trends tot en met 2018

    Auteurs: Buijs, S.; Ouwerkerk, K.; Rozemeijer, J.C. (2020)

    In dit onderhavige onderzoek is het MNLSO geactualiseerd en zijn nieuwe toestand- en trendanalyses uitgevoerd voor de periode tot en met 2018. Uit de toestand-analyse komt naar voren dat de waterkwaliteit in de landbouw specifieke wateren verbetert, maar dat er in de periode 2015 tot en met 2018 voor N-totaal op 46 tot 64% van de meetlocaties nog niet aan de waterschapsnorm voor N-totaal wordt voldaan. Voor P-totaal voldoet 45 tot 64% niet in deze periode.

  • Modelstudie Effecten Slibpluim Zandkreek

    Auteurs: Duren, L.A. van; Cado van der Lelij, J.A.; Hanssen, J.; Gaytan Aguilar, S.; Kessel, T. van (2019)

    Rijkswaterstaat (RWS) heeft het voornemen om scheepvaart tussen de Oosterschelde en het Veerse Meer in de Oosterschelde te faciliteren door de Zandkreek uit te baggeren. Bagger- en stort werkzaamheden leiden tot (re)suspensie van het zand-slib mengsel en vertroebeling van het water. Dit heeft gevolgen voor de ecologie en gebruiksfuncties in de omgeving. Deltares is gevraagd om de potentiële negatieve effecten in kaart te brengen. Dit gebeurt door een modelstudie uit te voeren met een aantal verspreidingsscenario's. Bij elk scenario is gekeken naar verandering van slib op de bodem en in de waterkolom. Zodoende kan worden bepaald welke scenarios het minste effect hebben op de verschillende natuur- en gebruikersfuncties. De gegevens van deze analyse worden gebruikt voor het uitvoeren van een passende beoordeling.

  • A vision for hydrological prediction

    Auteurs: Lavers, D.A.; Ramos, M.H.; Magnussen, L.; Pechlivanidis, I.; Klein, B.; Prudhomme, C.; Arnal, L.; Crochemore, L.; Hurk, B. van den; Weerts, A.H.; Harrigan, S.; Cloke, H.L.; Richardson, D.S.; Pappenberger, F. (2020)
    Gepubliceerd in: Atmosphere, volume 11 (2020) nummer 3, pagina 1-12

    IMproving PRedictions and management of hydrological EXtremes (IMPREX) was a European Union Horizon 2020 project that ran from September 2015 to September 2019. IMPREX aimed to improve society’s ability to anticipate and respond to future extreme hydrological events in Europe across a variety of uses in the water-related sectors (flood forecasting, drought risk assessment, agriculture, navigation, hydropower and water supply utilities). Through the engagement with stakeholders and continuous feedback between model outputs and water applications, progress was achieved in better understanding the way hydrological predictions can be useful to (and operationally incorporated into) problem-solving in the water sector. The work and discussions carried out during the project nurtured further reflections toward a common vision for hydrological prediction. In this article, we summarized the main findings of the IMPREX project within a broader overview of hydrological prediction, providing a vision for improving such predictions. In so doing, we first presented a synopsis of hydrological and weather forecasting, with a focus on medium-range to seasonal scales of prediction for increased preparedness. Second, the lessons learned from IMPREX were discussed. The key findings were the gaps highlighted in the global observing system of the hydrological cycle, the degree of accuracy of hydrological models and the techniques of post-processing to correct biases, the origin of seasonal hydrological skill in Europe and user requirements of hydrometeorological forecasts to ensure their appropriate use in decision-making models and practices. Last, a vision for how to improve these forecast systems/products in the future was expounded, including advancing numerical weather and hydrological models, improved earth monitoring and more frequent interaction between forecasters and users to tailor the forecasts to applications. We conclude that if these improvements can be implemented in the coming years, earth system and hydrological modelling will become more skillful, thus leading to socioeconomic benefits for the citizens of Europe and beyond.

  • The Giving Delta : a "systems approach" to a consolidated and sustainable Lower Mississippi River Delta

    Auteurs: Hird, J.; Shelden, J.; Denton, T.; Twilley, R.; Georgiou, I.; Carney, J.; Agre, C.; Sloff, C.J. (2019)
    Gepubliceerd in: Coastal Management 2019 : joining forces to shape our future coasts : proceedings of the 9th ICE conference (La Rochelle, France, 24–26 September 2019) (2020), pagina 1-10

    While generating prosperity for many generations, more than a century of levees-only policy for the training of the Mississippi River to limit riverine flood risk, and river management designed to safeguard navigation, has resulted in massive land loss that threatens communities along the Gulf coast including New Orleans. It has long been recognised that this approach would need to be adjusted, since the consequences of the current strategy, for this and future generations, are increasingly apparent, with the negative impacts increasingly outweighing the positives. To this end, the "Changing Course Design Competition" was established reflecting a growing understanding of the scale and complexity of challenges we will face with increased sea level rise and climate change, both in Deltas and more generally across the globe. This paper outlines the Giving Delta response to the Changing Course Design Challenge, a framework developed by a partnership between US and European private sector, Academic Institutions and Centers of Excellence. Our “design-with nature” approach results in a radical retooling of the management of the Mississippi River and integrated investment strategy as the primary decision drivers. Instead of completely restoring the Mississippi Delta to its natural landscape, a bold, innovative “systems approach” was established in linking the specific needs of the region’s ecosystem, economy and community.

  • Coastal Management 2019 : joining forces to shape our future coasts : proceedings of the 9th ICE conference (La Rochelle, France, 24–26 September 2019)

    Auteurs: Hardiman, N.; Institution of Civil Engineers (2020)

  • Sedimentbalans Waddenzee : synthese ten behoeve van Technisch Advies Kustgenese 2.0

    Auteurs: Elias, E.P.L.; Wang, Z.B. (2020)

    Het zandverlies vanuit het kustfundament naar de Waddenzee is een belangrijke term voor de sedimentbehoefte van het kustfundament. In het kader van het Kustgenese 2.0 onderzoek “lange termijn kustontwikkeling” is de grootte van deze term – in miljoen m3/jaar – onderzocht. Dit syntheserapport heeft tot doel om het verwachte zandverlies naar de Waddenzee en de bandbreedte rondom de verwachting af te leiden voor de periode tot 2035 en voor de periode 2035- 2100. Hiervoor zijn de onderzoeksresultaten van de studies van Elias (2019) en van Wang en Lodder (2019) gebundeld en samengevat.

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