3805 results

  • Eco-engineering decision scaling (EEDS): A new approach to integrating ecosystems within engineered water management systems

    Authors: Matthews, J.H.; Mauroner, A.W.; Grantham, E.; Montecinos, N.E.; Verbist, K.; Jeuken, A.B.M.; Mendoza, G. (2018)

    Eco-Engineering Decision Scaling (EEDS) is an approach that explicitly and quantitatively explores tradeoffs in stakeholder-defined engineering and ecological performance metrics across a range of possible management actions under unknown future hydrological and climate states. The EEDS framework significantly contrasts with approaches typically used to assess the environmental impacts of water infrastructure projects by evaluating tradeoffs in the initial stages of planning and development rather than as a post-hoc “impact” assessment. Such early evaluation of ecosystem vulnerability is needed to reveal a range of potential design and management options in complex social-ecological systems.

  • Advies over de afbouw van de nazorg op de IBC-locaties in Dordrecht : deel 1

    Authors: Hoekstra, N.K.; Weert, J.P.A. de; Waals, M.J. van der (2020)

    Voor acht locaties in Dordrecht waar de bodem is gesaneerd volgens het principe van isoleren, beheersen en controleren (IBC) is onderzocht of de nazorg op verantwoorde wijze kan worden afgebouwd tot een zo laag mogelijk activiteitenniveau. Dat is gebeurd volgens de methode van de “Schijf van Vijf”, die door de werkgroep “Herziene aanpak IBC” van het BodemBreed Forum is ontwikkeld. Hieruit blijkt dat voor twee locaties dit jaar al kan worden overgegaan op volledig passieve nazorg. Op een derde locatie kan dat mogelijk na nader onderzoek, terwijl dit op een vierde locatie na een tijdelijke intensivering van de nazorg, die nu wordt uitgevoerd, wordt voorzien. Voor de overige locaties wordt het inzetten van een significante extensivering van de nazorg binnen vijf jaar mogelijk geacht.

  • A high-resolution global dataset of extreme sea levels, tides, and storm surges, including future projections

    Authors: Muis, S.; Apecechea, M.I.; Dullaart, J.; Lima Rego, J.R. de; Madsen, K.S.; Su, J.; Yan, K.; Verlaan, M. (2020)
    Published in: Frontiers in marine science, volume 7 (2020)

    The world’s coastal areas are increasingly at risk of coastal flooding due to sea-level rise (SLR). We present a novel global dataset of extreme sea levels, the Coastal Dataset for the Evaluation of Climate Impact (CoDEC), which can be used to accurately map the impact of climate change on coastal regions around the world. The third generation Global Tide and Surge Model (GTSM), with a coastal resolution of 2.5 km (1.25 km in Europe), was used to simulate extreme sea levels for the ERA5 climate reanalysis from 1979 to 2017, as well as for future climate scenarios from 2040 to 2100. The validation against observed sea levels demonstrated a good performance, and the annual maxima had a mean bias (MB) of -0.04 m, which is 50% lower than the MB of the previous GTSR dataset. By the end of the century (2071–2100), it is projected that the 1 in 10-year water levels will have increased 0.34 m on average for RCP4.5, while some locations may experience increases of up to 0.5 m. The change in return levels is largely driven by SLR, although at some locations changes in storms surges and interaction with tides amplify the impact of SLR with changes up to 0.2 m. By presenting an application of the CoDEC dataset to the city of Copenhagen, we demonstrate how climate impact indicators derived from simulation can contribute to an understanding of climate impact on a local scale. Moreover, the CoDEC output locations are designed to be used as boundary conditions for regional models, and we envisage that they will be used for dynamic downscaling.

  • The 6M approach to land subsidence

    Authors: Erkens, G.; Stouthamer, E. (2020)

    Though global awareness of land subsidence has increased over recent years, subsidence remains an ongoing and largely unsolved problem, which is exemplified by frequent discoveries of apparently new subsiding areas. This means that for many of these areas there is a continuous and growing need to provide guidance to decision makers on how to tackle this global problem. This paper presents a comprehensive, step-by-step approach to address land subsidence, illustrated by best practise examples from around the world. The approach places emphasis on the long-term sustainability of resources, whose development is related to the subsidence problems. We identified 6 steps, collectively referred to as the 6M approach, that are crucial to tackle subsidence: Measuring, understanding Mechanisms, Modelling, Money, Measures and Monitoring. This paper offers guidance for implementing the 6M approach, and the lessons learned from the real-life examples provide valuable information and inspiration for decision makers and experts to address subsidence. The focus is on subsidence in deltaic and coastal areas where subsidence contributes to relative sea level rise. It is expected that the 6M approach will contribute to lowering the threshold to act on subsidence. The 6M approach is also used as a guiding principle for the thematic subdivision of TISOLS, providing a meaningful linkage between subsidence science and the societal response to subsidence problems.

  • An assessment of present day and future sea level rise at the Dutch coast : Zeespiegelstijging langs de Nederlandse kust en de regionale bestuurlijke consequenties

    Authors: Hurk, B. van den; Geertsema, T.J. (2020)

    In this report an assessment of present day and future sea level rise is given, to provide a scientific background in the related public debates. We start with a discussion on the present-day sea level rise acceleration. Subsequently, we discuss the consistency between sea level rise observations and future sea level projections along the North Sea coast, followed by a discussion on different future sea level projections and their interpretations.

  • Impacts of progressive urban expansion on subsurface temperatures in the city of Amsterdam (The Netherlands)

    Authors: Visser, P.W.; Kooi, H.; Bense, V.; Boerma, E. (2020)
    Published in: Hydrogeology journal : official journal of the International Association of Hydrogeologists (IAH) (2020)

    Subsurface temperatures are substantially higher in urban areas than in surrounding rural environments; the result is a subsurface urban heat island (SUHI). SUHIs and their drivers have received attention in studies world-wide. In this study, a well-constrained data set of subsurface temperatures fromAmsterdam, The Netherlands, is presented. The study demonstrates that, throughmodeling of centuries-long (fromfourteenth to twenty-first century) urban development and climate change, along with the history of both the surface urban heat-island temperatures and ground surface temperatures, it is possible to simulate the development and present state of the Amsterdam SUHI. The results provide insight into the drivers of long-term SUHI development, which makes it possible to distinguish subterranean heat sources of more recent times that are localized drivers (such as geothermal energy systems, sewers, boiler basements, subway stations or district heating) from larger-scale drivers (mainly heat loss from buildings and raised groundsurface temperatures due to pavements). Because these findings have consequences for the assessment of the shallow geothermal potential of the SUHIs, it is proposed to distinguish between (1) a regional, long-term SUHI that has developed over centuries due to the larger-scale drivers, and (2) local anomalies caused by anthropogenic heat sources less than one century old.

  • Wind effects on the water age in a large shallow lake

    Authors: Liu, S.; Ye, Q.; Wu, S.; Stive, M.J.F. (2020)

    As the third largest fresh water lake in China, Taihu Lake is suffering from serious eutrophication, where nutrient loading from tributary and surrounding river networks is one of the main contributors. In this study, water age is used to investigate the impacts of tributary discharge and wind influence on nutrient status in Taihu Lake, quantitatively. On the base of sub-basins of upstream catchments and boundary conditions of the lake, multiple inflow tributaries are categorized into three groups. For each group, the water age has been computed accordingly. A well-calibrated and validated three-dimensional Delft3D model is used to investigate both spatial and temporal heterogeneity of water age. Changes in wind direction lead to changes in both the average value and spatial pattern of water age, while the impact of wind speed differs in each tributary group. Water age decreases with higher inflow discharge from tributaries; however, discharge effects are less significant than that of wind. Wind speed decline, such as that induced by climate change, has negative effects on both internal and external nutrient source release, and results in water quality deterioration. Water age is proved to be an effective indicator of water exchange efficiency, which may help decision-makers to carry out integrated water management at a complex basin scale.

  • Numerical study of bubble screens for mitigating salt intrusion in sea locks

    Authors: Oldeman, A.M.; Kamath, S.; Masterov, M.V.; O'Mahoney, T.S.D.; Heijst. G.J.F. van; Kuipers, J.A.M.; Buist, K.A. (2020)

    In order to mitigate the effects of salt water intrusion at sea locks, bubble screens are installed which act as a barrier between the dense sea water and the fresh water inland. In order to optimize the design of the bubble screen, in this study a state-of-the-art numerical model is developed based on the Euler- Lagrange CFD method which is expanded with a simple salt balance and concentration-density coupling. The model has been validated by means of experimental results on a laboratory-scale bubble screen. The liquid circulation and entrainment have been investigated for two types of bubble injection methods. It is found that the bubble screen is successful as a separator of salt and fresh water in an initial period of τsep = 30 seconds but acts more as a mixer at later times due to the swaying of the screen. The rate of the mixing increases with the air flow rate. Two mechanisms of salt intrusion are distinguished; a delayed density current along the bottom and entrained liquid being circulated through the domain back to the screen. An optimum in air flow rate is found at a Froude air number F r air = 0 . 91 . Bubble screen behaviour is also checked at the lock-scale using lock-scale geometry and simulations. The amount of salt transmitted agrees well with the large-scale field tests up until the reported Fr air numbers but Fr air > > 1 need to be tested to check for the optimum as found in the lab-scale tests.

  • The importance of explicitly modelling sea-swell waves for runup on reef-lined coasts

    Authors: Quataert, E.; Storlazzi, C.D.; Dongeren, A.R. van; McCall, R.T. (2020)
    Published in: Coastal engineering : an international journal for coastal, harbour and offshore engineers (2020)

    The importance of explicitly modelling sea-swell waves for runup was examined using a 2D XBeach short wave-averaged (surfbeat, “XB-SB”) and a wave-resolving (non-hydrostatic, “XB-NH”) model of Roi-Namur Island on Kwajalein Atoll in the Republic of Marshall Islands. Field observations on water levels, wave heights, and wave runup were used to drive and evaluate both models, which were subsequently used to determine the effect of sea-level rise and extreme wave conditions on wave runup and its components. Results show that specifically modelling the sea-swell component (using XB-NH) provides a better approximation of the observed runup than XB-SB (which only models the time-variation of the sea-swell wave height), despite good model performance of both models on reef flat water levels and wave heights. XB-SB has a bias of −0.108 – 0.057 m and scatter index of 0.083–0.639, whereas XB-NH has bias of −0.132 – 0.055 m and 0.122–0.490, respectively. However, both models under-predict runup peaks. The difference between XB-SB and XB-NH increases for more extreme wave events and higher sea levels, as XB-NH resolves individual waves and therefore captures SS-wave motions in runup. However, for even larger forcing conditions with offshore wave heights of 6 m, the island is flooded in both XB-SB and XB-NH computations, regardless the sea-swell wave energy contribution. In such cases XB-SB would be adequate to model flooding depths and extents on the island while requiring 4–5 times less computational effort.

  • Signal test for acoustic fibre optics for the purpose of monitoring varying salinity

    Authors: Kruiver, P.; Obando Hernandez, E.; Pefkos, M. (2020)

    Salt intrusion of surface waters in the Netherlands poses a problem for fresh water resources, for example at intake points of drinking water. Currently, the tools and instruments to monitor and understand salt water intrusions are insufficient. The point sensors of the monitoring network provide valuable information, but only at fixed point locations. RWS is looking for new technology to gather 2D or 3D information about salinity variations in fresh, brackish and salt waterbodies. Two promising techniques are Distributed Acoustic Sensing (DAS) with fibre optic cables and Electrical Resistivity Tomography (ERT). This report describes the results of a laboratory test using DAS.

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