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Depth-resolving vs depth-averaged modelling of swash zone hydrodynamics
Numerical models have played a big role in gaining new understanding of processes in the swash zone. Until recently, intra-wave sediment transport and morphology has almost exclusively been studied by depth-averaged models and rarely by depth-resolving models. In this paper we highlight some of the important differences between these model types with respect to their application in the swash zone. We compare the depth-resolving OpenFOAM model with the depthaveraged XBeach nonhydrostatic model when applied to a dambreak case. The models reproduce the overall dynamics of the swash event but tend to overpredict the swash depths and velocities. We also find that the depth-resolving model produces large vertical variation in flow velocity. Depth-averaged models cannot reproduce these vertical variabilities. For this reason, the models differ in their treatment of breaking waves. This leads to differences in the uprush, while the backwash flows are more similar. We conclude that depth-resolving models are an important tool to study the swash flows and potentially sediment transport and morphology.
The role of gate operation in reducing problems with cohesive and non-cohesive sediments in irrigation canals
Sediments cause serious problems in irrigation systems, adversely affecting canal performance, driving up maintenance costs and, in extreme cases, threatening system sustainability. Multiple studies were done on the deposition of non-cohesive sediment and implications for canal design, the use of canal operation in handling sedimentation problems is relatively under-studied, particularly for cohesive sediments. In this manuscript, several scenarios regarding weirs and gate operation were tested, using the Delft3D model, applied to a case study from the Gezira scheme in Sudan. Findings show that weirs play a modest role in sedimentation patterns, where their location influences their effectiveness. On the contrary, gate operation plays a significant role in sedimentation patterns. Reduced gate openings may cause canal blockage while intermittently fully opening and closing of gates can reduce sediment deposition in the canal by 54% even under conditions of heavy sediment load. Proper location of weirs and proper adjusting of the branch canal’s gate can substantially reduce sedimentation problems while ensuring sufficient water delivery to crops. The use of 2D/3D models provides useful insights into spatial and temporal patterns of deposition and erosion but has challenges related to running time imposing a rather coarse modelling resolution to keep running times acceptable.
Design verification of Afsluitdijk renovation with large scale tests
In the north of the Netherlands the 32 km long Afsluitdijk divides the Wadden Sea from the Lake IJssel. This dam is being rehabilitated by increasing the crest level to reduce the wave overtopping and reinforce the armour layers on the seaward and lake side of the dam. The Dutch Ministry of infrastructure and Water Management (Rijkswaterstaat division) has commissioned Levvel, a consortium of BAM, Van Oord and Rebel, to carry out this renovation as a design, built, finance and maintenance contract. Rijkswaterstaat gave the opportunity to the contractor to offer an innovative design. New techniques and or armour units were allowed to use, but design verification with large scale physical model tests was prescribed. The verification of the design has been carried out in the Delta Flume of Deltares. Levvel proposed two new armour materials to protect the dam against wave action: Quattroblocks (a product of Holcim Coastal) and Levvel-blocs, internationally known as Xblocplus (by BAM). This paper describes the large-scale tests and results with regard to armour stability and wave overtopping.
Gebiedsgericht grondwaterbeheer in het Rotterdamse Havengebied : toepassing van iMOD-WQ en HydroConnect
De afgelopen jaren heeft Deltares gewerkt aan het mogelijk maken van waterkwaliteitsmodellering en modellering van dichtheidsafhankelijke stroming en transport met iMOD. De code waarmee dit kan heet iMOD-WQ. De eerste toepassing hiervan was ter ondersteuning van de gebiedsgerichte grondwateraanpak (GGA) in het Rotterdamse Havengebied. In dat (nog steeds lopende) project wordt ook gebruik gemaakt van de workflow manager HydroConnect, een andere relatief recente modelleerinnovatie. HydroConnect faciliteert in dit project het gebruik van het ontwikkelde modelinstrument en de uit te voeren "modellentrein" door meerdere partijen. In dit artikel wordt de toepassing van beide innovaties binnen GGA in het Rotterdamse Havengebied toegelicht.
Delta planning: welke scenario's heb je nodig?
Wereldwijd maken beleidsmakers gebruik van scenario’s ter voorbereiding op een onzekere toekomst. De maatschappelijke context verschilt echter van land tot land, en dat maakt dat er ook behoorlijke aanpassingen nodig zijn in de scenariomethodiek. In dit artikel wordt een vergelijking gemaakt van de gebruikte scenario’s van drie deltaplannen, opgesteld in de periode 2009-2017, waarbij Nederlandse adviseurs, waaronder Deltares, betrokken zijn geweest. Het gaat om Nederland, de Mekong Delta in Vietnam en Bangladesh. De veel grotere dynamiek van de ontwikkelingslanden maakt dat sociaaleconomische en ruimtelijke ontwikkelingen op een andere manier in de scenario’s verwerkt moeten worden. Niet behoud, maar ontwikkeling staat voorop, en dat vereist een andere strategie.
Adaptieve planning in de praktijk : strategisch omgaan met de drinkwatervoorziening in Flevoland
De Beleidsnota Drinkwater (Rijksoverheid, 2014) agendeert het belang van een betrouwbare openbare drinkwatervoorziening voor de langere termijn. In 2017/2018 is daarom door de Provincie Flevoland en drinkwaterbedrijf Vitens een toekomstverkenning uitgevoerd naar de drinkwatervoorziening op de lange termijn. Vanwege de onzekerheden in de drinkwatervraag is hierbij gebruik gemaakt van het concept ‘adaptieve planning’ (Van der Brugge en Vermooten, 2018). Deze aanpak stelt de Provincie Flevoland en Vitens in staat om steeds opnieuw te bekijken of het aanbod van drinkwater voldoende blijft onder verschillende drinkwatervraagscenario’s en welke maatregelen eventueel genomen kunnen worden. In dit artikel wordt beschreven hoe de Provincie Flevoland en Vitens de methode van adaptieve planning toepassen in de drinkwatersector. Hiertoe zal eerst kort worden ingegaan op de drinkwatersituatie in Flevoland. Vervolgens zal worden beschreven hoe de methode van adaptieve planning is toegepast en hoe de Provincie Flevoland en Vitens het in de praktijk uitvoeren.
Impacts on infrastructure, built environment, and transport
This document will assess climate risks due to increased coastal and river flooding for the infrastructure, built environment, and the transport sector according to the protocol defined in D1.6 using the scenarios defined in D1.5. of the COACCH project. The assessment uses state-of-the art models for coastal and river flooding as well as a new model for flood impacts to transport networks and computer impacts for Europe at higher spatial resolution (NUTS2) compared to previous studies. The assessment includes the impacts of gradual land loss due to submergence and erosion as well as the impact of increased damage to coastal built environment provoked by extreme sea-level events.
Systemic flood risk management : the challenge of accounting for hydraulic interactions
Rivers typically flow through multiple flood-protected areas which are clearly interconnected, as risk reduction measures taken at one area, e.g. heightening dikes or building flood storage areas, affect risk elsewhere. We call these interconnections ‘hydraulic interactions’. The current approach to flood risk management, however, neglects hydraulic interactions for two reasons: They are uncertain and, furthermore, considering them would require the design of policies not only striving for risk reduction, but also accounting for risk transfers across flood-protected areas. In the present paper, we compare the performance of policies identified according to the current approach with those of two alternative formulations: One acknowledging hydraulic interactions and the other also including an additional decision criterion to account for equity in risk distribution across flood-protected areas. Optimal policies are first identified under deterministic hydraulic interactions, and, next, they are stress-tested under uncertainty. We found that the current approach leads to a false sense of equal risk distribution. It does, however, perform efficiently when a risk-averse approach towards uncertain hydraulic interactions is taken. Accounting for hydraulic interactions in the design of policies, instead, increases efficiency and both efficiency and equity when hydraulic interactions are considered deterministically and as uncertain, respectively.
How do climate risks affect corporations and how could they address these risks?
Physical and transitional risks resulting from climate change are already inducing significant direct and indirect impacts on organizations—such as damages to assets, disruption to supply chains, or shifts in supply and demand for certain commodities, products or services. The current short-termism of most companies suggests the importance of raising awareness among the private sector about the potential risks of climate change. However, companies increasingly are reporting and disclosing climate risks and associated costs as asked for benchmarking by financial institutions and to comply with regulations with respect to sustainable finance. A guidance on how to do a climate risk assessment and to estimate the costs of physical climate risk as well as transitional and systemic risk concerning their operations and value chain management is lacking. This paper presents a stepwise blueprint on climate risk assessment and financial disclosures that support companies on reorienting capital flows towards more sustainable investments and with their disclosure process to foster transparency and long-termism in financial and economic activity in line with the action plan on sustainable finance adopted by the European Commission in March 2018 to achieve sustainable and inclusive growth.
Material Point Method and applications in geotechnical engineering
A vast number of computational methods is being developed to simulate large deformation problems involving soil-water-structure interaction. Here, the material point method (MPM) is used that was developed to simulate large deformations in history-dependent materials. It combines the advantages of mesh-based and point-based approaches: mesh distortion is eliminated and history is stored in material points. Generally speaking, MPM is an advancement of the finite element method (FEM) where the continuum body is represented by a set of Lagrangian points, so-called material points (MPs). The MPs are moving through an Eulerian background mesh. The MPs carry all physical properties of the continuum such as stresses, strains, density, momentum, material parameters and other state parameters, whereas the background mesh is used to solve the balance equations without storing any permanent information.