Zoek binnen publicaties
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.
Salt marsh establishment and eco-engineering effects in dynamic estuaries determined by species growth and mortality
Growth conditions and eco‐engineering effects of vegetation on local conditions in coastal environments have been extensively studied. However, interactions between salt marsh settling, growth and mortality as a function of hydro‐morphology and eco‐engineering lack sufficient understanding to forecast morphological development of dynamic systems. We predict salt marsh establishment with an eco‐morphodynamic model that accounts for literature‐based seasonal settling and life‐stage dependent growth and mortality of a generic salt marsh species. The model was coupled to a calibrated hydro‐morphodynamic model of an intertidal bar and, on a coarser grid, to the entire Western Scheldt estuary. To quantify the importance of eco‐engineering effects we compared the dynamic model results to a static model approach. The eco‐morphodynamic model reproduces spatial pattern, cover and growth trends over 15 years. The modelled vegetation cover emerges from the combination of a positive and a new negative eco‐engineering effect: vegetation reduces tidal flow strength facilitating plant survival while the developing salt marsh increases the hydroperiod, which limits large‐scale marsh expansion. The reproduced spatial gradient in vegetation density by our model is strongly correlated to their life‐stages, which underlines the importance of age‐dependence when modeling vegetation and for predictions of the stability of the marsh. Upscaling of the model to the entire estuary on a coarser grid gives implications for grid‐size dependent modeling of hydrodynamics and vegetation. In comparison with static model results, the eco‐engineering effects reduce vegetation cover, showing the importance of vegetation dynamics for predictions of salt marsh growth.
Participatory modelling of surface and groundwater to support strategic planning in the Ganga Basin in India
The Ganga Basin in India experiences problems related to water availability, water quality and ecological degradation because of over-abstraction of surface and groundwater, the presence of various hydraulic infrastructure, discharge of untreated sewage water, and other point and non-point source pollution. The basin is experiencing rapid socio-economic development that will increase both the demand for water and pollution load. Climate change adds to the uncertainty and future variability of water availability. To support strategic planning for the Ganga Basin by the Indian Ministry of Water Resources, River Development and Ganga Rejuvenation and the governments of the concerned Indian states, a river basin model was developed that integrates hydrology, geohydrology, water resources management, water quality and ecology. The model was developed with the involvement of key basin stakeholders across central and state governments. No previous models of the Ganga Basin integrate all these aspects, and this is the first time that a participatory approach was applied for the development of a Ganga Basin model. The model was applied to assess the impact of future socio-economic and climate change scenarios and management strategies. The results suggest that the impact of socio-economic development will far exceed the impacts of climate change. To balance the use of surface and groundwater to support sustained economic growth and an ecologically healthy river, it is necessary to combine investments in wastewater treatment and reservoir capacity with interventions that reduce water demand, especially for irrigation, and that increase dry season river flow. An important option for further investigation is the greater use of alluvial aquifers for temporary water storage.
An introduction to the ‘Oceans and Society: Blue Planet’ initiative
We live on a blue planet, and Earth’s waters benefit many sectors of society. The future of our blue planet is increasingly reliant on the services delivered by marine, coastal and inland waters and on the advancement of effective, evidence-based decisions on sustainable development. ‘Oceans and Society: Blue Planet’ is an initiative of the Group on Earth Observations (GEO) that aims to ensure the sustained development and use of ocean and coastal observations for the benefit of society. The initiative works to advance and exploit synergies among the many observational programmes devoted to ocean and coastal waters; to improve engagement with a variety of stakeholders for enhancing the timeliness, quality and range of information delivered; and to raise awareness of the societal benefits of ocean observations at the public and policy levels. This paper summarises the role of the initiative, current activities and considerations for future directions.
Closed-loop model predictive control with mixed-integer optimization of a river reach with weirs
A decision support system for water management based on convex optimization, is applied to a water system containing river branches connected by weirs. This paper describes a convex approximation approach for the model predictive control of weirs implemented using RTC-Tools 2. Model predictive control using RTC-Tools 2 is implemented for a river that contains 12 river reaches divided by controllable weirs and it is tested in closed loop simulation with a non-linear model. By controlling the weir heights, it is shown how the discharge wave is dispatched in the river without the water levels exceeding the bounds.
A review on the durability of PVC sewer pipes : research vs. practice
Polyvinyl chloride (PVC) has become one of the dominant construction materials for sewer systems over the past decades, as a result of its reputed merits. However, since PVC sewer pipes have operated for decades in a hostile environment, concern over their longevity has been lately raised by sewer managers in the Netherlands. Towards that direction, the main factors and mechanisms that affect a PVC pipe’s lifetime are discussed in this article, along with the current lifetime prediction methods and their limitations. The review of relevant case studies indicates that material degradation, if any, occurs slowly. However, inspection (CCTV) data of three Dutch municipalities reveals that severe defects have already surfaced and degradation evolves at an unexpected fast rate. A main reason of this gap between literature and practice is the fact that comprehensive material testing of PVC sewer pipes is rarely found in the literature although it proves to be essential in order to trustfully assess the level of degradation and its origins.
An overview of continuation methods for non-linear model predictive control of water systems
This paper presents a new class of optimization algorithms for nonlinear hydraulic models of water systems, the so-called continuation methods. Solution stability is singled out as an necessary condition for real-life deployment of nonlinear model predictive control of water systems. The paper discusses the stability of solutions produced by traditional approaches and presents improvements of the continuation method. The method has been implemented into the software package RTC-Tools. The application of the continuation method is illustrated with the help of a case study: an operational system for the drainage of a lowland region (polder) in the Western Netherlands.
On the genesis of new ridges at prograding coasts
Prograding coasts usually feature the occurrence of multiple beach and/or foredune ridges whose record has been widely recognized to provide relevant information about changing meteocean conditions, sediment supply or sealevel oscillations. Yet, their formation, process of individualization and the mechanisms that determine their final configuration remain vague and under discussion. Progradation rate is the most commonly accepted factor regulating the final configuration and number of ridges while other factors as wind strength has been traditionally disregarded in this process. Here, we investigate the formation of multiple ridges across a prograding profile with relation to variable progradation rates and wind strength. For that, we use a process-based approach that integrates marine and aeolian processes by coupling XBeach and Duna models. Twenty-year simulations show successful generation of new ridges, whose number and shape appears modulated by the magnitude of the progradation rate and to a lesser degree by wind strength. Yet, simulations also suggest that marine processes are key on the process of dune ridge individualization, allowing or preventing the formation of a stable backshore or platform.
X Jornadas de Geomorfología Litoral : libro de ponencias (Castelldefels, 4-6 de septiembre de 2019)
Benefits and limitations of real options analysis for the practice of river flood risk management
Worldwide, large amounts of money are needed to protect growing populations against increasing flood risks. Decisions on flood risk management measures are often difficult because the future is uncertain, resulting in possible over- or underinvestments. Integrating flexibility or robustness in the decisions are two different ways to deal with this. Real options analysis (ROA) can help to design and evaluate robust and flexible strategies but is hardly used. We examine benefits and limitations by applying ROA to a realistic case study in the Netherlands. We develop robust dike investment strategies and value the flexibility offered by room for the river measures. The ROA for the realistic case study needs a high level of geographical detail, a large number of future scenarios, and the inclusion of stakeholders’ preferences. Limitations are the complexity, the recognition and quantification of uncertainty, and the mapping of possible decisions in time. ROA provides relevant insights for policy makers which can not be reached with standard cost-benefit analysis: first: use high scenarios for the design of measures with high fixed costs (like dikes), and second: the value of flexibility due to room for the river measures increases with uncertainty.