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Beneficial use of dredged sediment to enhance salt marsh development by applying a ‘Mud Motor’
We test an innovative approach to beneficially re-use dredged sediment to enhance salt marsh development. A Mud Motor is a dredged sediment disposal in the form of a semi-continuous source of mud in a shallow tidal channel allowing natural processes to disperse the sediment to nearby mudflats and salt marshes. We describe the various steps in the design of a Mud Motor pilot: numerical simulations with a sediment transport model to explore suitable disposal locations, a tracer experiment to measure the transport fate of disposed mud, assessment of the legal requirements, and detailing the planning and technical feasibility. An extensive monitoring and research programme was designed to measure sediment transport rates and the response of intertidal mudflats and salt marshes to an increased sediment load. Measurements include the sediment transport in the tidal channel and on the shallow mudflats, the vertical accretion of intertidal mudflats and salt marsh, and the salt marsh vegetation cover and composition. In the Mud Motor pilot a total of 470,516m3 of fine grained sediment (D50 of ∼10 μm) was disposed over two winter seasons, with an average of 22 sediment disposals per week of operation. Ship-based measurements revealed a periodic vertical salinity stratification that is inverted compared to a classical estuary and that is working against the asymmetric flood-dominated transport direction. Field measurements on the intertidal mudflats showed that the functioning of the Mud Motor, i.e. the successful increased mud transport toward the salt marsh, is significantly dependent on wind and wave forcing. Accretion measurements showed relatively large changes in surface elevation due to deposition and erosion of layers of watery mud with a thickness of up to 10 cm on a time scale of days. The measurements indicate notably higher sediment dynamics during periods of Mud Motor disposal. The salt marsh demonstrated significant vertical accretion though this has not yet led to horizontal expansion because there was more hydrodynamic stress than foreseen. In carrying out the pilot we learned that the feasibility of a Mud Motor depends on an assessment of additional travel time for the dredger, the effectiveness on salt marsh growth, reduced dredging volumes in a port, and many other practical issues. Our improved understanding on the transport processes in the channel and on the mudflats and salt marsh yields design lessons and guiding principles for future applications of sediment management in salt marsh development that include a Mud Motor approach.
Annual review Deltares 2012
The usability of the sand motor concept
This report describes the usability of the Sand Motor concept for managing the Dutch coast as an alternative to regular sand nourishments. The evaluation of the usability is based on experience with the Sand Motor pilot project before, during and after the construction in 2011 and by making an inventory of the functions and values along the Dutch coast in the present situation and the coming decades.
Annual review Deltares 2011
A framework for sandy strategy development, with a quick scan for (co-)financing potential
The Sand Motor is a partly emerged mega-nourishment at the Delfland coast in the Netherlands. It is an example of a Building with Nature (BwN) solution using natural processes to fulfil multi-functional purposes in coastal management, such as coastal protection, beach recreation and nature development. EcoShape wishes to explore the opportunities for sandy strategies like the sand motor in an international context. To this end, a framework for the development of sandy strategies is developed by a consortium of Deltares, Royal Haskoning DHV and Witteveen+Bos. This framework aims to assist the BwN community to quickly assess whether sandy strategies are feasible and beneficial for projects both in the Netherlands and abroad. The framework consists of five main steps to assess the feasibility of a project. It starts with the context and scope of the project at hand, followed by a system analysis, design and evaluation of strategies and, finally, an assessment of the (co-)financing potential. The framework explicitly accounts for (the capturing of potential) benefits resulting from the strategies from the early stages of the design process in order to increase the potential for (co-)financing for their implementation. This report presents the framework that has been developed, including guidelines and tools for its application in practice.
R&D annual report Deltares 2010
One of the Deltares aims is to make Research and Development results more accessible to the public and the private sector. The R&D Highlights report is one step towards that goal. The chapters of the Highlights report follow the structure of the five social issues that are central to the Deltares mission.
Ecosystem services of the groundwater and the subsurface : filling the knowledge gap
In densely populated areas, the use of groundwater and the subsurface for functions such as groundwater extraction, aquifer thermal energy storage and infrastructure is increasing. This results in a need for subsurface spatial planning and careful consideration of the use of groundwater for several (economic) activities. Since 2013, in the Netherlands special attention is given to ecosystem services (ES) of the groundwater and subsurface in order to assess how human activities make use of ES and influence ES. A technical assessment framework for the sustainable use of the groundwater and subsurface was developed based on the ES concept. In this paper, the goals of the framework are described, followed by the identified eleven ES and the thirty-one human activities influencing the ES and the relations between both. An example of elements in the framework is presented and the practical application of ES in policy is described.
Lessons of past disasters and preparedness actions to cope with future hydrological extreme events in the Netherlands
The Netherlands, being a low-lying delta of the rivers Rhine, Meuse and Scheldt, have grappled for centuries in coping with water-related disasters: floods originating from both storm surges and high river discharges. Projected climate change scenarios learned the country to prepare for even more frequent and more intense extreme events. We realized the need for new solutions: automatically heightening the levees to protect against flooding was no longer a sustainable solution. We had to change the system we worked with for centuries and broaden its goals. The Netherlands revisited their safety standards for protection against flooding, now incorporating a risk-based approach. We introduced nature-based solutions like “Room for the River” to enable higher river discharges and the “Sand Engine” for beach nourishment to complement traditional engineering for protective disaster resilient infrastructure. The Netherlands embraced system thinking to future proof the country, and we incorporated cultural and ecological values into adaptive decision making. The Netherlands has proven it can shift the fundamentals of its strategy to prepare for a changing climate. Essentially, we have addressed the synergies between the agendas of water-related disaster risk reduction and climate adaptation in a coherent way, both of which are essential in reaching the integrated goals of the nation’s long-term vision for sustainable development.
Evaluating a planning support system’s use and effects in urban adaptation : an exploratory case study from Berlin, Germany
Planning Support Systems (PSS) are increasingly used to support collaborative planning workshops in urban adaptation practice. Research has focused on developing such tools and evaluating their use in workshops but has not measured tools’ effects over time on real planning processes, on the participants involved, and on the final outcomes. The role that tools play in adaptation planning, therefore, remains unclear. A longitudinal case study was made to evaluate a PSS, the Adaptation Support Tool (AST), in a design workshop for sustainable urban water management, in Berlin, Germany. The case study also served to test the evaluation framework and generate insights regarding systematic evaluations of tools in planning processes. The case study was carried out over eighteen months, to capture both the details of the workshop and its longer-term effects on the project and participants. Our results show that the AST’s most evident effects were (1) contributory and less tangible in nature (e.g., supporting learning), than directly causal and concrete (e.g., affecting planning decisions), and (2) a function of the process and context in which the workshop took place. This study demonstrates that making systematic, longitudinal evaluations are valuable for studying the role of PSS in urban adaptation planning.
Sinking cities : an integrated approach towards solutions
In many coastal and delta cities land subsidence exceeds absolute sea level rise up to a factor of ten. Without action, parts of Jakarta, Ho Chi Minh City, Bangkok and numerous other coastal cities will sink below sea level. Increased flooding and other widespread impacts of land subsidence result in damage totalling billions of dollars per year. A major cause of severe land subsidence is excessive groundwater extraction due to rapid urbanization and population growth. A major rethink is needed to deal with the ‘hidden’ but urgent threat of subsidence. Deltares presents a comprehensive approach to address land subsidence from the perspective of more sustainable and resilient urban development.