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An Automatic Procedure for Dune Foot Position Detection: Application to the Dutch Coast
Coastal indicators are a useful proxy in coastal zone management to describe the status of a physical system and to assess the effectiveness of possible interventions. They can be used as a basis to implement and evaluate coastal erosion policies, as it is done, for example, in The Netherlands. One often used coastal indicator is the position of the dune foot. In the current definition used in The Netherlands to describe the dune foot position, the actual geometry of the profile is, however, not accounted for, but this is simply based on one reference value for the entire coastline. In the present study, an automatic procedure for the detection of the dune foot position is proposed based on the actual shape of the cross-shore profile and on the evaluation of the first and second derivatives of the cross-shore topography. The methodology is compared to visual observations as well as satellite images for case studies in The Netherlands and Portugal, hence showing that the methodology is generally applicable. The algorithm to derive the dune foot position in a cross-shore profile and the database derived from this study are publicly available.
Mapping deep peat carbon stock from a LiDAR based DTM and field measurements, with application to eastern Sumatra
Portable XRF quick-scan mapping for potential toxic elements pollutants in sustainable urban drainage systems : a methodological approach
Sustainable urban drainage systems (SuDS) such as swales are designed to collect, store and infiltrate a large amount of surface runoff water during heavy rainfall. Stormwater is known to transport pollutants, such as particle-bound Potential Toxic Elements (PTE), which are known to often accumulate in the topsoil. A portable XRF instrument (pXRF) is used to provide in situ spatial characterization of soil pollutants, specifically lead (Pb), zink (Zn) and copper (Cu). The method uses pXRF measurements of PTE along profiles with set intervals (1 m) to cover the swale with cross-sections, across the inlet, the deepest point and the outlet. Soil samples are collected, and the In-Situ measurements are verified by the results from laboratory analyses. Stormwater is here shown to be the transporting media for the pollutants, so it is of importance to investigate areas most prone to flooding and infiltration. This quick scan method is time and cost-efficient, easy to execute and the results are comparable to any known (inter)national threshold criteria for polluted soils. The results are of great importance for all stakeholders in cities that are involved in climate adaptation and implementing green infrastructure in urban areas. However, too little is still known about the long-term functioning of the soil-based SuDS facilities.
Innovative water quality and ecology monitoring using underwater unmanned vehicles: field applications, challenges and feedback from water managers
With climate change and urban development, water systems are changing faster than ever. Currently, the ecological status of water systems is still judged based on single point measurements, without taking into account the spatial and temporal variability of water quality and ecology. There is a need for better and more dynamic monitoring methods and technologies. Aquatic drones are becoming accessible and intuitive tools that may have an important role in water management. This paper describes the outcomes, field experiences and feedback gathered from the use of underwater drones equipped with sensors and video cameras in various pilot applications in The Netherlands, in collaboration with local water managers. It was observed that, in many situations, the use of underwater drones allows one to obtain information that would be costly and even impossible to obtain with other methods and provides a unique combination of three-dimensional data and underwater footage/images. From data collected with drones, it was possible to map different areas with contrasting vegetation, to establish connections between fauna/flora species and local water quality conditions, or to observe variations of water quality parameters with water depth. This study identifies opportunities for the application of this technology, discusses their limitations and obstacles, and proposes recommendation guidelines for new technical designs.
De kwaliteit van afstromend hemelwater in Nederland
Ten behoeve van beleidsvorming stelt STOWA samen met stichting RIONED al sinds 2007 een Database Hemelwaterkwaliteit ter beschikking. In 2020 verschijnt een flink herziene versie van deze database. Dit artikel beschrijft de belangrijkste bevindingen op basis van deze nieuwe database.
Assessment of the dynamic properties of holocene peat
The dynamic behavior of a peat deposit in the north of the Netherlands is described. The organic content ranges from 70% to 95%,which is high compared to the organic content generally presented in publications on the dynamic behavior of peats. Shear wave velocities vs and correspondingly small-strain shear moduli G0 closely match values stated in the literature. Correlations stated in the literature for predicting G0 proved to be applicable. Resonant column and cyclic direct simple shear tests were performed to establish the shear modulus reduction curves and damping curves. Excess pore pressure development during testing indicates dilatant behavior. The general trend shows nearly flat shear modulus reduction and damping curves at small strains regardless of organic content. Cyclic direct simple shear tests on humified material showed a larger pore pressure buildup than found in tests on non-to-moderately humified material. Differences in degree of humification did not result in significant differences in the shear modulus reduction curve, including G0 values. Large scatter was found in the damping curves. For the humified material, tested at low stress level, a discontinuity in the damping curve is found at shear strain of 3%, which corresponds to a rapid pore pressure buildup in the tests.
Degradation of polymetallic nodules during hydraulic transport under influence of particle-wall and particle-particle interaction
The mining of polymetallic nodules from the seafloor at depths down to 6000 m requires the excavation of nodules with a seafloor mining tool, the transport of nodules as a slurry through a jumper hose connecting the mining tool to a vertical hydraulic transport system and the transport of the nodules through the vertical lifting pipe. We focus on a concept with conventional hydraulic transport, using a series of centrifugal pump booster stations. The nodules will be transported in different flow regimes, ranging from a sliding bed (in the jumper hose) to a homogeneous suspension (vertical flow). Each regime gives rise to degradation of the nodules in a different way. It is important to understand the degradation mechanisms in detail in order to predict the particle size distribution of the slurry leaving the riser. This particle size distribution is a key design parameter for design of processing equipment and for environmental impact assessment. In this article we present the results of experimental work on abrasive wear (particle-wall interaction) and attrition (particle-particle interaction) of polymetallic nodules from the Clarion Clipperton Zone and we discuss its applicability to engineering practice.
Experimental determination of pressure coefficients for flood loading of walls of Dutch terraced houses
Failure of residential buildings during floods is an important cause of damage and loss of life. In the case of the Netherlands, the collapse of buildings is implicitly included in current damage and mortality curves since these are generated from historical data. However, the Netherlands has not experienced destructive flooding since 1953, so damage functions for modern buildings do not exist. Therefore, this paper assesses the effect of floods on modern Dutch residences with laboratory tests and structural models in order to formulate physically-based fragility curves. The results gathered are also applicable to similarly-built masonry and cavity-wall rowhouses elsewhere.
Recent Change—River Flow
This chapter reviews recent trends and variability in river flows to the North Sea. The main contributors are the River Elbe and the River Rhine. In addition to these large rivers many smaller rivers also discharge into the North Sea. However, by far the biggest contributor is the Baltic Sea outflow. Observation records for the major rivers draining into the North Sea are relatively long, while records for the smaller rivers are typically much shorter. Variability in flow is dependent on variations in weather—mainly precipitation and temperature—from year to year, but also on a wide range of direct and indirect human interventions in the North Sea basin. Rivers draining into the North Sea show considerable interannual and decadal variability in annual discharge. In northern areas this is closely associated with variation in the North Atlantic Oscillation, particularly in winter. Discharge to the North Sea in winter appears to be increasing, but there is little evidence of a widespread trend in summer inflow. Higher winter temperatures appear to have led to higher winter flows, as winter precipitation increasingly falls as rain rather than snow. To date, no significant trends in response to climate change are apparent for most of the individual rivers discharging into the North Sea.
The Deltares Aqua Monitor
Has the world become wetter or dryer? Can we see global trends in the changes of coastlines, and are these trends also apparent where we live? Is the total surface water storage on land growing or shrinking? These are rather simple questions, but have so far been hard to answer, and yet are important in order to understand the dynamics of our planet and the attribution of these dynamics to climate anomalies, and climate or man-made change. Answering these questions requires the availability of global maps at a very high resolution, which are very accurate and updated frequently. Remotely sensed Earth Observation (EO) data, such as satellite imagery, can obviously be used for this purpose. The volume of such data is increasing exponentially . To store, handle and analyse these data on a global scale requires a combination of access to enormous data storage and highperformance computers. It would require man-years working on the data preparation, exploring algorithms before the actual analysis, could be started. Until recently, such analyses could only be performed by highly specialized scientists and engineers, and on a case-by-case basis. The Deltares Aqua Monitor is a game changer showing that this situation is rapidly changing. It also shows that the way we analyse and use these data differs from what was common practice until very recently.