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Deltafact Bomen, bos en waterbeheer
Lokale praktijkvoorbeelden laten zien dat de aanleg van natuurlijk bos, voedselbos en agroforestry in de stroomgebieden van onze wateren van meerwaarde kunnen zijn voor biodiversiteit, koolstofvastlegging, het bufferen van water en waterveiligheid. De Nationale Bossenstrategie, het Klimaatakkoord en het programma Integraal Rivier Management bieden kaders om deze landgebruiksvormen breder toe te passen. De randvoorwaarde is wel dat er verdienmodellen ontwikkeld worden voor de betrokken ondernemers en de ecosysteemdiensten voor de maatschappij worden gekwantificeerd. Op deze vlakken liggen de belangrijkste kennisbehoeften.
30 years of large river restoration : how long do restored floodplain channels remain suitable for targeted rheophilic fishes in the lower river Rhine?
The ecological efficacy of river restoration projects may change over time, resulting in the loss of their ecological function for targeted species. The goal of this study was to evaluate the rheophilic nursery function of restored floodplain channels over time, by analysing 30 years of monitoring data from 12 restoration projects in the lower river Rhine. We hypothesised that the nursery function would change over time, caused by the combined effects of decreasing flow conditions and succession processes affecting habitat heterogeneity. We found that nursery area suitability for rheophilic fish was almost 4 times higher in two-sided connected channels than in one-sided connected channels, although the response trends of rheophilic fish were similar for both water body types. These response curves showed clear optima with channel age, for rheophilic fish abundance at 13 to 14 years post-restoration, indicating optimal nursery conditions. On the other hand, rheophilic species richness showed a steadily decreasing trend with channel age, suggesting aging channels became less suitable as nursery areas for most rheophilic fish species. The presence of permanent flow was found to be the main driving factor in explaining both rheophilic fish community trends and habitat succession in individual restored channels. We did not observe an effect of habitat heterogeneity on nursery function for rheophilic fish. To create and maintain optimal nursery conditions in restored floodplain channels of strongly anthropogenically influenced rivers such as the river Rhine, we propose a management strategy involving cyclic rejuvenation through human intervention, focusing on restoring permanent flow, with a frequency of on average every 15 years, depending on the rate of aggradation and targeted rheophilic species. We also propose a thorough investigation of the relationship between habitat heterogeneity and nursery success in floodplain channels, as a next step in the identification of suitable nursery areas for rheophilic fishes.
The potential of coastal ecosystems to mitigate the impact of sea level rise in shallow tropical bays
Shallow tropical bays in the Caribbean, like Orient Bay and Galion Bay in Saint Martin, are often sheltered by coral reefs. In the relatively calm environment behind the reefs, seagrass meadows grow. Together, these ecosystems provide valuable ecosystem services like coastal protection, biodiversity hotspots, nursery grounds for animals and enhancing tourism and fisheries. However, sea-level rise imperils these ecosystems and the services they provide because of changing hydrodynamic conditions, with potential effects on the interdependencies between these ecosystems. By means of a hydrodynamic model that accounts for the interaction with vegetation (Delft3D Flexible Mesh), the impact of sea-level rise (0.87 m in 2100) is investigated for three scenarios of future reef development (i.e. keep-up, give-up and catch-up). If coral reefs cannot keep up with sea-level rise, the wave height and flow velocity increase significantly within associated bays, with the wave height doubling locally in case of eroding reefs in our model simulations. Since the presence of seagrass strongly depends on the hydrodynamic conditions, the response of seagrass to the future hydrodynamic conditions is projected using a habitat suitability model that is based on a logistic regression. The spatial character of the bays determines the response of seagrass. In Orient Bay, which is deeper and partly exposed to higher waves, the seagrass will likely migrate from the deeper parts to shallow areas that become suitable for seagrass because of the surf zone moving landward. In contrast, the conditions for seagrass worsen in Galion Bay for the catch-up and give-up scenario; due to the shallowness of this bay, the seagrass cannot escape to more suitable areas, resulting in significant seagrass loss. It is shown that healthy coastal ecosystems are able to limit the change in hydrodynamic conditions due to sea-level rise. Therefore, preserving these ecosystems is key for ensuring the resilience of shallow tropical bays to sea-level rise and maintaining their ecosystem services.
Effect of gate selection on the non-cohesive sedimentation in irrigation schemes
In order to cover the crop water requirements, flow control structures such as gates and weirs are used to transfer the desired amount of water from the canals to the field canals. This paper examines the impact of gate operation and the selection of gates on the deposition of non-cohesive sediment. The Delft3D model is used to simulate the effects of different scenarios regarding gate operation and the location of the gate that is opened. The model results showed that the gate selection affects not only hydraulic parameters but also morphological parameters. It was found that opening the gates closer to the offtake resulted in less sediment deposition at the entrance of the branch canal when compared to opening the gates further away. Gate selection can be used as a tool in sediment management. By alternating the opening of different gates sediments that are already deposited after opening one gate can be eroded when another gate is operated, thus minimizing the additional cost of sediment removal. The use of Delft3D proved beneficial as the selection of different gates leads to asymmetric sediment deposition patterns which would be missed when using a 1D model.
Bodemmonster analyse Egmond
Dit rapport beschrijft een lab analyse van nieuwe bodemmonsters bij Egmond die is uitgevoerd ten behoeve van beter inzicht in de hoeveelheid slib in de bodem die beschikbaar is voor resuspensie. Deze informatie zal gebruikt worden voor een verdere kalibratie van het slib-buffermodel voor de Nederlandse kustzone.
Activiteitenplan 2021 Strategisch Onderzoek Deltares
Dit Activiteitenplan 2021 schetst de hoofdlijnen van het Strategisch Onderzoek dat Deltares in 2021 gaat uitvoeren. Eerst presenteren we Deltares en beschrijven de grote maatschappelijke uitdagingen waar Deltares zich op richt. Vervolgens gaan we in op de inhoud van onze vier missiegebieden en geven kerninformatie over onze missiegerichte onderzoeksprogramma’s. De programmering van onze kennisbasis komt aan de orde, en tenslotte een overzicht van de meest actuele financiële kentallen van het Activiteitenplan 2021. In deel 2 zijn de uitgewerkte onderzoeksprogramma’s opgenomen, met meer gedetailleerde informatie over onze programma’s.
Winning suppletiezand voor herstel zwakke schakels Noord-Holland : scenariostudies m.b.t. slibtransport, nutriënttransport en primaire productie voor de periode 2013-2014
In dit rapport is het effect van zandwinning ten behoeve van de versterking van de zwakke schakels Noord-Holland op slibconcentraties, doorzicht, nutrienttransport en primaire productie berekend middels numerieke modellen.
The natural environment in port development: a ‘green handbrake’ or an equal partner?
Rapid urbanization of the coast, growing global trade, stakeholder emancipation and ongoing depletion of natural resources implies that ports can no longer operate and develop without acknowledging and incorporating societal and environmental considerations. Drawing primarily on first-hand experiences in South African ports, supplemented with learning taken from international literature, this paper proposes a conceptual change in the position of the natural environment in port development from that of a ‘green handbrake’ to ‘equal partner’. The argument for this conceptual change is developed in three stages. First, we merge two concepts emerging from the literature, namely natural capital (or natural infrastructure) and infrastructure systems, to embed the natural environment as an integral component or ‘equal partner’ in port development. We then identify practical avenues through which the profile (or value) of the natural environment can be enhanced in port development, drawing on concepts such as Building with Nature (BwN) and multi-use of natural capital. Finally, we build a framework for Integrated Port Management (IPM) by conceptually positioning and aligning environmental processes within the traditional port development cycle, as well as identifying the need for coordination across and continuity between individual environmental assessment processes. In essence, bridging the disconnect between natural environmental issues and port development requires early consideration of the natural environment in port development, and an acknowledgement of multi-use benefits from natural capital. Further, in the operations and maintenance phases, environmental management systems in ports should not only focus on environmental performance, but also embrace multi-use valuation of the natural environment (ecosystem services) to give purpose to the need for environmental protection. However, crucial to effective implementation of an Integrated Port Management (IPM) framework will be its integration in organisational processes, supported by collaborative institutional structures. Only then will the environment take its place as equal partner in port development.
Winning suppletiezand Noordzee : scenariostudies m.b.t. slibtransport, nutriënttransport en primaire productie voor de periode 2013-2017
In dit rapport is het effect van zandwinning ten behoeve van reguliere kustsuppletie op slibconcentraties, doorzicht, nutrienttransport en primaire productie berekend middels numerieke modellen. In het rapport zijn met name de effecten in de Natura 2000-gebieden uitgebreid belicht.
Combustion in miscible displacement for high-pressure air injection
We develop a theory for the problem of high pressure air injection into deep reservoirs containing light oil. Under these conditions, the injected fluid (oxygen plus inert components) is completely miscible with the oil in the reservoir. Moreover, exothermic reactions between dissolved oxygen and oil are possible. We use Koval's model to account for the miscibility of the components, such that the fractional-flow functions resemble the ones from Buckley-Leverett flow. This allows to decompose the solution of this problem into a series of waves. We then proceed to obtain full analytical solutions in each wave. Of particular interest is the case where the combustion wave presents a singularity in its internal wave profile. Evaluation of the variables of the problem at the singular point determines the macroscopic parameters of the wave, i.e., combustion temperature, wave speed and downstream oil fraction. The waves structure was observed previously for reactive immiscible displacement and we describe it here for the first time for reactive miscible displacement of oil. We validate the developed theory using numerical simulations.