Dealing with the issue of urban storm water flooding is becoming increasingly urgent. In the Netherlands there are no clear guidelines on the level of acceptance of urban flooding. Based on an accurate DEM, a detailed quick scan tool has been used to assess an extreme storm event in Amsterdam. The resulting flood maps for the whole of the city show where flooding is likely to occur after 60 or 100 mm of rain in one hour, as well as which buildings are at risk.Based on the results from this mapping study, Amsterdam decided to start a program to make the city rainproof (Amsterdam Rainproof). Part of the program was the validation of the model based on field research. An example of this is the use of data from the extreme storm event that occurred in Amsterdam on 28 july2014. In this paper several pilots from Amsterdam will address the relevance and effectiveness of the quick scan tool.
Since 1990, natural hazards have led to over 1.6 million fatalities globally, and economic losses are estimated at an average of around USD 260–310 billion per year. The scientific and policy communities recognise the need to reduce these risks. As a result, the last decade has seen a rapid development of global models for assessing risk from natural hazards at the global scale. In this paper, we review the scientific literature on natural hazard risk assessments at the global scale, and we specifically examine whether and how they have examined future projections of hazard, exposure, and/or vulnerability. In doing so, we examine similarities and differences between the approaches taken across the different hazards, and we identify potential ways in which different hazard communities can learn from each other. For example, there are a number of global risk studies focusing on hydrological, climatological, and meteorological hazards that have included future projections and disaster risk reduction measures (in the case of floods), whereas fewer exist in the peer-reviewed literature for global studies related to geological hazards. On the other hand, studies of earthquake and tsunami risk are now using stochastic modelling approaches to allow for a fully probabilistic assessment of risk, which could benefit the modelling of risk from other hazards. Finally, we discuss opportunities for learning from methods and approaches being developed and applied to assess natural hazard risks at more continental or regional scales. Through this paper, we hope to encourage further dialogue on knowledge sharing between disciplines and communities working on different hazards and risk and at different spatial scales.
Nature-based strategies, such as wave attenuation by tidal marshes, are increasingly proposed as a complement to mitigate the risks of failure of engineered flood defense structures such as levees. However, recent analysis of historic coastal storms revealed smaller dike breach dimensions if there were natural, high tidal marshes in front of the dikes. Since tidal marshes naturally only experience weak flow velocities (~0-0.3 ms-1 during normal spring tides), we lack direct observations on the stability of tidal marsh sediments and vegetation under extreme flow velocities (order of several ms-1) as may occur when a dike behind a marsh breaches. As a first approximation, the stability of a tidal marsh sediment bed and winter-state vegetation under high flow velocities were tested in a flume. Marsh monoliths were excavated from Phragmites australis marshes in front of a dike along the Scheldt estuary (Dutch-Belgian border area) and installed in a 10 m long flume test section. Both sediment bed and vegetation responses were quantified over 6 experimental runs under high flow velocities up to 1.75 ms-1 and water depth up to 0.35 m for 2 hours. These tests showed that even after a cumulative 12 hours exposure to high flow velocities, erosion was limited to as little as a few millimeters. Manual removal of the aboveground vegetation did not enhance the erosion either. Present findings may be related to the strongly consolidated, clay- and silt-rich sediment and P. australis root system in this experiment. During the flow exposure, the P. australis stems were strongly bent by the water flow, but the majority of all shoots recovered rapidly when the flow had stopped. Although present results may not be blindly extrapolated to all other marsh types, they do provide a strong first indication that marshes can remain stable under high flow conditions, and confirm the potential of well-developed tidal marshes as a valuable extra natural barrier reducing flood discharges towards the hinterland, following a dike breach. These outcomes promote the consideration to implement tidal marshes as part of the overall flood defense and to rethink dike strengthening in the future.
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‘Dieren in de dijk’ aims to address the issue of animal burrows in earthen levees, which compromise the integrity of flood protection systems in low-lying areas. Earthen levees attract animals that dig tunnels and cause damages, yet there is limited scientific knowledge on the extent of the problem and effective approaches to mitigate the risk. Recent experimental research has demonstrated the severe impact of animal burrows on levee safety, raising concerns among levee management authorities. The consortium's ambition is to provide levee managers with validated action perspectives for managing animal burrows, transitioning from a reactive to a proactive risk-based management approach. The objectives of the project include improving failure probability estimation in levee sections with animal burrows and enhancing risk mitigation capacity. This involves understanding animal behavior and failure processes, reviewing existing and testing new deterrence, detection, and monitoring approaches, and offering action perspectives for levee managers. Results will be integrated into an open-access wiki-platform for guidance of professionals and in education of the next generation. The project's methodology involves focus groups to review the state-of-the-art and set the scene for subsequent steps, fact-finding fieldwork to develop and evaluate risk reduction measures, modeling failure processes, and processing diverse quantitative and qualitative data. Progress workshops and collaboration with stakeholders will ensure relevant and supported solutions. By addressing the knowledge gaps and providing practical guidance, the project aims to enable levee managers to effectively manage animal burrows in levees, both during routine maintenance and high-water emergencies. With the increasing frequency of high river discharges and storm surges due to climate change, early detection and repair of animal burrows become even more crucial. The project's outcomes will contribute to a long-term vision of proactive risk-based management for levees, safeguarding the Netherlands and Belgium against flood risks.
Er wordt continu ‘reuzenarbeid’ verricht in het rivierengebied in het teken van hoogwaterbescherming, vaarwegbeheer, natuurontwikkeling en delfstoffenwinning. Bij veel van deze rivierprojecten maakt grondverzet het grootste deel uit. Het is onder andere bepalend voor de kosten, de CO2-footprint en de omgevingshinder van dergelijke projecten, en de ruimtelijke kwaliteit van het rivierlandschap. Slim omgaan met grond is daarom een sleutelfactor van duurzaam rivierbeheer. Het onderwerp heeft daarom een prominente plek in verschillende kennis- en innovatieagenda’s, zoals de KIA Landbouw, Voedsel en Water, de KIA Circulaire Economie, en de KIA van het Hoogwaterbeschermingsprogramma. Deze articuleren een behoefte aan praktijkgericht onderzoek dat bijdraagt aan verduurzaming en kostenreductie van grondverzet, zodat grondverzet in 2030 energieneutraal is, de kosten per m3 tussen 2020 en 2030 aanzienlijk gedaald zijn en dat er in 2030 een gezonde slibeconomie is voor circulair materiaalgebruik. Desondanks moet er nog heel wat water door de Rijn voordat bovenstaande ambities in de praktijk kunnen worden gehaald. Het doel van dit project is om praktische inzichten en tools voor duurzaam grondmanagement in riviergebieden te ontwikkelen. Een consortium van 22 partijen (publiek, privaat, kennis) zal onder leiding van HAN lectoraat Sustainable River Management praktijkgericht onderzoek doen ter ondersteuning van technisch managers, ontwerpers, risicomanagers, projectmanagers en beheerders van dijken en uiterwaarden. Door middel van o.a. materiaalonderzoek, ontwerpend onderzoek en evaluaties worden praktische handvatten ontwikkeld voor realisatiestrategieën voor grondstoffenwinning volgens het DNA van de rivier, en het bruikbaar maken van sediment en gebiedseigen grond voor toepassing in de dijkenbouw. Bovendien worden verbeterde werkwijzen en tools ontwikkeld voor het op riviertakniveau afstemmen van vraag en aanbod van delfstoffen in natuur- en dijkversterkingsprojecten in het rivierengebied. Hiermee levert het project een concrete bijdrage aan de invulling van het Grondstoffenakkoord en het Rijksprogramma ‘Nederland Circulair in 2050’.
