The interaction between physical drivers from oceanographic, hydrological, and meteorological processes in coastal areas can result in compound flooding. Compound flood events, like Cyclone Idai and Hurricane Harvey, have revealed the devastating consequences of the co-occurrence of coastal and river floods. A number of studies have recently investigated the likelihood of compound flooding at the continental scale based on simulated variables of flood drivers, such as storm surge, precipitation, and river discharges. At the global scale, this has only been performed based on observations, thereby excluding a large extent of the global coastline. The purpose of this study is to fill this gap and identify regions with a high compound flooding potential from river discharge and storm surge extremes in river mouths globally. To do so, we use daily time series of river discharge and storm surge from state-of-the-art global models driven with consistent meteorological forcing from reanalysis datasets. We measure the compound flood potential by analysing both variables with respect to their timing, joint statistical dependence, and joint return period. Our analysis indicates many regions that deviate from statistical independence and could not be identified in previous global studies based on observations alone, such as Madagascar, northern Morocco, Vietnam, and Taiwan. We report possible causal mechanisms for the observed spatial patterns based on existing literature. Finally, we provide preliminary insights on the implications of the bivariate dependence behaviour on the flood hazard characterisation using Madagascar as a case study. Our global and local analyses show that the dependence structure between flood drivers can be complex and can significantly impact the joint probability of discharge and storm surge extremes. These emphasise the need to refine global flood risk assessments and emergency planning to account for these potential interactions.
MULTIFILE
Resilience is held as a promising concept to produce a paradigm shift from traditional flood control to an integration of flood risk management and spatial planning. Central ideas to the resilience narrative are that nothing is certain except uncertainty itself' and adaptability' is key to governing the unknown'. However, this terminology is far from clear, yet increasingly used, which raises the question how it is made sense of in practice. To answer this question, we examine two long-term flood risk management strategies in the London and Rotterdam region with a policy framing perspective (i.e. the English Thames Estuary 2100 Plan and the Dutch Delta Programme). In both strategies, uncertainties are a key concern, leading to adaptive strategic plans. Reconstructing the framing processes shows that the English adopted a scientific pragmatism' frame and the Dutch a joint fact-finding' frame. While this led to different governance approaches, there are also striking parallels. Both cases use established methods such as scenario planning and monitoring to manage' uncertainties. Similarly to previous turns in flood risk management, the resilience narrative seems to be accommodated in a technical-rational way, resulting in policy strategies that are maintaining the status quo rather than bringing about a paradigm shift.
The phenomena of urbanization and climate change interact with the growing number of older people living in cities. One of the effects of climate change is an increased riverine flooding hazard, and when floods occur this has a severe impact on human lives and comes with vast economic losses. Flood resilience management procedures should be supported by a combination of complex social and environmental vulnerability assessments. Therefore, new methodologies and tools should be developed for this purpose. One way to achieve such inclusive procedures is by incorporating a social vulnerability evaluation methodology for environmental and flood resilience assessment. These are illustrated for application in the Polish city of Wrocław. Socio-environmental vulnerability mapping, based on spatial analyses using the poverty risk index, data on the ageing population, as well as the distribution of the areas vulnerable to floods, was conducted with use of a location intelligence system combining Geographic Information System (GIS) and Business Intelligence (BI) tools. The new methodology allows for the identification of areas populated by social groups that are particularly vulnerable to the negative effects of flooding. C 2018 SETAC Original Publication: Integr Environ Assess Manag 2018;14:592–597. DOI: https://doi.org/10.1002/ieam.4077
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Nature-based coastal management is mainstream in the Netherlands. About 12 Mm3 of sand is added annually to the coast to compensate coastal erosion and maintain high safety levels against flooding. This amount will likely increase to compensate for accelerated sea level rise. (Mega-)Nourishments may also strengthen and support biodiversity and recreational values of the coastal zone and associated wetland areas. However, the ecological and societal impacts of mega-nourishments on open coasts are not well established, hampering comparison of pros and cons of different nourishment strategies. This knowledge gap is largely due to the lack of suitable methods to monitor and predict the spreading of nourishment sand along the coast and into tidal basins. Ameland Inlet provides us with a unique opportunity to develop and test novel approaches to fill this knowledge gap in close collaboration with our consortium and stakeholders. In 2018 the first tidal inlet mega-nourishment (5 Mm3) was placed in the Ameland Inlet ebb-tidal delta, and geomorphic and biotic responses nearby are closely monitored in the Kustgenese 2.0 and SEAWAD programmes. Our research builds on the insights gained, will gather new data to investigate off-site effects (linked with SIBES/SIBUS sampling), and build a common knowledge-base with stakeholders. We will develop novel luminescence-based methods to monitor the temporal and spatial dispersal of nourishment sand. These insights will be combined with an inventory of off-site biotic responses to nourishment and the role biota play in the mixing of nourishment sand with natural sediments. Combined results will be used to develop and validate models to trace transport paths of individual grains and improve morphodynamic predictions. Throughout the project, we will collaborate and interact intensely with coastal managers and (local) stakeholders to address concerns and exchange insights, creating a platform for co-assessment and optimization of nourishment designs and strategies.
