1642 research outputs found
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A review of dengue's historical and future health risk from a changing climate
No full textPurpose of review: The purpose of this review is to summarize research articles that provide risk estimates for the historical and future impact that climate change has had upon dengue published from 2007 through 2019.
Recent findings: Findings from 30 studies on historical health estimates, with the majority of the studies conducted in Asia, emphasized the importance of temperature, precipitation, and relative humidity, as well as lag effects, when trying to understand how climate change can impact the risk of contracting dengue. Furthermore, 35 studies presented findings on future health risk based upon climate projection scenarios, with a third of them showcasing global level estimates and findings across the articles emphasizing the need to understand risk at a localized level as the impacts from climate change will be experienced inequitably across different geographies in the future. Dengue is one of the most rapidly spreading viral diseases in the world, with ~390 million people infected worldwide annually. Several factors have contributed towards its proliferation, including climate change. Multiple studies have previously been conducted examining the relationship between dengue and climate change, both from a historical and a future risk perspective. We searched the U.S. National Institute of Environmental Health (NIEHS) Climate Change and Health Portal for literature (spanning January 2007 to September 2019) providing historical and future health risk estimates of contracting dengue infection in relation to climate variables worldwide. With an overview of the evidence of the historical and future health risk posed by dengue from climate change across different regions of the world, this review article enables the research and policy community to understand where the knowledge gaps are and what areas need to be addressed in order to implement localized adaptation measures to mitigate the health risks posed by future dengue infection
Local overshoot and wind effects on wave overtopping at vertical coastal structures
No full textWind effects on wave overtopping over a fully impermeable vertical sea wall are studied numerically using the open source CFD library OpenFOAM®. A pressure gradient correction term is incorporated in the momentum equations. In the range of wave conditions of the present studies, it is found that in the absence of wind, the increase of the wave steepness results in reduction of the wave overtopping. This is related to the instability of the standing wave formed at the front of a vertical structure. Such instability was noticed in the range of steepness between 0.285 and 0.443 from the previous physical experiments for a regular wave interacting with a vertical structure. In our numerical studies we confirm the existence of this regime. Our studies further show that the stability of the standing wave determines the shape and volume of the overshooting jet, which has a close effect on wave overtopping. When a wind is relatively weak, e.g. wind speed of 10m/s, it is unable to alter the shape and volume of the overshooting jet much, meaning a weak wind effect on wave overtopping. When a wind is strong, e.g. speed of 30m/s, it completely deforms the overshooting jet and volume, resulting in overtopping discharge almost 3 times of that without a wind
On the variability of flocculated particle characteristics in a shallow estuary
No full textWe conducted field work in South San Francisco Bay to examine cohesive sediment flocculation dynamics in a shallow, wave- and current-driven estuarine environment. Drawing on data collected using a suite of acoustic and optical instrumentation over three distinct seasons, we found that the factors driving floc size variability differed substantially when comparing locally-sourced sediment (i.e., through wave-driven resuspension) to suspended sediment advected from upstream. Statistical analysis of our extensive field data revealed additional seasonal variability in these trends, with wave stress promoting floc breakup during the summer and winter months, and biological processes encouraging floc growth during the spring productive period. Combining these data with fractal dimension estimates, we found that seasonally-varying floc composition can lead to differences in floc settling velocity by a factor of approximately two to five for a given floc size. Finally, by analyzing co-located turbulence and sediment flux measurements from the bottom boundary layer, we present evidence that the relationship between floc size and the inverse turbulent Schmidt number varies with floc structure. These results can be used to inform sediment transport modeling parameterizations in estuarine environments
EMBREA-MUD a tool for the simulation of tailings dams breaching
No full textFailure of a tailings dam can have disastrous consequences. However, to date, it cannot be accurately simulated. Therefore, the EMBREA-MUD model was developed to fill this gap within the DAMSAT project which is funded by the UK Space Agency. The model is a two component breach modelling tool that simultaneously takes into account outflows of both water and mud (i.e. tailings). The model can also represent erosion of dam material by both water and tailings, erosion of tailings by water as well as dynamic forces between water and tailings layer.
There are however some challenges related to simulation of tailings dam breaching and in particular the breach initiation which can be due to overtopping, piping or other mechanisms, such as foundation failure or sliding. As dams are designed to be stable, these initial failures are un-foreseen and therefore cannot be accurately quantified based on available data. In this paper, these mechanisms were investigated to check whether they could be reproduced assuming an initial notch in the dam crest. The case of Mount Polley was used, where the dam failed initially due to foundation failure. The results showed that the “initial notch” approach indeed produced similar peak outflows and time intervals
International Guidelines on Natural and Nature-Based Features for Flood Risk Management
No full textThe International Guidelines on NNBF for Flood Risk Management provide practitioners with the best available information concerning the conceptualization, planning, design, engineering, construction, and maintenance of NNBF to support resilience and flood risk reduction for coastlines, bays, and estuaries, as well as river and freshwater systems
Boussinesq-Type Modeling of Low-Frequency Wave Motions at Marina di Carrara
No full textIn this work, we carried out a case study of numerical simulations of low-frequency wave motions at the Marina di Carrara Harbor, where field observations have been conducted from 2005 to 2007. The fully nonlinear Boussinesq model, FUNWAVE-TVD, was applied to study the multiscale processes, including wind waves, infragravity waves, vortical eddies, and their potential effects on harbor operations. To reproduce the bound infragravity waves, the model was modified to take into account the second-order correction in wave generation based on weakly nonlinear second-order theory. Model–data comparisons show that the model correctly predicted the wave spectra in the low-frequency band and the overall long-wave energy inside the harbor. Additional numerical experiments, with different input wave characteristics, indicate that the directional spreading and incident wave direction play a role in predicting short waves inside the harbor, but have limited influence on the long-wave energy distribution, especially for the low-frequency band close to the resonant modes of the harbor. The second-order correction produces correctly the infragravity bands bounded with wave groups in the wave generation region. However, it does not modify the resonant modes and their magnitudes likely due to nearly “white” spectral structure, characterized by a nonzero constant power spectral density block or equivalently constant value/intensity of Fourier modes at different frequencies, in either bound or spurious infragravity waves
Simplified quantitative risk assessment for hydraulic gates
No full textIn many dam projects, the mechanical and electrical systems/components associated with the operation of spillway and low-level outlet gates can be regarded as ‘safety critical’. This is due to the fact that failure to operate gates as and when required can have a detrimental effect on the ability of the dam to pass flood flows. It should also be noted that gates and their operating mechanisms are particularly vulnerable during extreme events such as violent electrical storms, hurricanes and earthquakes. This paper will focus on spillway gates
Influence of projected climatic conditions and varying lateral points of release on oil slick transport in a tide-dominated estuary
No full textOil spills in estuarine systems can strongly endanger habitats and water quality. However, the impacts of projected climatic conditions on oil spill transport in estuarine environments have received little attention. To address these key gaps, we analyse here a range of simulations for the Humber Estuary, UK, using coupled hydrodynamic and oil spill model. These simulations indicate that, for this well-mixed macro-tidal estuary: (a) the influence of projected sea level rise and river discharge on oil slick impacted area, slick length and overall distance travelled is relatively minor (<10%); (b) magnitude of currents determines differences in dynamics between oil slicks released along the estuary length; and (c) differences in lateral current speed and direction are key determinants of the differences in the dynamics of oil slicks released along the estuary width. The implications of these findings for operational oil spill response in estuaries similar to the Humber Estuary are: (i) the need to be aware of dominant current direction in different segments of the estuary; and (ii) the need take cognisance of the interaction between oil slicks and estuary bank and how it influences overall distance travelled by oil slicks
Agent-based modelling of juvenile eel migration via selective tidal stream transport
No full textRecruitment of temperate eel species Anguilla anguilla, A. rostrata & A. japonica has declined over the last few decades due to human activities, such as overfishing and construction of migratory barriers (e.g. dams, weirs and sluices) and hazardous energy infrastructure (e.g. turbines, intakes and outfalls). Numerical models, substantiated with data from field and laboratory studies, can potentially predict and quantify the relative impacts of such activities, thereby assisting in the sustainable management of eel populations. Here, we present an agent-based model (ABM) of juvenile eel migration up estuaries. The model includes relevant eel behaviours and environmental conditions that, according to the literature, influence upstream migration. Crucially, by assessing the local salinity gradient and relative flow direction, the modelled eels (agents) self-determine whether the tide is flooding or ebbing and orientate themselves for navigation, with no top-down instructions. This allows the agents to decide which particular behaviour to undertake as part of Selective Tidal Stream Transport (STST). The developed ABM is coupled to a hydrodynamic model of the Thames Estuary and the results substantiated by comparison against eel trap data. Combinations of the various STST behaviours are systematically tested and the influence they have on up-estuary migration is assessed in terms of relative energy expenditure. The parameterised model is then used predictively at Milford Haven Waterway to investigate potential impacts on the juvenile eel population due to entrainment in a power plant cooling water intake and outfall. Results from the Thames model case study indicate that including bed anchoring behaviour is essential for achieving a good comparison with the eel trap data and the choice of salinity detection threshold is also important. If daylight avoidance (diel) behaviour is not included, the most energy efficient migration is achieved using just two STST behaviours (ebb tide bed anchoring and upward migration during flood). With diel behaviour included, energy expenditure is greater, but some efficiency is regained by including all of the STST behaviours. For the Milford Haven case study, the model predicted a juvenile eel intake and outfall entrainment rate of 2.0% and 4.7%, respectively. It is concluded that the ABM is a valuable tool for assessing potential impacts on the recruitment of eels (extendable to other species) and could be used to assist in site-selection and low impact design of energy infrastructure in tidal environments