Urban areas are concentrations of flood risk because of the density of development and because they tend to be constructed in low‐lying areas. They may be subject to flooding from rivers or the sea but are also vulnerable to the effects of intense direct rainfall, which can overwhelm urban drainage systems, and cause complex and often localised patterns of pluvial flooding. The risk from pluvial flooding is particularly difficult to assess because it is sensitive to the spatial–temporal characteristics of rainfall, local run‐off and surface flow processes, the performance of urban drainage systems, and the exact location of buildings. Sampling the variability or uncertainty in all of these processes in order to generate accurate flood risk estimates quickly becomes computationally prohibitive, especially for large urban areas. In this paper, we evaluate alternative approaches for making use of high‐resolution spatial–temporal rainfall simulations in urban flood risk analysis. Flood depths are computed with a coupled sewer and surface flood model, and flood damage is estimated using standard depth‐damage criteria. Efficient sampling of rainfall events and judicious use of response surfaces that relate rainfall event properties to flood volumes and damages are evaluated and shown to reduce the computational expense of risk analysis by more than 70%. The risk analysis methodology is successfully demonstrated for two contrasting urban locations in the UK.
Construction of a culvert will impact ambient hydraulic characteristics such that upstream flow depths may increase due to any constriction at the inlet. Exacerbating this, flow can be further restricted within a culvert due to internal blockage by debris. Screens to prevent debris entering a culvert may also cause blockages, thus heightening the flood risk. In response to this problem, the research reported in this paper made use of a Froude-scaled physical model to investigate how screen blockage by debris is influenced by the geometry and positioning of a screen.Analysis based on 105 000 debris passes is used to show that, as expected, the potential for screen blockage by debris increases as the ratio of debris length to bar spacing increases. Furthermore, screen angle and position is shown to have a significant influence on blockage potential. This research involved the development of a methodology that can be used to assess the efficiency of different trash screen configurations. To build upon the analysis from this initial research and continue working towards the development of a predictive model that can aid future screen design, the research needs to be extended to look at the process of cumulative debris build up on screens.
NotationA screen angle D percentage of debris pieces blocked L debris length P ratio of flow velocity at the point of screen intersection with the water surface to a base upstream flow velocity measured at a distance equal to three channel widths upstream of the culvert inlet Q discharge S bar spacing
Pour expliquer le comportement des propriétés supraconductrices des alliages Al-Ag dans l'état de ségrégation en zones Guinier-Preston, nous proposons un modèle basé sur les effets de proximité entre phases normale et supraconductrice. Les résultats sont en accord avec l'hypothèse de l'existence d'une lacune de miscibilité contrôlant la croissance des zones
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