This investigation is to analyze the impacts of sea level rise and changes in fluvial flow on south coast of England. The River Arun was selected as a case study, and HEC-RAS program was chosen as the modelling software in this research. Hydrologic scenarios with combinations of different flow and sea level rise caused by climate change were used. The result shows that the current flood defences are sufficient to prevent flooding at present, but it is likely that a combination of sea level rise and a more active precipitation cycle will cause flooding. The various simulations show that, by constructing sluice gates at the mouth of the River Arun, the flood risk resulting from a 1 in 100 year river flow and sea level rise does not decrease. Indeed, the sluice gates somewhat increase the flood risk. While by selectively removing the flood embankments combining with constructing sluice gates at the mouth, the flood risk decreases. A clear trend of this case study is that the effectiveness of the engineering work drops to zero when sea level rises by a considerable value (say 1.0 m). The reason for this is that the increase in sea level leads to the rise of tide locked period, and the water stored within the upstream basin will eventually result in flooding.%分析了英国南部海岸海平面上升和径流增强对堤防的影响,选用HEC-RAS数学模型对阿伦河进行了研究,模型中采用了不同水文条件和工程组合.结果显示,就阿伦河而言,目前的防洪潮设施足以防御100 a一遇的洪水,但随着海平面的上升和降雨的加大,洪水风险也进一步增大.工程措施效果显示:仅在河口处建造水闸,不但不能抵御气候变化带来的灾害,反而将增大洪水风险;选择性地移除部分大堤,配合水闸的建设,将明显降低洪水风险,但当海平面上升到1m时,这个工程组合的功效快速减弱,原因在于随着海平面的上升,潮闸关闭的时间越来越长,径流将积累在上游并最终导致洪灾.
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