Risk based approach for safety standard of coastal flood defences in Vietnam
Risk based approach for safety standard of coastal flood defences in Vietnam
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基于风险的越南沿海防洪安全标准方法
DOI：
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发表时间：
2008
期刊：
影响因子：
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通讯作者：
Nguyen Ba Quy
中科院分区：
文献类型：
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作者：
M. V. Công;M. C. Tri;Nguyen Ba Quy
本文重点讨论越南沿海防洪的风险分析和安全问题。海堤系统实际上是按20至25年重现期设计的。从目前的情况来看，堤防系统不足以承受实际的海面边界条件。目前越南每年因洪水和台风造成的经济损失总额约为GDP的1.0%至1.2%。因此，对现有海防体系进行准确的安全评估具有重要意义。它可以量化防御系统失效、生命损失、经济、环境、文化损失和其他无形资产后可能产生的后果。为了确定安全是否足够安全，本文进行了一项调查，以确定除洪水风险之外当地居民面临的其他类型的风险。本文讨论的问题可以帮助决策者找到沿海地区的最佳保护水平，并制定越南沿海防洪恢复的长期规划。 1.1 背景 沿海防洪系统可包括多种要素，即海堤段、河口堤段、沙丘、海堤、堤坝穿越结构和排水结构。该系统旨在通过规范中规定的一定安全级别来保护低洼沿海地区免受洪水侵袭。主要兴趣是保护区的实际安全性如何以及是否足够安全。第一个问题是通过量化保护区被淹没的概率，或者换句话说，系统故障发生的概率来回答的。后一个问题的答案可以通过确定保护区可接受的风险水平来给出。通过概率设计方法可以准确量化被淹没（失败）的概率。在过去的几十年里，这种方法在土木工程领域越来越多地被提出、应用和发展（例如参见 Rackwitz 1977 年；Ditlevsen 1979 年；Bakker & Vrijling 1980 年；Vrijling 等人 1998 年；van Gelder 1999 年；Oumeraci 等人 2001 年；和 Voortman 2002 年的概念、方法和应用）。概率设计方法的基本优点是它基于所考虑系统的可接受的故障频率；考虑输入参数的不确定性并将其视为随机变量；通过各种可能的失效模式描述结构的失效；并找到整个系统发生故障的真实概率
This paper focuses on risk analysis and safety aspects of coastal flood defences in Vietnam. The sea dike system has been actually designed by a 20 to 25 years return period. From the current situation it seems that the dike system is not sufficient to withstand the actual sea boundary condition. As present situation the total annually economic damages of Vietnam due to floods and typhoons is about 1.0 to 1.2 % of its GDP. Accurate safety assessment of the existing coastal defence system is, therefore, of large importance. It can quantify the possible consequences after failure of the defensive system, the loss of life, economic, environmental, cultural losses and further intangibles. To determine if safe is safe enough, an investigation is carried out in this paper to determine other types of risks to which the local population is exposed, apart from the flood risk. The issues addressed in this paper may support decision-maker to find the optimal protection levels of the coastal regions and for a long term planning of rehabilitation of the coastal flood defences in Vietnam. 1.1 Backgrounds A coastal flood defence system may comprise various elements i.e sea dike sections, estuarine dike sections, dunes, sea walls, dike crossing structures and discharged structures. The system is designed to protect low-lying coastal zone from sea floods by a certain safety level which is written in the codes. Main interests are what is the actual safety of the protected areas and if safe is safe enough. The first question is answered by quantification of probability that the protected areas are inundated or, in other word, the probability that the system failure occurs. Answer for the later issue can be given by determination of acceptable risk level for the protected regions. The inundated (failure) probability can be quantified accurately by probabilistic design method. This approach has been increasingly proposed, applied and developed in the fields of civil engineering during the last decades (see e.g. the concepts, methods and applications in Rackwitz 1977; Ditlevsen 1979; Bakker & Vrijling 1980; Vrijling et al. 1998; van Gelder 1999; Oumeraci et al. 2001; and Voortman 2002). Fundamental advantages of probabilistic design approach are that it is based on an acceptable frequency of failure of the considered system; take into account the uncertainties of the input parameters and treat them as the random variables; describe failure of the structures by various possible failure modes; and find a true probability of failure of the whole system