Risk analysis for new sea dike design guidelines in Vietnam

Abstract

Vietnam experienced sustained economic growth over the last decades, making it one of the fastest growing economies of the world. At this moment Vietnam is still fighting its way out of poverty and trying to improve living standards. With a coastline of 3,260 kilometers many activities take place in the densely populated coastal areas. The government of Vietnam wants to use the coastal zone to its fullest potential and therefore a lot of economic development is planned in these regions. It is important to make the coastal zones safe areas for living and investments. The coastal areas of Vietnam are protected from the sea by dikes. Currently a major sea dike project investigates and upgrades the sea dikes and creates new dike construction guidelines. This project consists of several subprojects which each focus on a specific task. Subproject 4 reviews the sea dikes from Quang Ninh to Quang Nam provinces (Northern coastal provinces). The subproject 4 contents are the collection of data on sea dikes, the creation of a sea dike databank, the determination of the dike route and to set up design criteria for sea dikes. Within subproject 4 the Safety Standards project was set up focused on a plan of approach to define sea dike safety standards with a risk-based approach. Design criteria and guidelines for the construction of sea dikes are (part of) the output of subproject 4 and safety standards can form part of these design criteria. To determine these safety standards a risk assessment is executed. This is a different approach with respect to the current situation and also is a complicated subject. Introducing this new approach for the Vietnam situation the Safety Standards project is the first step in implementing this strategy for coastal defense projects. The introduction of this method in Vietnam is considered more important than finding the exact safety standards for different situations. Therefore the results of the Safety Standards project should be regarded as indicative, as an example. Translation of safety standards to technical design criteria is therefore outside the project scope. The Safety Standards project uses the coastal provinces Hai Phong and Nam Dinh as case study areas. Both provinces have approximately the same size and number of inhabitants, but different characteristics. Hai Phong is a more industrial province; Nam Dinh is a rural province. The research is focused on the Vietnamese situation and done from a Vietnamese perspective. With calculations based on economic optimalization an approach of defining safety standards was developed and three different safety standards for the Vietnamese sea dikes were found: 1. High safety level for high developed and fast developing areas; a safety standard of 1/1000 years can be considered for these areas. 2. Medium safety level for moderate populated areas with sustained economic growth; a safety standard of 1/200 years can be appropriate. 3. Low safety level for rural areas with no to little development; this can be a safety standard of 1/100 years.