Structure and Functions of Urban Surface Water System in Coastal Areas: The Case of Almere

In the context of global climate change, flooding and sea level rise is increasingly threatening coastal urban areas, in which large population is continuously concentrated. Dutch experiences in urban water system management provide high reference value for sustainable coastal urban development projects. Preliminary studies shows the urban water system in Almere, a typical Dutch polder city, have three kinds of operational modes, achieving functions as: (1) coastline control – strong multiple damming system prevents from storm surges and maintains sufficient capacity upon risks; (2) high flexibility – large area and widely scattered open water system greatly reduce local runoff and water level fluctuation; (3) internal water maintenance – weir and sluice system maintains relatively stable water level, providing excellent boating and landscaping service, coupling with water circulating model maintaining better water quality. Almere has provided plenty of hints and experiences for ongoing development of coastal cities in emerging economies. Keywords—Coastal area, resilience, sustainable urban water system, water circulation. I. RESEARCH BACKGROUND A. Population Concentration in Coastal Areas Coastal areas are some of the most productive land on earth and are good locations for global trade. These belt-like regions were continuously concentrating large number of population in the past decades, and now turned into the most intense urban development area in the planet. According to 2003 data, 2,385 million people live within the coastal limit, which represents 41% of world global population. More than 50% of the coastal countries have from 80 to 100% of their total population within 100 km of the coastline. Twenty-one of the 33 world's megacities are found on the coast [1]. If the trends observed between 1990 (2 billion people living within 100 km of the coast) and 2000 (2.3 billion) continue, the UN Population Division estimates that the number of people living on and around coastlines will increase to 3.1 billion people by 2025 (an approximately 34% increase in population) [2]. There are more than 3,000 cities in the low elevation coastal zones around the world. Of these cities, almost 65 percent are in developing countries. Many experts argue that cities will have to cope with almost all of the population growth to come in the next two decades, and much of this increase will occur in coastal urban centers [3]. Close to 60% of China’s population The project is supported by International Science & Technology Cooperation Program of China (2010DFA74490) Tao Zou is with School of Architecture, Tsinghua University, Beijing, 100084 China (phone: +86(10)62773094; e-mail: zoutao@ vip.sina.com). Zhengnan Zhou is with School of Architecture, Tsinghua University, Beijing, 100084 China (phone: +86(10)62773094; e-mail: zznan@ mail.tsinghua.edu.cn). live in 12 coastal provinces, along the Yangtze River valley, and in coastal megacities. Along China’s 18,000 kilometers of continental coastline, population densities average between 110 and 1,600 per square kilometer [4]. B. Challenges to Urban Development in Coastal Areas Coastal zones are highly vulnerable to sea levels rise when considering global climate change. Stronger and higher frequency of storm surges poses an increasing threat to coastal urban area, and especially to the infrastructure system. The main issues are flooding, water resources, land loss and many others as well. Coastal population growth increases demand for a continuing supply of clean water, waste disposal, public health, food and protection from natural disasters. There are also increased pressures on ecosystems from recreation and tourism, and from the infrastructure needed to accommodate these in the form of roads, bridges, parking lots and sewers [5]. Human settlements located in coastal regions are very vulnerable to extreme weather events. An increase of such events as a result of global climate change is likely to cause significant damage related costs. In recent years, large number of new commercial and residential development in China also concentrates in coastal areas. Especially in megacities like Shanghai and Tianjin, or city clusters located around them, dozens of new-towns with a planned population from 100,000 to 500,000 emerges along coastal low-lying belts, among which Sino-Singapore Tianjin Eco-city is one of the most known projects. Sea level rise may cause immense economic loss due to the direct or indirect damage to the urban areas, sewers, ports and other infrastructure. Simultaneously the quality of water is likely to decrease, with the fluctuation of runoff that either increased sediments and pollutants or decreased flushing that leads to higher salinity levels. In north China coastal cities, increased salinity is vastly threatening water quality for residential users and affecting crops as well. Many coastal lowlands, especially in the developing world, have limited or no human-built protection against impacts from sea level rise or storms. How to deal with the challenges of achieving sustainable development in the coastal zones is a key issue for future global sustainable vision. In this respect, the urban development of low-lying coastal zone in the Netherlands provides significant value as a reference. Structure and Functions of Urban Surface Water System in Coastal Areas: The Case of Almere Tao Zou, and Zhengnan Zhou World Academy of Science, Engineering and Technology International Journal of Civil, Environmental, Structural, Construction and Architectural Engineering Vol:6, No:11, 2012 954 International Scholarly and Scientific Research & Innovation 6(11) 2012 scholar.waset.org/1999.3/168 In te rn at io na l S ci en ce I nd ex , A rc hi te ct ur al a nd E nv ir on m en ta l E ng in ee ri ng V ol :6 , N o: 11 , 2 01 2 w as et .o rg /P ub lic at io n/ 16 8 II. URBAN DEVELOPMENT AND WATER SYSTEM FUNCTIONS IN