**5. The Heritage Value and Utilization of Urban Form**

UNESCO seeks to encourage the identification, protection and preservation of cultural and natural heritage around the world considered to be of outstanding value to humanity. This admirable endeavor is embodied in an international treaty called the Convention concerning the Protection of the World Cultural and Natural Heritage, which was adopted by UNESCO in 1972. Since then, not only has the term "world heritage" come into being, but there is also a worldwide common understanding of cultural and natural values. The Convention thus embodies the values of the human subject today. Up to now, 845 cultural heritage sites, 209 natural heritage sites and 38 mixed cultural and natural heritage sites have been selected for the World Heritage List (http://whc.unesco.org/en/list). Among them, China has 36 cultural heritage sites, 13 natural heritage sites and four mixed heritage sites. According to the definition of "World Heritage Convention" and operational guidelines for the Implementation of the World Heritage Convention, the case of this study, Kaifeng city, together with the Yellow River Dams and the lower Yellow River, should, arguably, be included in the World Heritage List as cultural and natural mixed heritage sites. According to the study of Zhou [46,47], the Yellow River Dams meet the standards of cultural heritage iii, iv and v, and the lower Yellow River meets the standards of natural heritage vii and viii. Furthermore, we suggest that Kaifeng city meets the standards of natural mixed heritage. According to the first article of cultural heritage in the World Heritage Convention, Kaifeng city meets the three definitions of cultural relics, group of urban buildings or historic towns and urban center, and sites. At the same time, it is in accordance with the UNESCO Recommendation on the Historic Urban Landscape [48]. Kaifeng city has nine Major Historical and Cultural sites protected at National Level, nine provincial-level key cultural relics' protection units in Henan province, and more than 200 non-removable cultural relics. There are three historical blocks: Shudian Street, Imperial Song Street and Shuanglong lane. The sites of the Northern Song Dynasty ruins were included in the 13th Five-Year special plan for the protection of China's great national ruins. The immovable cultural relics on the ground and the underground piled city sites in Kaifeng together constitute the remarkable characteristics of the centralized distribution of cultural relics, high level of protection and great value impact.

The historic urban landscape is the urban area understood as the result of a historic layering of cultural and natural values and attributes, extending beyond the notion of "historic centre" or "ensemble" to include the broader urban context and its geographical setting. Kaifeng City can meet the four standards of operational guidelines for the Implementation of the World Heritage Convention. The suspended rivers in the lower Yellow River are generally 2~5 m above the ground. But in the Kaifeng reach, the height difference between the riverbed and the urban area is more than 13 m, which is the most typical reach of the lower Yellow River floodplain. The three-dimensional urban

flood control system of Kaifeng city, formed in the long-term struggle with the flood and sediment disasters of the Yellow River, is composed of the "Yellow River Dams–City earth rampart moat-brick wall–inner lake" and other adaptive landscapes. It is, also, an outstanding achievement of adapting or transforming the natural environment and has important values regarding landscape and urban planning and design in the lower Yellow River floodplain.

Although Kaifeng city had two catastrophic disasters (i.e., 225 BC and 1642 AD) and there have been several suggestions of moving the city to other areas, the succession and development of different periods remained within the earth rampart, a testament to the struggling spirit of Kaifeng people. According to the analysis of urban archaeology and stratigraphy, the inheritance of the cities buried under Kaifeng city in different periods is more prominent and outstanding, and they need to be protected for the world to share. As a whole historic urban landscape, there are only three sites selected for the world cultural heritage list in China, namely, the Ancient City of Ping Yao, Old Town of Lijiang and Historic Centre of Macao [49]. As long as we fully understand and explore the heritage value of Kaifeng city, it is anticipated that the city will be included in the list of world cultural and natural mixed heritage sites.
