The biggest problems of urban construction in China are city scale, water resources, traffic and environment. The most direct manifestation of urbanization process is also the scale of the city, which can make rational and economic use of resources. Among them, three decisive factors are water, traffic and environment. According to statistics, there are 300 water-deficient cities in China, 40 of which are in trouble, and Beijing is one of them. It should not be said that cities are short of water. It should be accurately said that these cities were not short of water originally, just because of the disorderly expansion of cities and the sharp increase of population for decades, which caused water shortage, just like Tianjin introduced the Luanhe River into Tianjin. People sometimes pay more for water than for rebuilding a city. Many countries in the Middle East desalinate seawater, and water is more expensive than oil. There was a famous Silk Road in the Tang Dynasty, and the western regions flourished for hundreds of years. Later, most of these ancient cities died out, and the most important reason was the lack of water. Water not only determines the size of the city, but also is the lifeblood of the city. The ancients took the well as their hometown, and the hometown was almost the same language. Many villages declined and disappeared due to lack of water or water. Hong Kong cannot survive without mainland water sources. The most famous ancient capitals in the history of China, such as Xi, Luoyang and Kaifeng, were all built by rivers. There are no rivers in Beijing, but in the late Qing Dynasty, 19 1 1 had only 760,000 people, and the area was only as big as the second ring road, so there was enough groundwater. Now the population of Beijing has expanded to 7 million, and the underground surface water has reached its limit. How to solve the water problem in Beijing has become a major issue related to the development and destiny of the capital. Nowadays, with the development of economy and the acceleration of urbanization, people must conduct a comprehensive demonstration of water sources when formulating the overall urban planning, and can no longer build water-deficient cities. ● The scale of urban construction is not as big as possible. People can realize that the size of a city is inversely proportional to the quality of traffic, that is, the bigger the city, the worse the traffic. The smaller the city, the better the traffic. There are traffic jams in big cities, and traffic jams and big cities have almost become the same language. Theoretically speaking, when the city is big, the distance between people's living and office, life and shopping will increase, and the time spent on the road will inevitably increase. People are going to work now, so they should reserve an hour or two for transportation. The bigger the city, the wider people's traffic range and the longer they stay on the road. The longer you stay on the road, the heavier the traffic will be. As a result, time and resources are wasted and pollution is increased. ● Experts believe that a city with a radius of five kilometers and a population of 500,000 has the best scale. We pursue convenient, economical and pollution-free urban transportation. With this goal, the scale of the city to be formulated or planned should be: the city with a radius of half an hour by bike is the best, that is, the city with a radius of 5 kilometers and a population of less than 500 thousand is the best. The reason why bicycles are used as a yardstick to measure the convenience of transportation and the size of a city is very simple. Bicycle is the only modern means of transportation that does not consume oil resources, is pollution-free and uses the most. Looking at the development of Beijing by this standard, the best scale is the ancient city wall, which is now within the Second Ring Road. If Beijing is still as big as it is now, the traffic problem will be extremely easy to solve, or as Mr. Liang Sicheng imagined, a new Beijing will be built outside old Beijing, which looks like two dumbbells. It is also a good plan to connect the middle with the subway expressway. Unfortunately, these opportunities have been missed. Some experts say that if the urban area of Beijing becomes the size of the Fifth Ring Road one day, Beijing's traffic will be in an extremely difficult situation. Even if people pay a huge price for it, they can't change the situation of traffic congestion. Summing up historical lessons, we can no longer let the city expand blindly and disorderly. The consequences of this expansion have been confirmed by many cities in western developed countries. Running to the city, abandoning the city and running to the suburbs, this kind of waste is repeated, which is the so-called "failure of the city." Traffic restricts the development of the city. Although science and technology constantly improve transportation modes and tools, it can also improve urban traffic. For example, the subway and high-speed trains on the ground in Tokyo, Japan, more or less offset the disadvantages of big cities. However, pollution, high energy consumption and long time spent on transportation still cannot be eliminated, and the urban construction of China should learn from it. The superiority of multi-center system cities over single-center cities not only restricts the scale of cities, but also determines the form of urban planning. 1882, 100 years ago, a Spanish engineer designed a strip-shaped city. The planning principle is that the traditional urban form extending from the core is out of date, while a modern city should take wide roads and water heating and electricity trunk lines as the backbone, the width of the city should be limited, and the length of a strip city can be unlimited. Other urban planning, such as finger-shaped urban planning, the transition from single-center structure to flexible multi-center system, all take traffic as the primary design basis. Even the miniature monomer design is no exception. The relationship between residential quarters and adjacent main roads, and the reasonable traffic layout of office and residence are the first factors to be considered in the design. Greening is the eternal theme of urban construction, and the environment determines the development direction of the city. People should not only see "green", but also breathe the air of fields and oceans, as well as the clear blue sky and sunshine. In foreign countries, people's aversion to big cities is increasing day by day, and as a result, garden cities, suburbanization and non-central cities have emerged. We have no choice but to see that in the era of rapid development, the development of many cities in our country has blindly emphasized the social environment of cities. For example, simply pursuing an international metropolis, blindly building high-rise buildings and blindly building super-large residential areas. Although big cities spend a lot of manpower and money to improve environmental sanitation, they still lag behind small and medium-sized cities in evaluation. Limiting the size of big cities has become a common voice in the world. People have to seriously consider people's needs for the natural environment. First of all, people are forced to change the past planning and design ideas, from simple material construction and ornamental art to "harmony between man and nature" and return to nature, and become a comprehensive place to pursue the harmony between man and society and nature and meet people's various requirements. In the mid-20th century, the urbanization process in various countries changed from blind disorder to conscious order, and from land speculation to rational planning under government control. People coordinate the distribution of productive forces and regional integration. According to the principles of economic development, scientific education and cultural development, ecological environment and protection, resource investigation and sustainable development, the most reasonable development plan is formulated by systematic engineering, which is generally translated into laws and regulations. In the process of pursuing eco-city and stepping into the eco-era, countries all over the world have gained many experiences that attract worldwide attention. For example, Moscow multi-core planning in Russia, the third generation new city in Britain and France, and the three sub-centers in Tokyo, Silicon Valley and Metropolitan Interlocking Area in the United States ... In short, the natural environment plays a leading role in the development direction, layout and scale of urban construction. ● Disadvantages in urban construction From the perspective of population, the proportion of urbanization in China is less than 30%, and that in developed countries is more than 70%. With the rapid development of China's economy, the process of urbanization will be accelerated. However, it is not advisable to pursue a high proportion of urbanization, because economic development will eventually eliminate the differences between urban and rural areas. Nowadays, the suburbs of the most developed countries in the world can't distinguish the boundaries between cities and rural areas. In the process of rapid urbanization, the most terrible thing is blindness. The weakness of urban planning talents and theories in China has aggravated this blindness. China has long put forward the policy of restricting big cities and developing small and medium-sized cities. The planning law promulgated by 1989 emphasizes this point again. However, in the specific implementation process, due to the lack of compliance with laws and lax enforcement, it has actually become a slogan. In the process of urbanization in western developed countries, some scientific plans cannot be realized, and the biggest obstacle is the out-of-control of land private ownership and land speculation. Both of them have led to the expansion of the city again and again. Nevertheless, it still can't keep up with the increase of population, which leads to the deterioration of urban environment, traffic jams, exceeding the tolerance limit, the decline of downtown, and the rich people flock to the suburbs and enter a vicious circle. This is a common problem in the process of urbanization in the West in the decades after World War II. In the past ten years, with the prosperity of the real estate industry, cities in China have developed rapidly, and some cities have reached the limit. The reason for losing control is that some local officials and businessmen join hands and rely on the will of the chief executive, and there is no detailed regional and urban planning that has been scientifically demonstrated, which stays at the primary level of single building approval. Even regardless of the incomplete infrastructure, blindly launched, first built on the ground, and then built underground. Demolition of buildings is even more wasteful. This is the main problem in the process of urbanization in China, and its harm is very serious: 1. Due to the underestimation of water resources, there are currently 300 water-deficient cities out of 500 cities in China. The annual loss was 654.38+000 billion yuan, and this situation continues. 2. With the expansion of the city, the transportation cost increases. The way out for transportation in the world's megacities is to develop subways. The cost of subway is about 400 million yuan per kilometer. According to the level of 30-year-old 177-kilometer subway in Mexico City, China's four cities will need 280 billion yuan, with an average of nearly10 billion yuan per year. With the increase of megacities in China, the investment in transportation construction will inevitably increase. Obviously, controlling the size of the city will reduce and save huge amounts of money. 3. Urban traffic planning lags behind economic construction. Many projects are to build roads in Gai Lou first, or to tear down buildings and expand roads, which is both a waste of money and difficult to calculate. The garbage disposal fee in big cities is raised to one gram of gold per ton. The bigger the city, the more difficult it is to control the environment, the more expensive it is, and the more serious it is to people's health. Because our country has a large population, the feasible countermeasure is to actively promote the construction of small towns. The city scale of many big cities has reached the limit from the beginning, and the re-expansion is "the failure of the city", and only the multi-center transformation, optimization and development can be carried out in the restricted or frozen city scale. Therefore, the development of big cities can only rely on small towns, which will inevitably become the mainstream of urbanization in China. Relevant laws and regulations should clarify all new first-and second-class industrial projects, and try to locate them in small towns far from big cities where resources permit. Development zones should also rely on such small towns. In other words, the urbanization trend of China should develop to small towns, and new development and new projects should be closely integrated with the development of small towns as far as possible. It won't be long before, with more than 40% of China's urban population in ten or twenty years, the future of China's urbanization should be a small garden-like city with a population of less than 500,000. By then, pearl cities like Weihai and Zhuhai will be densely covered in China.