Thanks to excessive rainfall and several typhoons since this summer, there are many Chinese cities experiencing heavy rain, resulting in houses being flooded and garbage bins, billboards and cars floating on the streets.

According to a survey of 351 cities by the Ministry of Housing and Urban-Rural Development, 320 cities have experienced waterlogging, and 262 cities with floodwater at a depth of more than 50 mm account for 74.6 percent of the total. There are 220 cities that can drain water within 12 hours, and 57 cities that take more than 12 hours to drain water.

Waterlogging takes place in so many cities. It seems that it is caused by the short-term heavy rainfall and the small drainage pipe diameter or the insufficient drainage capacity. Among these factors, it is w

rth studying why the city has insufficient drainage capacity.

Rainfall and waterlogging are normal natural phenomena. In a not very large area, for example, say on 10 square kilometer of land, when the rain falls, it will naturally form a stream, then merge into a river, and then form a lake, which eventually flows to the sea. This is a natural phenomenon and a natural law.

If a city's drainage capacity is insufficient, it should restore natural drainage systems such as streams, riverbeds, lakes and wetlands to adapt to the nature.

Otherwise, no matter how wide we expand the city's drainage pipes, they are just child’s toys in the face of nature. Besides, large pipes can only be installed on the main street. It is impossible to avoid waterlogging when a city with an area of several hundreds or thousands of square kilometers only relies on a few small tubes on the road to drain water but without natural drainage systems. Things can only be worse when it happens in the plain areas. 

If we want to have enough drainage capacity, we can only restore the natural drainage systems such as streams, ponds, wetlands, riverbeds, and lakes. The big cities nowadays can occupy an area ranging from several hundreds to thousands of square kilometers. But in these cities, wetlands, ponds and small rivers have disappeared. The city drains water only depending on a few drain pipes and several small water outlets. It is inevitable that water will accumulate.

The drainpipes cannot replace the natural drainage system composed of streams, rivers, lakes and wetlands. To solve the problem of urban water accumulation, there are two ways.

First, human beings need to be humble and respect the natural ecology.

Today, human beings arbitrarily put themselves above nature, claiming to be the master of nature only because they boast scientific and technological strength such as digital technology, reinforced concrete and satellite positioning. Human beings should not lose their rationality, be bound by capital and interests, pursue the so-called agglomeration benefits, and make the city a huge workshop for capital gains. It is obvious that the city is getting worse every day.

Originally, urban planning was the means by which humans rationally constructed the city, but now it has become a tool serving capital and the market. People forget that the city is a part of nature and it is nurtured by nature. Now, the city expands at the cost of destroying natural landform. The natural drainage system disappears, and the city certainly has insufficient drainage capacity.

Human beings should return to rationality, and urban planning should stop designing mega-cities. The essence of urbanization is not how big a city can be, but whether every family can enjoy modern facilities.

Urban planning must serve both human development and nature. Only by respecting and obeying natural law can the city solve the problems such as waterlogging. The nature will punish us if we arbitrarily build large houses, and big cities.

Second, transform urban drainage projects in accordance with the laws of nature.

The city needs a complete drainage project. In the already built cities, it is necessary to construct artificial riverbeds (main drainage pipes), streams (drainage networks) and lakes (underground reservoirs), which are close to natural functions. If the diameter of the drainage pipe is not large enough, it must be upgraded. If the density of the drainage pipe network is insufficient, the density must be increased. Let the city reach the drainage capacity as the nature has.

It is easy to handle the riverbed (main drainage pipe network) and the stream (supporting drainage pipe network), but it is difficult to build a lake in the city. We cannot demolish anyone’s house. Building lakes is a viable solution to the urban waterlogging. As early as 542 AD, the Byzantine Empire in Europe built a groundwater palace (groundwater reservoir) that could store 100,000 tons of water.

Today, Japan has built such an underground lake in Saitama Prefecture near Tokyo. It took more than ten years and $3 billion to build the lake with a depth of 65 meters and 50 meters under the ground. It is impossible to build a lake as large as several square kilometers, even if it is built in the underground of the city. The Japanese installed a water pump in this underground lake, which can discharge 200 cubic meters of water per second to the sea, and finally solved some of the water problems in the city of Tokyo.

What is important for renovating the urban drainage project is investment, the amount of which might be several times of the previous investment. This is the price that human must pay after they blindly expand the city and destroy the natural ecology.

Urban drainage is a public service (public goods). The government and public finances must assume responsibility. During the 13th Five-Year Plan period (2016-2020), the state plans to allocate 564 billion yuan ($82.5 billion) of funds, but the money used on the construction of sewage treatment plants and the urban drainage pipe network merely accounts for one third. It is far from enough to transform the urban drainage system in over 2,600 cities around the nation. It may be possible for five or six cities to build an underground lake (underground reservoir) like Tokyo. What about the funds for drainage renovation projects in thousands of cities?

It is not viable to apply public-private partnerships (the so-called PPP model). Urban drainage is a public service (public product) that cannot be operated and is not profitable. It must be invested by the government through taxes paid by citizens and businesses. When public finances are insufficient, the government can issue project bonds or apply for loans, but the assets must be public.

Xu Zongwei is former general director of policy at the Ministry of Housing and Urban-Rural Development. The views do not necessarily reflect those of China Watch.

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