What are the reasons for urban waterlogging?
First, climate change leads to changes in the water cycle. Due to the increase of urban population density, man-made heat removal, air pollution and heat island effect lead to further changes in the water cycle, thus causing changes in urban microclimate.
Second, urban development and construction caused by the ground natural stagnation and rainwater storage capacity decreased.
Third, the drainage capacity of drainage facilities such as drainage pipes and canals is insufficient.
The fourth is human factors. Long-term over-exploitation of groundwater leads to land subsidence; Poor construction management causes construction waste or domestic waste to block the pipeline; Pump station failure; Landscape Avenue reconstruction coverage or manhole cover damage.
Characteristics of urban waterlogging
Urban waterlogging is very common in China. Judging from the occurrence areas, some coastal areas with relatively low terrain and inland cities with large precipitation. In the past, the urban construction land area was small and the optional area was relatively large; Generally speaking, urban construction is to choose high-lying places, but now urban land is very tight and there is little choice.
In some specific parts of the city, such as overpasses, the incidence rate is higher. With the construction of modern cities, many new problems have emerged in drainage. In many places, under the overpass, water will accumulate after rain. Similar situations exist in underpasses, railway bridges and highway bridges crossing the street.
Urban waterlogging can occur in any area, but it is not said that it is mainly distributed in urban design research. From a global perspective, the probability of urban waterlogging in developing countries is relatively high, while that in developed countries is relatively low. In some cities and regions where waterlogging is common, in the early stage of urban construction, the pavement structure design is unreasonable and insufficient attention is paid to pavement waterlogging; But judging from some western buildings, this is a major design accident, which will bring great negative impact on urban life.
How to deal with urban waterlogging
1 First of all, cities should make good plans for flood control and waterlogging prevention.
The data of urban topography, underlying surface, drainage pipe network, river hydrological data and meteorology should be collected, and a mathematical model should be constructed to evaluate the drainage capacity and waterlogging risk of urban drainage system. Urban waterlogging risk levels should be divided into waterlogging safety zone, light danger zone, medium danger zone and high danger zone. Medium and high risk areas should avoid underground garages, underground shopping malls, underground station exits and other facilities or take special protective measures. Urban emergency management departments should formulate evacuation routes and means for people from low-risk areas to high-risk areas when floods occur.
2. Promote the construction of sponge cities.
Urban development makes the underlying surface of farmland, wasteland, depression, reservoir, etc., which used to seep or store water, become the impervious underlying surface of building roof, asphalt pavement, etc., which greatly increases the urban flood flow and peak flow and increases the risk of waterlogging. Promote the construction of sponge city and adopt a series of measures of infiltration, storage and drainage to minimize the impact of urban construction on the underlying surface.
3. Increase emergency measures for urban flood control.
School playgrounds, urban parks, green spaces, outdoor football fields and other facilities are designed to be lower than the ground for temporary storage of urban floods, which will be pumped to the drainage pipe network by pumps after the floods.
4. Urban flood control management system should be established.
Before it rains, the meteorological department will make a forecast, and it will fall to the ground to form surface runoff, which will take some time to converge to a certain depth. It is necessary to use this time to do a good job in real-time rainfall monitoring and disaster prevention prediction and alarm. Urban meteorological departments, hydrological departments, emergency management departments and operating departments of important public facilities such as schools, subway stations and large shopping malls shall establish information sharing and coordination command systems. Departments at all levels should formulate emergency plans for flood control and waterlogging prevention, and there should be a coordination mechanism in the plans.
5, should strengthen the construction and management of drainage pipe network.
Study the return period of rainwater pipe network, and whether the design return period can be adjusted and appropriately increased. Or according to the classification of urban waterlogging risk levels in urban flood control and waterlogging prevention planning, different standards are applicable. Strengthen the daily management of urban drainage pipe network to ensure that rainwater outlets, inspection wells and drainage pipes are not blocked and can function normally at critical moments.