1 Current situation of urban flood control and drainage
At present, there are many bad weather, and many cities become waterlogged as soon as they encounter heavy rain, so they can "see the sea" everywhere. With the deterioration of the environment, waterlogging has occurred in many areas of our country, and the phenomenon of waterlogging has become more and more serious and spread more and more widely, which has caused harm to people's travel and life. Because people destroy the ecology, cause air pollution, make the rainstorm worse and worse, and pollute the rivers. Due to the backward development of flood control facilities, the drainage technology can not be well developed, and the rainfall is increasing, many cities have become waterlogged cities when they encounter heavy rain, and the phenomenon of rising water has appeared everywhere, resulting in the phenomenon that the sea can be seen everywhere. Flooding also damaged the facilities of the city. Many people can't travel normally, which leads to traffic congestion and frequent traffic accidents, posing a threat to the safety of the whole city. Because the rainstorm contains acid rain, the road surface is eroded by acid rain, causing ecological problems. Therefore, people's health is also harmful, and because they can't work normally, it also poses a threat to urban economic development. The emergence of ecological problems is not conducive to the environmental development of the city objectively, but also inhibits the cultural development of the city objectively. At the same time, the occurrence of waterlogging makes people panic, which is not conducive to the stable development of society. Generally speaking, the situation of urban drainage is grim, and waterlogging has become an obstacle to urban development. The government should strengthen rectification measures to ensure the long-term, healthy and reasonable development of the country.
2 Causes of water accumulation
2. 1 The flood control standard is too low, and the river channel storage capacity is insufficient.
Flood control standards are too low, resulting in waterlogging. The government did not formulate reasonable flood control standards, which led to problems in the rainstorm control system. It is impossible to formulate specific flood control and drainage measures through correct standards. Because the standard is too low, the corresponding preventive measures are unscientific when the rainstorm is too heavy, and the data standard is set too low. When the actual data is greater than the standard data, reasonable measures are not taken, resulting in waterlogging and destroying the environment. At the same time, the government's ability to regulate and store rivers is not enough, and rivers are not well regulated. When the rainstorm is too heavy, the water level rises too fast, which makes the water volume expand outward and does not control the water level reasonably. The construction of river banks does not conform to the development of regulation and storage, which causes the road surface and river banks to be eroded by rain, and the rain spreads to other places, even to the city center, causing waterlogging and endangering the environment.
2.2 The design is unscientific and does not adapt to the current flood control situation.
The design scheme of flood control and drainage is unscientific and is the focus of waterlogging. In urban areas where waterlogging often occurs, appropriate schemes to control waterlogging should be set in advance. Only in this way can we choose the most suitable drainage technology and solve the frequent waterlogging problem. However, judging from the current situation in many urban areas, the relevant design of flood control and drainage can not adapt to the waterlogging state in urban areas, so it is difficult to highlight the actual effect within the drainage level. The relevant personnel failed to check the existing waterlogging state of the city, and prepared a suitable scheme according to the values obtained from the inspection. In this case, it is difficult to set the relevant mechanism in advance and prepare the control mechanism.
2.3 The people's awareness of disaster prevention is weak, the government's propaganda is insufficient, and the preventive measures are unreasonable.
People's weak awareness of disaster prevention also led to waterlogging. The masses have no awareness of disaster prevention, do not have a thorough understanding of disasters, and do not strengthen prevention, resulting in the inability to take scientific preventive measures when there are signs of disasters. At the same time, government officials did not carry out relevant disaster prevention propaganda, nor did they put forward corresponding solutions to the specific problems of disasters. As a result, the masses are often helpless in the face of disasters. Moreover, due to the lack of publicity by government personnel, many people have a vague impression of the disaster and do not understand the harm caused by waterlogging, which makes the overall level of disaster prevention and control low. Preventive measures are unscientific, and correct measures are not taken for specific disasters. Before the flood, there was no relevant flood prevention early warning, no reasonable and scientific monitoring to minimize the harm, no scientific early warning on when the harm was easy to occur and where the harm was greatest, which led to the people in the affected areas not being resettled in a safe place in time, not strengthening flood prevention and rectification, and not taking relevant preventive measures for the relevant river banks and coastal waterlogging areas, resulting in frequent waterlogging disasters and no improvement.
3. Adjust the design and propose solutions.
3. 1 Accepting appropriate standards
The existing flood control standards are determined according to the divided urban grades and the importance of urban areas. It can be inferred from such standards that the available flood control standards selected by cities are closely related to the existing population in urban areas. However, you can preset the plan according to the shape of the river in the case of zoning. This zoning fortification can protect the urban population less than the total population, and cities can choose various preset standards. Therefore, if we want to apply the existing default standards, we should consider the partition or the overall situation.
3.2 Confirm the elevation of dike top.
For urban dikes with high water level, if the calculated superelevation value is less than two meters, the design should follow the value of two meters. In the urban area in the estuary section, or in the urban area with low wind speed, in the process of determining the elevation of the dike top, the existing standard should be slightly higher. If the urban area contains relatively high wind speed, or the urban area is located in the inland mountainous area, you can follow the usual specifications. In order to reduce the original funds, when the existing superelevation value does not exceed two meters, it should be set to two meters; You can also design a wave wall about one meter at the top of the original dike. For urban areas with low wind speed, we should determine the available superelevation value according to the calculated value.
3.3 Default self-discharge and pumping standards
(1) Select the self-discharge standard suitable for urban areas. Various tributaries involved in drainage have different topography, and the existing outlet elevations are difficult to be consistent. However, the overall design of self-drainage is to set appropriate prevention gates at the outlets of these tributaries and related dikes. The designed orifice size will not affect the overall engineering quantity. Therefore, the preset self-discharge standard should not be less than the maximum rainstorm actually measured in this dike. In the drainage area, there will be a default category that cannot be submerged. According to this category, as well as the existing volume of the storage area and the existing hardening situation of the drainage area, the available self-discharge capacity needs to be calculated.
(2) Select evacuation standards suitable for urban areas. The design pumping standard will be related to the existing pumping capacity and the existing installed capacity. The larger these two quantities, the more preset inputs. The rules for the design and use of pumping stations show that it is unscientific to choose 10 as the return period after the completion of the drainage area. This is because there is a difference between the elevation of each tributary used for pumping and drainage and the outlet. In order to design an accurate drainage standard, we should consider the tributary state contained in the drainage area and the elevation contained in the outlet. At the same time, it also takes into account the unique drainage frequency that urban areas will encounter under the same rain and flood conditions.
For diverse urban areas, there are many tributaries and basins; If we want to calculate such frequency arrangements one by one, it will consume a lot of labor. Under normal circumstances, we can infer the general process of water level rising after sluice closure according to the existing closed water level in the basin, so as to calculate the available rainstorm. Then, according to the existing rainstorm, the category that a given drainage area can't be flooded, the hardening of the surface, etc. , calculate the drainage flow contained in each basin. In this way, the safety of pumping station drainage can be maintained, although the necessary calculation will be expanded.
4 summary
With the continuous development of the city, the problem of disaster prevention and waterlogging prevention is becoming more and more serious. If reasonable measures are not taken to control it, the development of the city will be slow and bring a series of problems. Therefore, it is necessary to improve the technical level and strengthen the supervision mechanism to reduce disasters, promote the development of ecology and environment, promote the healthy development of more fields, and promote the political, economic, cultural and environmental development of the country.
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