Flood Prevention and Drainage Literature in Zhuji City
â€”â€”Research on hydrological calculation and safety system
According to geographical terms, Zhuji City is located inland in central Zhejiang Province, belongs to the subtropical monsoon climate zone, has four distinct seasons, and has more rainwater. It is a typical hilly climate feature. The average annual precipitation is about 1373.6 millimeters , and the distribution is extremely uneven. It has the conditions for floods and floods. Therefore, flood prevention work should be done actively. In recent years, with the continuous development of Zhuji's urbanization and continuous economic development, the development of new urban areas is imperative. The development of the new urban area is slowly extending to those with low requirements for flood control and drainage, while the original flood control and drainage performance of the old city is not high. With the continuous expansion of new urban areas, the old city area is more susceptible to internal pollution. On the other hand, the urban space now presents a three-dimensional sense, which brings new challenges to flood prevention and drainage to a certain extent.
I. Analysis of the Causes of Flood-prone Disasters in Cities
1.1 Affected by Natural Factors
Changes in precipitation in Zhuji each year are bimodal, with great fluctuations. During the period from March to June and September, it is a rainy period. The precipitation averages about 158.3 days per year . Local weather resources are abundant, and floods and other disasters frequently occur. . Some areas along the river will cause excessive pressure on the drainage system due to excessive heightening of the river water, eventually leading to flood disasters; in addition, other regions are affected by heavy rain, and their strength may even exceed the original drainage capacity. Flood disasters. Regardless of the angle from which they are investigated, these abnormal climates will lead to heavy rain for a long time, and this will directly lead to urban hustle and bustle.
1.2 Affected by human factors
In fact, unreasonable and unscientific production and labor of the local residents will, to a certain extent, cause frequent floods in the city. Although natural factors directly lead to floods, the main cause is human influence. Due to the rapid economic development and the expansion of the population, forests and lakes were used to seize the right to use the land and indiscriminate cutting, destroying the vegetation in the entire region, and forcibly filling lakes and rivers, so that the flood discharge channels were continuously narrowed. The siltation of rivers, which in turn causes the destruction of the entire natural ecological structure, flood discharge is not smooth, and flooding occurs more frequently. In the process of developing cities, the flood disaster caused by human factors may be due to the following reasons: 1 The site selection for urban expansion is not appropriate; 2 The flood control requirements set are not high; 9 Man-made flood protection facilities are destroyed (4) Inadequate flood control management; (5) Excessive use of flood passages during the construction of cities, which prevented the timely discharge of floods; (6) destroyed natural urban water systems; (7) excessive use of groundwater resources, which caused gradual ground settlement.
1.3 Influenced by Urbanization Expansion and Development
The continuous expansion of towns and cities has changed the original natural features of the area. Slowly, urbanization has continued to expand and expand. The area of â€‹â€‹crops and trees has gradually become smaller, followed by a variety of industrial areas, commercial and residential buildings, and residential buildings. In some cities there is a lot of impenetrable water that covers the surface of the depression where water accumulates. It is because of the original permeable vegetation and the large area of â€‹â€‹the soil that is impregnated with high strength, causing a certain degree of infiltration phenomenon and a significant reduction in the evaporation rate, and the rate of its flow is also accelerating, and the amount of its runoff. Also increasing with it, the final result is the advance of the peak time. At the same time, the local infiltration volume will decrease at one side, which will result in a corresponding decrease in the supply of certain groundwater. In the drought period, the basic flow of rivers is bound to decrease accordingly.
II. Introduction to the calculation model of urban flood control and drainage in hydrology and water conservancy
The calculation of hydrology and water in cities is mainly based on the random nature of hydrological phenomena. Using the principles and methods of probability theory and mathematical statistics, the statistical characteristics of hydrological data are used to estimate the hydrological eigenvalues â€‹â€‹of a given design frequency. In general, there are few samples based on hydrological statistics methods, and the sampling errors are relatively large, which often cannot meet the production needs. Therefore, it is not possible to perform calculations based solely on the hydrological data at the site where the project is located. It is also necessary to perform a full rationality analysis of the calculation process and the calculation results in order to obtain the design hydrological data of the project site more reliably. The following briefly introduces three types of hydrological and hydraulic calculations:
2.1 Assumed Rainstorm Calculation
With the advent of heavy rains, flooding may occur. In regions where flood data are scarce, floods can be indirectly estimated and calculated through heavy rainfall. This is one of the most commonly used calculation methods, and it is precisely because such a rainstorm design can be said to be an extremely important link in the design of flood calculation accuracy. Because the conditions for the appearance of various heavy rainstorms are not the same, and the terrain in raining areas is also very different. Therefore, the method for calculating the spatial and temporal distribution of these heavy rainstorms is also a variety of forms. There is no relatively fixed pattern to carry out. . Usually, it is used to calculate the historical data of an area, to obtain the average tense after inquiring the related storm data, or to select a relatively poor combination, and to use it as a design basis for the spatial and temporal distribution of heavy rain. Today's hydrological calculations mostly assume the same frequency of rainfall and floods at that time. It is reasonable to determine whether the heavy rain design calculations are reasonable. To a large extent, it depends on the selection of heavy rain samples and the data review of samples and how to select frequencies. Curves and so on.
2.2 Calculation of production flow
The production stream mentioned here refers to the process of generating and integrating the different runoff components in each basin. In terms of popularization, when the water is in vertical operation, it is affected by various comprehensive factors, and the same is the redistribution of precipitation. The amount of a process. Different conditions of the underlying surface will have different flow mechanisms, and the differences in the production flow mechanism will affect the development process of the entire production flow, and there will be some different characteristics of runoff. For example, in rural areas, most of them are based on the natural underlying surface. Nowadays, the exploration conditions for the flow mechanism of the natural underlying surface in the world have matured, but the area of â€‹â€‹the city's underlying surface is relatively complex. The study of the mechanism's production flow is also relatively small. Therefore, the calculation of the production flow model adopted according to the different production flow mechanisms must also be based on local conditions.
2.3 Convergence calculation model
It usually follows the law of the distribution of clean water in the recent rainfall in this basin, and derives the changes in the amount of runoff from the inlet and outlet faults. There are many ways to calculate the confluence, which can be divided into two kinds of non-linear and linear confluence models according to the drainage relationship of the basin. According to the distribution of the input space, two kinds of parameters can be distinguished: the parameters of the lumped distribution. Under normal circumstances, the urban confluence values â€‹â€‹are calculated from the confluence of slopes and the confluence of river networks.
June 2011, Zhuji City, the largest Mei Yuhong water occurred since 1997, in the flood, Zhuji City, hydrological station crew by the division of work, do a good job uninterrupted flow tests, site maintenance, shot regimen message Report Such as key work to ensure the timely and accurate reporting of water status data, to provide decision-making basis for flood control. After the flood, the municipal hydrology station carried out the â€œ 6 Â· 16 â€ storm flood investigation in Puyang River in time according to the hydrological flood investigation criteria, conducted on-site investigation and analysis through on-site investigation of flood traces, visits to local residents, field surveys, etc. to collect and grasp this The characteristics of the floods provide scientific data for analysis and summary work.
Third, build a corresponding security system model for flood prevention and drainage measures
In the floods in June last year , Zhuji became one of the worst-hit counties ( cities ) in the province . After the floods , the city â€‹â€‹painstakingly and painstakingly proposed to speed up post-disaster reconstruction and vigorously implement the three-year construction plan for water conservancy facilities . July 23, the municipal government issued The implementation opinions on accelerating the reform and development of water conservancy and clarifying the future water conservancy construction target measures . September 14, issued by the municipal government to develop a three-year water development in Zhuji City building programs to further accelerate the pace of construction, water conservancy construction in the next three years to implement the task. In the next three years , the city plans to allocate a total project investment of 607.3 billion yuan , of which 3 years plan to invest 422.4 billion yuan , the first annual plan to invest 142.4 billion yuan , the second annual plan to invest 143 billion yuan , and the third year plans to invest 42 billion yuan . The government has issued a series of plans and opinions to provide policy support for the construction of a flood protection system.
The so-called safety guarantee refers to the use of certain effective means to ensure the safety of life, property, and food sources. The safety and security system of a city in flood prevention and drainage is mainly to say that the society responds to the ideal strategy for certain flood disasters that need to be faced in a specific area or historical period of the city. This requires a proper scientific and comprehensive analysis of floods and disasters, and then discriminates and finally predicts. Based on this, through engineering and non-engineering, publicity, and other activities, we will step up the cityâ€™s ability to defend against floods and disasters. The risk of natural disasters falls within an acceptable and manageable range, and it is expected to achieve the vision of a comprehensive and sustainable society.
In order to allow the security level of cities in flood control and flood discharge to correlate with the increasing safety of natural disasters, we must build a safety system that is suitable for the flood situation of the city from all angles and all aspects, so that the risk of flood disasters can be controlled by people. Within an acceptable range, this can ensure the sustainable development of the economy. From a risk management point of view, the construction of a city's all-round flood protection and drainage safety system needs to follow eight principles:
The first is to reduce the risk caused by floods and floods; the second is to be able to avoid the risks caused by floods; the third is to share the risks caused by disasters; the fourth is to increase the capacity to resist disasters in a timely manner; The fifth is to increase the capacity for temporary disasters; the sixth is to avoid some man-made disasters; the seventh is to strengthen the ability of disaster warning; the last point is to strengthen the ability to respond to disasters.
To sum up, the safety and security system is actually a complex and comprehensive system. Especially for urbanization construction, it can not only play the role of general flood control and flood protection, but also integrate many factors affecting urbanization. Unfortunately, although the theory of hydrology and water conservancy has entered a mature track, there are few studies on the foundation of the calculation results to study the safety and security system of flood prevention and drainage. From this, we can see that more efforts should be made in security research in the future.
This article comes from the Internet, edited and edited by China Rescue Equipment Network.
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