Study On Urbanization Development And Its Influence On Rainstorm And Flood Risk In Nanchang City

In the context of accelerated global urbanization and climate change,the natural hydrological cycle has been severely disrupted and destroyed.When there is a strong rainfall and insufficient drainage capacity of drainage pipes,it often leads to serious flood risk problems in urban areas.In order to study the impact of urbanization on the risk of storms and floods,this article firstly analyzes the characteristics of Nanchang’s urbanization development from three aspects:economy,land and population based on the economic data of Nanchang from 1994 to 2014.The urbanization level score is used as the basis for the division of urbanization stages to divide the urbanization development stages of Nanchang City,and select lighting data to verify the division stages;secondly,based on the daily rainfall data of Nanchang City from 1965 to 2015,extract After the threshold value,linear tendency rate,moving average method,Mann-Kendall non-parametric test method,wavelet period method,improved Mann-kendall mutation test method,etc.are used to analyze the change characteristics of extreme rainfall in the process of urbanization from both time and space.Calculated the temporal and spatial trends of urbanization’s contribution rate;finally,based on the disaster risk theory,different stages were constructed from four aspects:the sensitivity of the hazard environment,the risk of hazards,the vulnerability of the hazard-bearing body,and the ability of disaster prevention and mitigation.Zoning model of storm and flood risk.The main conclusions are as follows:(1)From the perspectives of population,land,and economy,the urbanization level of Nanchang City is showing an overall upward trend;among them,the period of rapid population urbanization growth is from 1999 to 2006,and the rapid growth rate of land urbanization The time period is from 2000 to 2005,and the period of rapid economic urbanization growth is from 2003 to 2010;in general,the urbanization level increases faster during the period from 2000 to 2005.From the districts to Xinjian County and Nanchang The counties and Qingshan Lake District have a faster growth rate.The Qingyunpu District,Xihu District and Donghu District have higher starting points,and the slower ones are Anyi County,Jinxian County and Wanli District.According to the urbanization development score,2002 was designated as an urban highway The stage of development is divided into points,and the division is considered reasonable after lighting verification.(2)In terms of time,the number of rainstorm and heavy rainstorm days in the year showed a trend of first increasing and then decreasing,and the most distributed month was June;the average daily heavy rain and heavy rainstorm were distributed in May to September and June to September respectively;The number of inter-annual rainstorms,heavy rainstorm days and the average single-day heavy rain and heavy rainstorms all showed an increasing trend.The abrupt years were 1992,2013,2005,2009 and 2012,and there were relatively high frequencies at 3,2,2,and 2 frequencies.Obvious cycles,in which the number of torrential rain days are 32 years,18 years and 8 years,the average single-day heavy rainfall is 32 years,8 years,the number of heavy rainstorm days and the average single-day heavy rainfall are 19 years,8 years.Spatially,the number of heavy rains is high in the northwest and southeast,and low in the middle;heavy rains decrease from northwest to southeast;average daily heavy rains are higher in the northwest and lower southeast;average heavy rains per day decrease from southeast to northwest.(3)The impact of urbanization on extreme rainfall has certain differences in temporal and spatial distribution.The contribution of urbanization to the number of rainstorm days shows a decreasing trend in the northwest,southeast and central regions for many years,and an increasing trend in other regions;The average single-day heavy rain rainfall is a multi-year decrease trend in the northwest and southeast,and an increase trend in other regions;the number of heavy rain rainfall days is a multi-year decrease trend in the central region and a multi-year increase trend in the surrounding areas;the average single-day heavy rainfall is a multi-year increase trend in the north and a multi-year decrease trend in the south.(4)The economic data has been refined by constructing the GDP spatial distribution model and population density spatial distribution model in the vulnerability of disaster-bearing bodies.It has been verified that the relative error is basically less than 0.05,and the model is more reasonable.From the comprehensive evaluation results of the sensitivity of the hazard environment,the hazard risk,the vulnerability of the hazard-bearing body,and the disaster prevention and mitigation capabilities,it can be seen that the hazard environment sensitivity,hazard risk,The area of the medium and high-level areas for the vulnerability of the bearing body and disaster prevention and mitigation capacity are 6224.54km~2,5654.83km2,277.75km~2and 4257.38km~2,accounting for 87.89%,78.69%,3.87%and 59.86%of the total area respectively;the rapid development stage of urbanization The area of medium and high-grade areas with hazard-pregnancy environmental sensitivity and hazard risk factors have been reduced,respectively,5130.13km~2and 3439.15km~2,accounting for 72.45%and 47.86%;medium and high-grade areas with carrier vulnerability have increased,Which is 4111.53km~2,accounting for57.24%.The areas with high disaster prevention and mitigation capabilities have increased,mainly in the middle of the city.(5)The area of heavy rain and flood risk zoning is about 463.83 km~2in the middle and low-speed development stage of urbanization,and about 311.65 km~2in the high-speed development stage.In addition,the medium-and second-high-risk areas in the middle and low-speed development stage of urbanization are developing at a high speed.The stage level is reduced and the area is reduced,and the overall risk level is reduced.Among them,the northeastern part of Xinjian County is due to the reduced risk of hazard factors;Xinjian County and Nanchang County’s central area is due to the reduced sensitivity of the disaster-pregnant environment;the central part of Xinjian County is due to the improvement of disaster prevention and mitigation capabilities and the reduction of hazard factors;The western part of Anyi County and the northeastern part of Jinxian County are due to the reduced risk of hazards;the central part of Nanchang City is due to the improvement of disaster prevention and mitigation capabilities.In addition,a small number of areas have increased risk,mainly due to increased vulnerability of the area.