Flood Simulation And Impact Assessment Under Future Urban Sprawl In Jinan City

In recent years,the world economy has entered a period of rapid development,and the urban area has grown rapidly.When the city is facing high-intensity rainfall,the frequency of flooding occurs due to the hardening of urban roads and the old and damaged drainage networks high.The urban area of Jinan continues to grow,and due to its special topography,it will induce more serious rain and flood disasters,bringing serious economic and property losses to the Jinan municipal government and people.Especially in 2007,the rain flood was the most serious in 0718.This paper takes the urban area of Jinan as the research object,based on the cellular automata theory,selects the SLEUTH simulation software to establish the prediction model of the urban dynamic growth of the study area;the Caflood two-dimensional rain flood simulation software is used to establish the simulation model of the urban rainwater in the study area,and the combination of the two predicts the simulation of rain and flood in the future growth of Jinan city.The dynamic growth process of urban area in Jinan City from 2019 to 2035 was completed,and the Caflood model was established and verified.Based on the simulation results of the two,the comprehensive analysis and evaluation of the scenes in the basin from 2035 to the rain and flood in the city will be carried out.The main conclusions are as follows:(1)Cellular Automata(CA)Theory The "bottom-up" calculation concept is applicable to urban area dynamic growth simulation and rain flood simulation.The SLEUTH model can effectively combine 3S technology and the CA algorithm is simple and transparent;the Calalod model uses cells.Automated machine(CA)technology replaces the traditional shallow water wave equation solution,which greatly improves the calculation efficiency.(2)The SLEUTH model is used to predict the dynamic growth of urban area in Jinan City from 2019 to 2035.Firstly,based on the data collection and processing,the data set required by the model is organized,and then the calibration process is completed by the rough calibration,fine calibration and final calibration.The calibration results are better.The spatial growth simulation analysis is carried out on the historical year of the study area.Compared with the real development trend of the urban area,it can show the theme growth of Jinan City,indicating that the SLEUTH model has good applicability to Jinan City and can be used for the future growth forecast of Jinan City.(3)On the basis of the calibration results of the SLEUTH model,three different urban development scenarios are established according to different land use type predictions: free growth,basic protection and strict protection.The results show that the urban area of Jinan is still in a growing state in the future,and the growth rate is decreasing continuously.With the increasing protection probability for various types of land,the growth area is decreasing,and the growth coefficient changes under the three scenarios.The trend is roughly the same,and the spread coefficient is dominant,and the effect of reproduction and road gravity is supplemented.The three scenarios are in line with Jinan’s "Control the south,Go west,Expand eastward,Optimize the middle" planning policies.The prediction results can verify the accuracy of the SLEUTH model and provide a theoretical basis for Jinan urban planning.(4)This paper analyzes the causes of heavy rain flood disasters in Jinan City and establishes a two-dimensional rain flood flooding simulation model of Caflood.The model is selected for the typical storm floods in 8 cities.The relative error of each index is smaller.The larger error is mainly determined by several abnormal points.However,the simulated water depth is consistent with the measured maximum submerged water depth.Each parameter satisfies the model accuracy requirements and is suitable for further simulation analysis.(5)Based on the Caflood model,the "20070718" flood was simulated,and the simulation results were visualized.The DEM data files with different precisions were used for calculation and compared with the MIKE21 calculation results to verify the speed and accuracy of the model.The visual simulation results are basically in line with the actual situation.The key water-storage areas in the central and northern regions,the heroic mountain road,the Jianshe Road,the Yuhua Road,the Second Ring Road and other roads all have road flooding,which confirms the flooding of the South China Sea after the rainstorm in Jinan.The numerical calculation results show that 22 measured points are selected,and the maximum water depth error of the Caflood simulation with the 10 m resolution DEM as the model input is 0.21 m,and the average error of the 30 m simulation is 0.33 m,but the 30 m resolution DEM runs.The time is only 1/15 of the DEM of 10 m resolution.The average error of the MIKE21 simulation is 0.27 m.The results show that the model is reliable,accurate and can reflect the motion characteristics of floods.Compared with other distributed rain flood models,it has better calculation time,lower modeling conditions and better adaptability.Urban flood warning and emergency plan.(6)Based on the growth of urban area in Jinan City based on the SLEUTH model from 2018 to 2035,combined with the Calaflood model,the temporal and spatial distribution of urban rainwater floods under future scenarios is predicted.The future state of the urban area predicted by the 2035 under the basic protection scenario is selected to simulate the rain and flood of urban growth.The rain type scheme selects two actual rain patterns of 0718 and 0826 and design rain patterns for 3 hours and 24 hours.Based on this,the rain type simulation analysis of different scenarios in the future is carried out.The simulation results show that the return period of short-lived heavy rainfall reaches 50 years.In the future,the distribution of locusts in Jinan urban area is relatively stable,and the area growth rate is small,but the maximum water depth becomes larger;the flood damage caused by long-term heavy rainfall is more serious;the "20070718" rain type is taken as an example to predict the simulated flooding situation in 2035.It is basically similar to the 2007 flooding scenario,but the peak of flooding depth is advanced in 2035,the area of high-risk area is increased,and the flood risk risk map shows that the "South-water flooding" scenario is more serious after the 2035 storm.The results of the study reflect to some extent the impact of urban growth on flood submersion.