Research On Rainfall Runoff Simulation And Flood Risk Zoning Based On Cellular Automata

In recent years,flood disasters have occurred frequently due to abnormal climate change,which has caused severe economic losses and casualties to human society.my country is one of the countries with the most frequent flood disasters.Flood prevention and disaster mitigation is a task highly valued by governments at all levels.Due to the problems of low flood control standards,low flooding capacity,and poor dike quality in my country's small and medium-sized rivers,river flooding often occurs during the flood season,which often threatens the production and life along the coast and causes serious flooding losses.Through systematic research on flood risk in river basins,decision-makers can have a comprehensive understanding of the temporal and spatial changes and risk levels of flood disasters in the study area,and scientifically and quickly formulate flood prevention and disaster mitigation strategies when floods arrive,minimizing flood disasters.Adverse effects.Flood risk refers to the possibility of losses and injuries caused by floods.The study of flood risk in a river basin can be divided into two aspects:one is the numerical simulation of floods,and the other is the study of flood risk zoning.Flood numerical simulation mainly simulates the process and development trend of flood disaster through numerical analysis.With the rapid development of computer technology,the models of flood numerical simulation are becoming more and more diverse.Existing flood numerical simulation research is mainly based on Saint-Venant's equations and momentum equations,which requires high data accuracy and completeness,and is complicated in modeling and takes a long time to solve.Its practicability needs to be studied.Flood risk zoning uses different risk levels to calibrate the study area according to the degree of flood damage.Macro-quantitatively describe the flood risk,which can intuitively display the spatial distribution of flood risk.In previous flood risk zoning studies,the selection of flood risk assessment indicators was relatively simple,and the zoning process was limited by the experience and cognitive level of decision makers,resulting in uncertainty in the calculation of indicator weights and affecting the zoning results.Aiming at the problem of flood disasters in mountain torrents of small watersheds,this paper takes the control watershed of Sihe College Station as the research area,constructs a cellular automaton(CA)model of watershed rainfall runoff,and focuses on innovating and expanding the rules of runoff and runoff in the model.The measured water level data of the academy station is used to rate and check the model parameters.The optimized model is used to simulate and analyze the evolution process of typical historical floods.ArcGIS is used to visualize the simulation results.Finally,the genetic analysis method and Monte Carlo are used.Auxiliary analytic hierarchy process was used to establish flood disaster risk zoning model,and combined with the results of flood simulation,the flood damage degree of the study area was graded.The main research contents and research results are as follows:(1)Based on the cellular automaton,the construction of watershed rainfall runoff model.In this paper,the principle,composition and applicability of cellular automata are systematically described,and the CA model of rainfall and runoff is established in conjunction with hydrological and hydraulic methods.Innovation and expansion,including detailed analysis of methods such as flow direction analysis of slope confluence and river confluence,calculation of flow velocity,and water distribution,and programming and development of the model in MATLAB software.(2)Simulation of rainfall and runoff in the study area.The two flood events in 1995 and 2001 were used as calibration and verification,respectively,and the key parameters in the model such as Manning coefficient and infiltration rate were calibrated and calibrated in combination with the measured water level data of Sihe College Station.Relative error,certainty coefficient and Nash efficiency coefficient are used to measure the fitting effect,and a set of optimal parameter combinations is obtained.The optimized model is used to simulate a typical historical flood in 2007,and the simulation results are visualized on GIS to obtain the inundation process map of the flood and the distribution of the maximum inundation depth and the maximum flood velocity.(3)Research on flood disaster risk zoning in small watersheds.Based on the simulation results of the rainfall and runoff CA model in the watershed,the flood evaluation indicators such as flood depth,flood velocity,topography,water system,land use type,socio-economic,population distribution,and basic transportation are fully considered in the study area to establish flood disasters.Risk zoning model,using Monte Carlo method and AHP to analyze and estimate the evaluation index weight value,using ArcGIS's map algebra tool to normalize each index data,and get the flood disaster risk zoning map of the Sihe Academy Station controlled watershed,according to The magnitude of the flood damage was divided into several risk levels by the natural breakpoint classification method,and the results of the zoning were analyzed.The research results have important reference value for flood control decision-making in Sihe River Basin.