Temporal And Spatial Variation Of Surface Water Resource And Flood Susceptibility Assessment In The Huaihe River Basin Using Multi-source Remote Sensing Data

The Huaihe River Basin is located at the natural dividing line between the north and the south of China.In recent years,under the influence of climate change and human activities,the surface water has changed dramatically in time and space,and the basin is vulnerable to floods.Frequent flood disasters have seriously threatened the lives of the people.and property safety.The Huaihe River merges into the Yangtze River through the Sanjiang Camp in Yangzhou.During the flood period,the amount of water in the upper reaches of the estuary has a significant impact on the water level and sediment content of the main stream of the Yangtze River.Therefore,it is more important to accurately and quickly monitor the flooded range during floods,explore the temporal and spatial variation of surface water and water turbidity in the basin,and evaluate the susceptibility of floods in the basin,which can improve the management of water resources in the basin and the monitoring and improvement of flood disasters.preventive ability.In this study,the Huaihe River Basin is taken as the research object.In view of the high requirements of accurate and time-efficient monitoring of the flooded area during flood disasters,a new method based on Synthetic Aperture Radar(SAR)texture information and Light Gradient Boosting Machine(Light GBM)was proposed for water extraction,which improves the accuracy and efficiency of water monitoring during floods.Based on the proposed new water body extraction method and global surface water dataset,the temporal and spatial changes of surface water in the Huaihe River Basin have been monitored for the past 40 years in a long-term time series,and high time-frequency monitoring has been carried out for the distribution changes of floods during the Huaihe River flood in 2020,and the surface water dynamics were obtained,and the water turbidity before and after the flood season was monitored,which can provide a reference for the water resources management to relevant departments.Based on the monitoring information of surface water bodies,the frequency ratio and logistic regression were further used to evaluate the flood susceptibility of the Huaihe River Basin and identify the disaster-prone areas,which provided a scientific basis for the formulation of disaster prevention and mitigation policies.The main contents and conclusions of this study are as follows:(1)Remote Sensing Research on Surface Water Extraction MethodsA new water body extraction method based on SAR image texture and Light GBM algorithm was proposed.Compared with the water body index method,SVM,RF and GBDT method,it shows that: in three typical areas of river area,lake area and flood submerged area,the extraction accuracy of this method is above 98%,which is better than other methods.At the same time,the operation efficiency of this method is 20-100 times higher than that of other methods,which greatly improves the timeliness of emergency monitoring of flooding information during flood disasters.(2)Analysis of temporal and spatial variation of surface water and research on remote sensing monitoringCombined with the proposed new water body extraction method and the global surface water dataset,remote sensing monitoring of the temporal and spatial changes of surface water at different temporal and spatial scales was carried out in the Huaihe River Basin,and the turbidity of Hongze Lake and Gaoyou Lake before and after the flood season was estimated.The results show that since the 21 st century,the area of permanent water bodies in the Huaihe River Basin has increased by about 28.27km2 per year on average,and the area of seasonal water bodies has decreased by about 37.26km2 per year on average.The high-value areas of water body frequency are concentrated in the center of large water bodies and the main stream of rivers,and the low-value areas are concentrated in the edges of large lakes and flood storage areas in the basin.The newly added seasonal water bodies in the middle reaches account for 9.12%,accounting for the largest proportion of all secondary water resources divisions.Newly built reservoirs,flood storage areas and rivers entering the sea have become new seasonal water bodies.Monitoring the floods in the Huoqiu-Yingshang section of the middle reaches of the Huaihe River in 2020 showed that: June 21 to July 27 was the process of flooding and submersion,July 27 to September 25 was the process of flooding and retreating,and the submerged area was on July 27.Reaches the maximum value.The turbidity of Hongze Lake and Gaoyou Lake after the flood season increased by 44.89%and 44.54% respectively compared with that before the flood season.During the period from 2016 to 2020,the turbidity from 2016 to 2018 decreased year by year,and reached the lowest level in 2018.(3)Susceptibility Assessment of the flood in the Huaihe River BasinBased on the rapid monitoring of the flooding information of flood disasters,the frequency ratio and logistic regression algorithms were used to construct the flood susceptibility evaluation model and evaluate its flood prediction performance,and obtained the flood susceptibility grade distribution map of the basin.The results show that the flood susceptibility assessment model based on logistic regression has better prediction performance and is more suitable for flood susceptibility assessment in the Huaihe River Basin.The extremely low,low,medium,high and extremely high risk areas in the Huaihe River Basin accounted for 55.91%,16.19%,11.12%,14.95% and1.84% of the total area of the basin respectively.The medium-risk and lower-risk areas are mainly distributed in the middle reaches of the Huaihe River and the Yishusi River,and the high-risk and extremely high-risk areas are mainly distributed in the middle and lower reaches of the Huaihe River.The high-risk and extremely high-risk areas are mainly distributed in the main stream of the Huaihe River,the middle and lower reaches of the major tributaries,and the areas near major lakes.In summary,this study extracted surface water bodies in the Huaihe River Basin based on multi-source remote sensing data,analyzed the distribution and changes of surface water and turbidity information,and evaluated the flood susceptibility of the basin based on the monitoring information of surface water bodies.The results can provide a reference for the sustainable development of surface water resources in the Huaihe River Basin and the prevention and monitoring of flood disasters.