Study On Flood Conveyance Capacity Of Rivers In Small And Medium Basins Without Hydrological Station

At present,many small and medium-sized rivers are confronted with serious flood disasters during the flood season.The affected area caused by flood disasters of small and medium-sized rivers has an increasing trend year by year,and the disasters have caused huge losses to people’s lives and property,which has become one of the most urgent problems to be solved in China.At the same time,there are many small and medium-sized rivers in China.Most of these rivers are also called small and medium-sized rivers without data due to the lack of hydrological stations.However,due to the lack of hydrometeorological data,it is difficult to do researches on the flood conveyance capacity of these rivers,which makes it impossible to carry out effective flood control management of these rivers.Passive flood control measures can only be taken when floods occur.The lower reaches of Ying River Reservoir flow through important towns such as Daying Town,Wulu Town and Heidao Town,as well as important villages such as Xuying Village and Caijia Village.The downstream basin of Yingna River Reservoir is a typical small and medium-sized basin without data in Liaoning Province,which has not only restricted the development of downstream economy,but also posed a serious threat to the safety of people’s lives and property.Therefore,this paper chooses the downstream channel of Yingna River Reservoir as the research object to do the flood conveyance capacity analysis.This paper firstly calculates the design rainstorm in the basin,then calculates the design flood by using different design flood calculation methods without data.After comparing and analyzing the calculation results,the calculation method which is more suitable for the watershed is determined and the design flood is calculated by this method.On this basis,after the construction of one-dimensional hydrodynamic model for the downstream channel of Yingna River Reservoir,this paper carried out a study on flood conveyance capacity and put forward suggestions for flood control of the river.The main contents and achievements of this paper are as follows:(1)There are no hydrological stations in the downstream watershed of Yingna River Reservoir and no measured hydrological data are available.Therefore,based on the characteristics of Yingna River Basin and the related data of historical flood disasters,the characteristics of rainstorm and flood disasters and historical flood information in the watershed are studied.After calculating the design rainstorm in the basin by using the calculation method in Calculation Method of Designed Rainstorm Flood for Small and Medium-sized Rivers(areas without data)in Liaoning Province,the design flood in the downstream basin of Yingna River Reservoir is calculated by Liaoning Province calculation method and American Engineering Manual calculation method respectively.After comparing the results of design flood,it is found that although the calculation method of American Engineering Manual will be updated according to the latest research results and hydrological data,it has greater subjectivity in judging the parameters,which results in greater randomness of the calculation results.The division of hydrological zones in the calculation method of Liaoning Province can ensure the objectivity of the calculation results,and the calculation results can better reflect the flood characteristics of the watershed.Therefore,the design flood process once in 10 years and once in 20 years is calculated by Liaoning Province calculation method in this paper.(2)One-dimensional hydrodynamic model is constructed by using the measured data of river section downstream of Yingna River Reservoir.After the model is built,the parameters of the model are calibrated by using the collected historical flood data.Considering the most likely combinations of floods and tides,the combination of design flood once in 10 years and design high tide level once in 20 years and the combination of design flood once in 20 years and average high tide level for many years are input into the model for calculation,and the simulated water surface line is obtained as the criterion to judge the flood conveyance capacity of the downstream river of Yingna River Reservoir.Based on the model,the influence of tidal jacking at the Yingna River estuary on the flood conveyance capacity of the river is quantified to a certain extent by simulation calculation.After determining the guaranteed and warning water levels of the river and combining with the simulated water surface curve,the flood conveyance capacity of the lower reaches of Yingna River Reservoir is determined in this paper.(3)For the safety of people’s life and property,this paper identifies the sections with weak flood conveyance capacity in the downstream channel of Yingna River Reservoir.For the safety of flood control and management,five observation points of flood control characteristic water level are determined in the downstream channel of Yingna River Reservoir,and suggestions for flood control are put forward accordingly.In this paper,the suggestion for flood discharge of Yingna River Reservoir is put forward for the safety of Caijia Village,the most vulnerable to floods place in the downstream basin of Yingna River Reservoir.Finally,this paper analyses the reasons why the flood conveyance capacity of the downstream channel of Yingna River Reservoir does not meet the requirements,and puts forward some suggestions for improvement.