Flood Discharge Capacity And Risk Assessment Of The Main Channel Of Chaobai River In Beijing

In recent years,Beijing has been affected by global climate change,and extreme weather has occurred every year,resulting in frequent short-term local rainstorms.At the same time,with the rapid development of the social economy of the lower reaches of the reservoir and river banks,especially the construction of new cities and towns in the suburbs The conditions of the underlying surface of the flood have been changed,and the flood peak and peak time of the flood have changed significantly.These factors have put forward new and higher requirements for the reservoir scheduling decision,and the frequency and scale of the reservoir’s flood discharge have increased.For the Miyun Reservoir and its downstream Chaobai River channel,due to its climate,engineering indicators and parameters of the reservoir and channel,and socio-economic changes,it has had a greater impact on the flood discharge safety and flood discharge capacity of the channel.At present,there has not been a systematic comprehensive evaluation and analysis of the flood discharge capacity of the changed rivers,and flood control scheduling decisions are facing great pressure and troubles.Therefore,it is of great academic value and practical significance to evaluate and analyze the flood discharge capacity of the lower reaches of Miyun Reservoir.The research content and results of this article are as follows:(1)For the downstream channel of Miyun Reservoir in the Chaobai River Basin,the flood evolution one-dimensional channel hydrodynamic model and coupled with the surface two-dimensional model are used to simulate the calculation of floods of different magnitudes in the basin,and the statistical analysis of the different sections according to the results of the simulation calculation The maximum flood discharge capacity of the river channel in the key flood protection areas and the maximum flood discharge capacity of the study section were analyzed,and a risk analysis was conducted on the inundation of the two banks of the channel under super-standard flood conditions.(2)In this paper,the calculation and analysis of the static Manning formula and the coupling model are used to calculate the overall channel water level and flow under different simulation schemes,which ensures that the maximum flow capacity of the single-point section on the channel does not exceed its embankment elevation.To ensure the safety of people’s lives and property on both sides of the downstream river channel,and also to ensure a safe discharge of Miyun Reservoir in the system during the process of dispatch and discharge.(3)In this paper,the flood discharge capacity is analyzed through model calculation combined with the scheduling plan:the designed minimum discharge flow of Miyun Reservoir is 600m3/s,and the calculated maximum discharge flow of the Baihe River in the two downstream channels of Miyun Reservoir is 33.6 m~3/s.The maximum flood discharge flow is 603 m~3/s,and it can be known by superposition that the designed minimum discharge discharge flow value that can achieve the actual safe discharge flow of the reservoir can be achieved.However,in practical engineering applications,it is also necessary to rectify the embankment or gate dam of the bayonet section of the key flood protection zone,and adopt corresponding engineering or non-engineering measures to improve the flood control capacity of the risk area.(4)When a 100-year design flood or even greater than standard flood occurs in the watershed,the dangerous section of the Gulou Street residential area at the downstream of the Chaohe River channel will be the first to have a dike and its impact range is easy to go south along the highway line to The spread of the Beijing-Chengdu Railway has caused huge risks to the residential areas,agricultural land,railways and main roads downstream;followed by the Caijiawa dangerous section of the Chaobai River,the Xiangyang gate dangerous section and the Henan village gate upstream dangerous section and other areas.The dikes have different degrees of flooding and flooding.Analyze the distribution,scope and evolution route of flood water depth in key flood protection areas in different periods,and use this as a basis to superimpose different social and economic factors to statistically analyze the risks caused by the inundation.According to the corresponding statistical analysis,when the river channel is exposed to excessive flood risk,the flooding risk is the greatest in Shunyi District.The residential area affected is 5.683km~2,the farmland area is 4497.12hm~2,and the length of the submerged railway and highway are 2.416km and 2.46km respectively.148.703km,and the flood with more than 1m has the widest impact and the greatest risk.