Hundred-year-scale Sudden Flood Simulation In The Lower Reaches Of The Syr River Based On HEC-RAS

Flooding is one of the most common extreme hydrological events.Flood disasters will cause varying degrees of damage to farmland and cities,and even threaten the safety of life and property.Forecasting flooding in advance can reduce the damage of floods to a certain extent.In this study,the lower reaches of the Syr River in the Aral Sea Basin in central Asia were used as the research object,and the digital elevation model(DEM)with a resolution of 30 m × 30 m was used as the data source.With the help of the ArcGIS platform,the boundary of the lower Syr River Basin was extracted to digitize the Syr River In the lower reaches of specific rivers,extract the hydrological elements such as the channel center line,riparian line,flood area and cross section;statistically analyze the monthly flow data from 1935 to 1985 and the precipitation data of 22 meteorological stations over the past 100 years,using rain-The flood-related method and the flow data empirical frequency method are used to design floods,and the flood peak flow values at the frequency of once every 20 years,once every 100 years,and once every 1,000 years are derived.With the help of the river analysis system(HEC-RAS)hydraulic model,the flooding simulation study of the lower reaches of the Syr River was carried out.The main findings are as follows:(1)The flow data monitored by the three hydrological stations(Tomenaryq Station,Karaozek Station and Kazalinsk Station)on the lower reaches of the Syr River fluctuate greatly from year to year,and the flow rate starts to increase in March every year,Reached the maximum from June to August,and thereafter the flow rate gradually decreased.The interannual changes of flow rates monitored by the three hydrological stations showed a downward trend overall,and the flow rate of Kazalinsk Hydrological Station decreased the most.Although the flow values monitored by the three hydrological stations increased in the late 1980 s,the magnitude was not large.(2)Calculate the design flood from the storm data,construct the rain-flood model function of Karaozek Hydrological Station in the watershed,and calculate the precipitation and corresponding frequency at the frequency of the 20-year,100-year and 1000-year occurrences of the relevant meteorological stations Flood peak flow value.The designed flood peaks are smaller than the actual situation,but in areas where hydrological and meteorological data are missing,or when it is difficult to collect high-precision basic hydrological data,using rain-flood statistics to design flood peak flows in this area is a valuable attempt.(3)The design flood is deduced from the measured flood flow data,and the design values of the flood peak flow at three frequencies of the Tomenaryq Hydrological Station in the 20-year,100-year,and 1000-year intervals are 4027.31m3/s,respectively.,4680.24m3/s,5598.61m3/s;the design values of the flood peak flow at three frequencies of Karaozek Hydrological Station are 2079.26m3/s,2498.74m3/s,and 3097.36m3/s;Kazalinsk Hydrological Station The design values of flood peak discharge at three frequencies in the reach are 2246.13m3/s,2891.19m3/s,and 3496.36m3/s.(4)According to the design value of flood peak flow,the HEC-RAS model is used to perform flood submergence simulation,and it is concluded that the elevation range of the water surface line in a 20-year encounter is 123.72 m ~ 116.21 m,and the maximum water depth from the water surface line to the river bottom is 5.93m;The elevation range of the water surface line is 124.28 m ~ 116.88 m,and the highest water depth from the surface line to the river bottom is 6.16m;the elevation range of the water surface line to the river surface during the millennium one is 124.76 m ~ 117.11 m,and the highest water depth from the surface line to the river bottom is 6.44 m.The maximum speed of simulated water flow is 7.6m / s.The HEC-RAS hydraulic model simulates the flooding process of the Syr Darya River and combines GIS visualization technology to plot the flooded submergence range.It can provide technical support for early warning of floods,evacuation planning,loss assessment,and the development of targeted flood control measures in the Lower Syr Darya River.