| The Song Hua River waterway is the inland waterway through Jilin Province,and is also an important waterway to communicate with the main stream of Song Hua River and Neng River.In order to further accelerate the development of inland river shipping in Jilin,it is proposed to improve the waterway of Jilin section of Songhua River and achieve the goal of resuming navigation of the entire Class IV waterway.This paper briefly analyzes the current situation of the channel and the evolution of the riverbed in the Jilin section of the Songhua River by collecting hydrological,topographic and sediment information,and constructs and verifies a planar twodimensional water flow mathematical model of the Jilin section of the Songhua River based on MIKE21,and analyzes the channel conditions and the obstructive characteristics and causes of the key beach sections under different working conditions.Three remediation options were proposed,and the recommended options were analyzed in terms of channel scale,river core specific drop,main channel flow velocity,hydraulic index of beach elimination,flow pattern of key beach sections,impact of the remediation project on urban water diversion and irrigation district water intake,and impact of the remediation project on the river landscape.This paper provides technical support for the channel improvement project of Jilin City section of Songhua River.The main research results of this paper are:(1)Combined with the topographic data in 2017 and 2021,the riverbed evolution analysis is carried out from several aspects,including overall erosion and siltation changes,typical cross-sectional changes,longitudinal changes in the deep flood line,planar changes in the deep flood line,and changes in the beach channel,and the characteristics and trends of the riverbed evolution in the studied river section are obtained: the upstream Fengman Dam and Yongqing Junction intercept sand causing the discharge of clear water,and the Jilin City section of the Songhua River mainly appears to be undercut in the longitudinal direction,with the whistling There is a certain amount of siltation in the reservoir area of the river barrage,but the siltation magnitude is not large;the river potential is basically stable on the plane,and no major evolution has occurred.In the future,the river potential will be more stable,and there will be some down-cutting trend in the longitudinal direction.(2)Based on MIKE21,we constructed and verified the planar two-dimensional water flow mathematical model of the Jilin section of the Songhua River,and analyzed the channel conditions and the obstruction characteristics and causes of the key beach section under different working conditions.The length of the river section that does not meet 1.6m in the dry period of the Songhua River Jilin is about 4.8km,the 1.6m isobath does not penetrate the channel,and the steep ratio drop of the local river section reaches4.38‰;the navigation depth increases in the middle flood period,and the water depth at the Anda village,the down cow post beach and the channel pier is less than 1.6m,which does not meet the construction standard of the Class IV channel.Under each flow rate,the water surface line of the Jilin section of the Songhua River shows a "stepped" shape with steep slope and rapid flow,accompanied by bad flow patterns.The navigational characteristics of the key beaches were analyzed: the river section of the railroad bridge at Jiu Station is a typical fast-flowing beach,with dense bridge piers and construction buildings occupying most of the river crossing area,resulting in a significant contraction of the water flow;the shallow water and narrow channel of the Niuhuizhang beach,with a fast flow at the mouth and cross-flow and other obstructive currents,with shallow beaches occupying the river channel and the flow tending to the left,resulting in significant cross-flow;the shallow water,narrow bends and fast local currents and bad flow patterns of the Anda Village,due to The main reason is that the right side of the beach development is seriously crowding the river channel,and there are deep pits locally;the channel dock is mainly shallow obstruction of navigation,affected by the relaxation of the river potential,slowing down the flow of water,sediment is easy to siltation,resulting in scattered shallow package exposed;the section of Jiu station irrigation area is mainly shallow obstruction of navigation,accompanied by cross-flow obstruction of navigation,the river pebble pile and water stopping Ding dam have obvious provocation effect on the flow of water.(3)Analysis of the navigational constraints of the Jilin City section of the Songhua River,and proposed three remediation options,from the scale of the channel,the river core specific drop,the main channel flow rate,the elimination of the beach hydraulic indicators,the key beach section flow patterns,channel remediation on urban water diversion and irrigation district water intake,the impact of the remediation project on the river landscape for a comprehensive selection analysis,the results show that: a single channel dredging(option 1),can not effectively improve the project There is also a steep drop and water fall,with a drop of 3.34‰ at the railroad bridge section in the dry season and a drop of 0.73 m in the water surface of the bridge area,which is an improvement compared with the previous plan,and the dredging and excavation of the bridge area and the remediation area lead to a significant drop in the upstream water surface line,and there are shallow beaches on both sides of the local river channel,which will damage the urban river landscape;compound section remediation(plan 2)can weaken the steep drop of the key obstruction The steep ratio drop of the navigable beach section,the ratio drop of the river section at the railroad bridge of Jiuzhang and the channel pier are reduced,but the ratio drop at the river section at the railroad bridge of Jiuzhang is still large,and the water depth of the river section from the irrigation area of Jiuzhang to the railroad bridge of Jiuzhang is less than 1.6 m.The compound section excavation can readjust and redistribute the water depth of the side beaches,and the exposed area of the shallow beaches is obviously reduced,but the dredging and clearing lead to the obvious water level drop of the upstream river section,which adversely affects the normal operation of the water intake and diversion projects in the river.However,the dredging and clearing led to a significant drop in water level in the upstream section,which adversely affected the normal operation of the water extraction and diversion projects in the river;after the combination of compound section remediation and channelization project(Option 3),the scale of each channel reached the standard of Class IV channel,the bad flow pattern was eliminated,the overall smooth flow in the river,which had less impact on the water intake and irrigation area,and the exposed area of the shallows was significantly reduced,which also had less impact on the urban river landscape.Overall,Option 3 is the recommended option,taking into account the navigable water flow conditions,urban water intake and irrigation area water diversion and river landscape. |
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