Characteristics and mechanism of wandering intensity adjustments in a wandering reach of the Lower Yellow River after the operation of the Xiaolangdi Reservoir
To quantitatively explore the adjustments in the wandering intensity in a wandering reach of the Lower Yellow River(LYR)since the operation of the Xiaolangdi(XLD)Reservoir,the calculation method of a new wandering index(WI)was proposed.In addition,Landsat images were collected to perform an analysis of the spatio-temporal variations in the wandering intensity and their response to major influencing factors.The results indicate that the wandering intensity in the wandering reach integrally presented a decreasing trend during the period from 2000 to 2022,with the value of WI decreasing from 0.918 to 0.674 and changing rate being fast to slow.Specifically,the wandering intensity in the Tiexie-Yiluohekou reach and Huayuankou-Jiahetan reach has decreased,while the Yiluohekou-Huayuankou reach maintained and the Jiahetan-Gaocun reach increased.Furthermore,the wandering intensity adjustments had close relations to the flow-sediment regime,riverbed boundary conditions and local river regime evolution.For flow and sediment regime,the decrease of wandering intensity in the wandering reach was significantly attributed to the sharp reduction in the incoming sediment volume and rising-recession rate of floods in the LYR owing to the operation of XLD Reservoir,which resulted in the riverbed erosion and flow concentration in the downstream channel.Regarding riverbed boundary conditions,the wandering intensity in the sub-reaches with strong lateral restrict caused by banks or channel regulation works tended to decrease.Also,the increase in the longitudinal stability of the riverbed was one of the reasons why the wandering intensity in the wandering reach declined with a slower changing rate in the later stage.Concerning about propagation of river regime adjustments,the frequent occurrence of avulsion in the Jiahetan-Gaocun reach during the later period was mainly attributed to the river regime evolution in the inlet reach between Zhuzhai to Dongbatou.
wandering intensityspatio-temporal variationsevolution mechanismwandering indexLandsat imageLower Yellow River
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