Study On Compoud Hydrodynamic Conditions In Terminnal Of Fluctuating Backwater Reach Of Of Three Gorge Reservoir And Its Influence Of Sediment Transport

Chongqing urban river is very complex because of its continuous curved planarconfiguration, special streambed structure that spread many moraines under the riverand rocks, the middle reaches of JiaLing river inflow and so on. With the operation ofthe Three Gorges Reservoir area reach175m scheme，urban river in a storage period anddraw-off period will influenced by fluctuating water, the flow condition and gravelmovement become more complexity. This article is based on prototype observation dataof hydrological and river bed elevation to discuss about the following by the SMS2Dmathematical model under the complex hydrodynamic condition.1. Through the comparison of change process of XuanTanmiao hydrologic stationbefore and after impoundment，getting the critical time、mainstream discharge、waterlevel value that the conversion between natural river and reservoir reach on Chongqingurban river reach.2. By means of mathematical model，calculating the critical upstream water levelthat terminal of backwater effect on CunTan hydrologic station on each flow grade, andanalyzing its change law with the discharge of CunTan hydrologic station.3. Set up the mathematical model of Chongqing urban river reach, simulate itsflow characteristics under each represents flow before and after impoundment based onmeasured data, and analyze the effect of hydrodynamic conditions due to reservoirfluctuating.4. After impoundment, the stream power of Chongqing urban river reach have adrastic change, According to the calculation of critical size, it think that the influence offine particle greater than coarse particle under the change of hydrodynamic conditions.The result of prototype observation is the same as the analysis by analyzing riverbed elevation data of measured section that consist of sediment and gravel. Meanwhile,it summarized the reason of impact and siltation before and after impoundment.5. According to the achievement of ZhuErqi reach physical model, analyzing themain transportation of gravel shoal on Chongqing urban river reach.6. There are several reasons that make different between measured data andphysical model. First the reduce of incoming sediment、river bed armoring. Second, thesedimentation of downstream not significantly, tailrace not elevation, operating life is shorter. Last, the cumulative change process is not yet clear.With the operation of the Three Gorges Reservoir area reach175m scheme, theinfluence on gravel of reservoir fluctuating are as follow. First, sediment transport stagefrom terminal flood season to early draw-off period. Second, sediment transport dayfrom250falls to53. Last, sediment area close up to dredged channel, the width reduce.