Vertical Erosion And Deposition Of Alluvial River And Lateral Deformation Numerical Simulation Studies And Applications

This thesis reviewed at fist the existing results of the physical mechanisms and simulationtechniques of lateral river channel changes. In order that the numerical model developed be basedon sound foundations, Several fundamental aspects relating to cohesive river bank erosion andcollapse in alluvial rivers, such as the lateral f1uvial erosion at the base of the banks, the stabilityanalysis of riverbanks, the physical properties of failed bank materials, and the interactions betweenlateral and longitudinal channel deformation, were investigated .The quasi-2D model developed inthis thesis can simulate both the lateral and longitudinal channel deformations, and is applicable toheavy sediment carrying alluvial rivers with sand bed and cohesive riverbank materials. The lateraland longitudinal distribution of hydraulic variables are obtained, at the first step, by coupling the1D gradually varied flow equations and the simplified 2D flow equations. Secondly, thelongitudinal channel deformation is obtained by solving the sediment continuity and river beddeformation equations for every grain size group. The lateral channe1 deformation is determinedfinally by the analysis of river bank stability of both sides. The materials of the bank erosion in atime step is divided into two groups, bed material and suspended load. The former deposits on theriverbed in that time step, and the later is transferred to the sediment transport equations in the nexttime step, there-by the interaction between the lateral and the longitudinal channel deformation isaccounted for. Besides, several important issues relevant to the modeling of the lateral andlongitudinal channel deformation in alluvial rivers are discussed. The salient point are as-follows:(1)The coefficient of saturation recovery(CSR) for non-equilibrium transportation of non-uniformsuspended load is investigated, and the primary conclusion is that the CSR of a size group is ininverse proportion to its particle size; (2) It is discussed in detail the physical processes andmechanisms of both the fluvial and the gravitational bank erosion as well as the numerical methodof them; (3)The discussions of the water surface elevation impacts on the bank stability, thelongitudinal extent of the bank failure, and the physical properties of the failed bank materials arealso worthy of note.The proposed numerical model has been used in the simulation of the river channeldeformations during l960 to l990 in the San-men-xia reservoir. The computed results of the modelare consistent well with the measured ones. Finally, the model is used for predicting the riverchannel changes in Xiao-lang-di reservoir at four different application manners.