Research Of 2D Water And Sediment Numerical Modeling Based On GIS And Its Application In The Lower Yellow River

A 2D water and sediment numerical model in the lower Yellow River was developed aimed at flow and sediment transport characteristics and based on GIS platform.By comparing the development of numerical modeling technologies in the world, equation discrete schemes and methodologies suited for hyper-concentration flow are selected .The Osher and LSS schemes are used to calculate the convection term of water and sediment. The Gauss theory is adopted to induce the control volume central gradient of the diffusion term. Solutions of the equations with forecasting and adjusting two-steps method may ensure results have real physical means and fit well with characteristic construction of solution, which has flux conservation, upwind, monotonic keeping and high resolving power for discontinuity . As for the unbalance momentum induced from water pressure non-uniform with river bed slope, the Gauss theory is used to calculate averaged flux of each side, which not only avoids the error flow phenomena for steep water depth gradient, but also shows the distribution of status vectors correctly. The paper studies the key problems including non-uniform sediment settling velocity, suspend sediment transport capacity, bed sediment composition adjustment, movable bed roughness variety, turbulence viscous coefficient, sediment viscous coefficient and transverse bank scour simulating. By using ArcGIS and secondary developing with GIS, the model's pre-processes and post processes include grid generation system, digital elevation generation system and flow field visualization system.A typical testing procedure is used to test the flow module and sediment module, including processes of steady and unsteady flow, dam break flow, impressed flow, compounded river channel and complex boundary conditions. Data of conventional measurement in the Lower Yellow River and special observations for this study are used to calibrate the sediment settling velocity, movable bed roughness coefficient and gradations sediment transport capacity etc. Sets of scenario studies are carried out. Several typical flood processes are verified and results prove that the model can be satisfied for the flood management in the Lower Yellow River.The innovation achievements of the paper may be summarized as follows: Based on numerical method and sediment transport law with developed IT technology, realized the combination of IT technology with water science; Numerical methodologies of hyper-concentration flow and research on key problems of hyper-concentration flow fundamental theory improve the modeling precision for hyper-concentration flow. Based on GIS platform, not only improve the efficiency but also improve the precision of digital elevation generation, information searching speed and visualization technology obviously.