A Composite Mathematical Model for the Wandering Reach in the Lower Yellow River

The fluvial process is considerably complicated in the wandering reach of the Lower Yellow River, and the lateral or transverse bed deformation process is pronounced especially. This paper analyzes the state - of - the - art of simulation techniques for the bed deformation in the Lower Yellow River, and such a conclusion is drawn that existing sediment mathematical models only can simulate the longitudinal bed deformation, and cannot simulate such the lateral deformation as bank erosion and failure. Then a new 2D composite model is established in this paper, consisting of a 2D flow - sediment mathematical sub - model and a riverbank - erosion sub - model. It not only can simulate the longitudinal and lateral deformation of riverbed, but also can be used to simulate the fluvial processes of natural rivers, especially the Lower Yellow River. Through using the proposed composite model, the flood routing and bed deformation processes during the August 1982 flood are simulated. The maximum stage along the reach and the discharge hydrograph at the outlet so obtained are in good agreement with the observed data. Simulated results of the bed deformation processes show that during the flood season, the main channel scours and the flood plain deposits; during the dry season, the main channel deposits and banks of the floodplain retreat due to lateral erosion by flow and failure under gravity. Such results accord with the annual law of scouring and deposition variation in the wandering reach.