Model Of Bed Evolution, Health Assessment Of Wetland And Their Applications In Yellow River Estuary

Details are given in present paper of development of a sediment transport and morphological model to predict the bed evolution processes in tidal flows. There are four modules in the present coupled model which are hydrodynamic module, sediment transport module, bed evolution module and multi-layer bed module. The hydrodynamic module is based on shallow water equations and takes Coriolis force, wind induced stress and bed shear stress into consideration, wetting and drying processes are introduced to deal with moving boundary and Alternating Direction Implicit (ADI) technique is used to solve the hydrodynamic equations numerically. The sediment transport module has the capability of simulating the transport of graded sediments under non-equilibrium conditions. Cohesive sediment and non-cohesive sediment, suspended load and bed load are taken into consideration in present model. The fall velocity of suspended sediment is modified in present model due to the high sediment concentration. QUICKEST method is introduced to deal with the advective item. A 3-layer approach is adopted to simulate the variations of sediment gradations of bed materials.The model is tested against laboratory data obtained from a model harbour experiment, in which tide induced currents have caused gradual bed evolution around the harbour entrance. Details are given of the numerical model predicted water level,velocity distributions,bed level changes and their comparisons with the laboratory measurements. A comparison is also made between predictions made by the graded sediments model and those by a single size model.The model is used to simulate the bed evolution in the Yellow River Delta from 1992 to 1995. Field data are used to calibrate the parameters. The model is used to predict water and sediment transport in river channel and the mouth. The results show how the morphology developed in the Yellow River Estuary and agree well with the field data.A new index system is established in present paper to assess the health of Yellow River Delta wetland with the method of Fuzzy Comprehensive Assessment. The results show that the variation tendency during 1992 to 2008. Besides, economy assessments of Dongying were conducted each year in the same period, indicating that economic and health of wetland didn't develop coordinately. Five main influence factors were found by principal components analysis method, based on the five main influence factors, measures and suggestions of protecting the Yellow River Delta wetland are proposed for wetland managers.