G.Akbari - Civil Engg, USB, Zahedan,Iran

A non-linear complete method of solution (NCM) for prediction of unsteady varied flow-sediment change at an estuary was developed and tested with river data. This method (NCM) then was compared with other available non-linear and linear implicit models when applied to some classical upstream flow-sediment variation problems showed better performances. An example of estuary was solved, to see how the models respond to a tidal variation downstream of a reach. The magnitude of nonlinear terms in the momentum and sediment continuity equations (1-5) increased due to rapid variation of flow. The model developed can simulate both steady and unsteady varied flows for water and sediment transport through rivers. Significance different between non-linear and linear models applied to flow –sediment routing case problems was treatment of the non-linear terms in the momentum and sediment continuity equations. The differences between the models were shown to be magnified when there was large spatial or temporal variation in discharge or depth in the case of high varied flow. Also coupled and uncoupled models differed in the treatment of boundary conditions and bed level changes ( ) term in the momentum equation In particular boundary conditions involving the term cannot in an uncoupled model.

Estuary , tidal flow , rapid varied flow , unsteady sediment flow , linear/non- linear coupled / uncoupled models [LCM , NCM , LUM , NUM]