Two-dimensional (2D) depth-averaged numerical modeling of a braided river morphodynamics upstream of a dam reservoir.

Abstract: The river morphology of a braided type river is rather complex. High sediment transport rates and frequently changing discharges are the cause of dynamic planform evolution. The coexistence of alternating bars and the consequent appearing confluences and divergences in interaction with bank erosion have been in the focus of scientific investigations over the last decades. It is still rather challenging to estimate or predict the total sediment transport rate in such type of rivers. The present study attempts to numerically simulate such complex morphodynamics in a braided river reach. A reach of the Devoll River in Albania, located upstream of the Banja dam, is considered. The morphodynamics of this river reach is important as there is an expanding delta upstream of the dam reservoir. The objectives of the two-dimensional (2D) depth-averaged approach of the present study are (i) to show the ability of the HEC-RAS 2D model to simulate the evolution of this braided river, (ii) to evaluate the variation of Braided Index (BI) of chosen reach along the time of input hydrograph, and (iii) to illustrate an applied context to consider future modeling challenges. HEC-RAS 2D uses the shallow water equations solved with an implicit finite volume solver, and the Wu transport formula to solve the sediment transport rate and the corresponding bed changes. The preliminary results are promising to reveal the expected evolution trend of the mentioned braided river.     «

Abstract: The river morphology of a braided type river is rather complex. High sediment transport rates and frequently changing discharges are the cause of dynamic planform evolution. The coexistence of alternating bars and the consequent appearing confluences and divergences in interaction with bank erosion have been in the focus of scientific investigations over the last decades. It is still rather challenging to estimate or predict the total sediment transport rate in such type of rivers. Th...     »