Dynamics of flow structure, suspended sediment and morphology of large meandering rivers.

Lucas Gerardo Dominguez Ruben, Ricardo Szupiany, Jorge Abad, Hector Daniel Farias

Tuesday 30 june 2015

8:45 - 9:00h at Oceania (level 0)

Themes: (T) Sediment management and morphodynamics, (ST) River morphodynamics

Parallel session: 4B. Sediment - River

Meandering channels occurs in nature as one of the most common configuration and is the result of the complex interaction between fluid dynamics, sediment transport and bank material. Despite the numerous studies that analyze the dynamics of these rivers and, as a consequence of limited equipment an methodologies to quantified the mean variables, it is still required validations of the acting processes in large rivers of the world, which have as a distinctive feature high width/depth (w/d) ratios (typically between 20 to 100). In the present study, flow structure, suspended sediment transport and morphology are studied at two large meandering rivers with w/d ratios ranging from 19 to 58. Flow structure and suspended sediment transport, through specific methodologies, was measured with acoustic Doppler profiles (ADCP) over bends of each river during bankfull state. Results show distinctive characteristics from previous studies, such as: i) small and low intensities secondary circulation with poor effect on the redistribution of bed and suspended sediment along the bends, ii) different locations between cores of maximum velocity, concentration and secondary cells indicating particular processes governing the interaction between these variables, iii) low bed slope and absence of a second secondary circulation near outer bank, suggesting particular processes of bank retreat, iv) for high w/d ratios, a well and flat point-bar development with very gradual variation of cross bed slope.