The effect of unsteady hydrographs and non-uniform sediment transport on morphology of pool-riffle sequences.

Esmaeel Bayat, Jose Rodriguez, Gustavo Adolfo Mazza de Almeida, Patricia Saco, Elham Vahidi

Monday 29 june 2015

16:45 - 17:00h at Oceania (level 0)

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

Parallel session: 3B. Sediment - River

The effect of unsteady hydrographs on morphodynamics, especially during flood hydrograph events, is one of the most important factors for deformation in channel morphology. The stability of pool-riffle sequences depends on multiple mechanisms. The combination of sorting and flow unsteadiness help explain how features like pool-riffle sequences can be stable for a long time. In this paper, effect of unsteady hydrographs flows and non-uniform sediment transport on long term stability of pool-riffle sequences is considered. The results will be based on field data and also on a 1-D hydromorphological model that considers fractional sediment transport and sorting. By using this model the effects of asymmetry, peak flow and duration of a hydrograph will be considered. This simulation can compare the sediment transport process during rising and falling limb. The different temporal lag between peak flow conditions and peak bed-load transport, as an important factor for self-maintenance in pool-riffle sequences will be discussed.