Numerical experiments to explore bar management by channel width variations.

Gonzalo DurĂ³, Alessandra Crosato, Pablo Tassi

Tuesday 30 june 2015

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

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

Parallel session: 7B. Sediment - River

Managing river bars can reduce costs and optimize river engineering works to free water intakes, enhance navigation and improve ecosystems. This work explores ways to locally suppress alternate bars by either narrowing a finite river reach or imposing symmetry of flow and bed topography at a given cross-section. This work explores also the possibility of restoring alternate and central bars by channel widening, a practice that is often implemented in river rehabilitation projects. The investigation is based on the application of a two-dimensional depth-averaged hydro-morphodynamic model, previously validated on field data and experimental observations. Numerical results suggest that it is possible to achieve a bar-free reach by narrowing the channel for a distance equal to ten times the original width. Moreover, channel widening from either a stable bar-free or an alternate-bar dominated channel leads to a compound bar mode of coexisting alternate and central bars. Although the numerical results show coherence when comparing with a physics-based bar mode estimation formula and qualitative field observations, these findings still need further experimental and field confirmation.