摘要：Throughout the 20th century, many rivers worldwide have undergone
important riparian vegetation encroachment, which can be problematic in
terms of flood risks and biodiversity. Nowadays, controlled floods is often considered
as a management option in anthropized rivers, with the aim of limiting
vegetation encroachment within river channels, as well as maintaining a diverse
habitat by reactivating natural channel dynamics. In this context, this study aims
at investigating the influence of different flood regimes on river bar vegetation
development and dynamics, focussing on alternate bar systems which are typically
found in embanked streams. This question has been addressed through
two-dimensional bio-morphodynamic modeling of a simplified gravel bed river
reach. Four hydrological scenarios with different flood peak discharges have
been run for 50 years. For all scenarios, a steady increase in vegetation cover
strongly impacts the evolution of bar morphology, until a relatively stable equilibrium
is reached after one to three decades. Numerical results suggest that
vegetation development on bars is associated to an increase in bar wavelength
and a decrease in bar width. Higher peak flood discharges lead to narrower and
longer bars, and a longer adjustment duration. When vegetation cover is fully
developed, interannual flood variability seems crucial to maintain bedform and
vegetation turnover.
其他摘要：Throughout the 20th century, many rivers worldwide have undergone important riparian vegetation encroachment, which can be problematic in terms of flood risks and biodiversity. Nowadays, controlled floods is often considered as a management option in anthropized rivers, with the aim of limiting vegetation encroachment within river channels, as well as maintaining a diverse habitat by reactivating natural channel dynamics. In this context, this study aims at investigating the influence of different flood regimes on river bar vegetation development and dynamics, focussing on alternate bar systems which are typically found in embanked streams. This question has been addressed through two-dimensional bio-morphodynamic modeling of a simplified gravel bed river reach. Four hydrological scenarios with different flood peak discharges have been run for 50 years. For all scenarios, a steady increase in vegetation cover strongly impacts the evolution of bar morphology, until a relatively stable equilibrium is reached after one to three decades. Numerical results suggest that vegetation development on bars is associated to an increase in bar wavelength and a decrease in bar width. Higher peak flood discharges lead to narrower and longer bars, and a longer adjustment duration. When vegetation cover is fully developed, interannual flood variability seems crucial to maintain bedform and vegetation turnover.
