Multidecadal Evolution of the Turbidity Maximum Zone in a Macrotidal River Under Climate and Anthropogenic Pressures

Climate and human pressures can influence the evolution of estuarine sediment dynamics concurrently, but understanding quantification their cause–effect relationships are still challenging due to occurrence complex hydro-morpho-sedimentary feedbacks. The Garonne Tidal River (GTR, upper Gironde Estuary, France) is a clear example system stressed by both anthropogenic climate change, as it has been subject decreasing river discharges, natural morphological changes, gravel extraction. To understand relative effect each hydrological geomorphological pressure on turbidity maximum zone (TMZ), in GTR over last six decades was evaluated using width-averaged idealized iFlow model. Model results show gradual increase tidal amplitude currents that led upstream shift landward sediment-transport capacity components (external M4 tide, spatial settling lag, return flow). displacement TMZ between 1950s 2010s estimated be at least 19 km, which about three fourth induced changes one changes. Concerning lower morphology main inducing GTR. Anthropogenic bed roughness itself also contributed this evolution. were, turn, probably promoted dynamics, so study reveals closed circle governs intensification TMZ.