Abstract
Many of the world’s major river deltas face a sustainability crisis, as they come under threat of increases in salinity and the extent of tidal zones forced by combinations of sea-level rise, changes in river discharge and channel geometry. The relative contribution of these factors to future increases in tidal extent remains unconstrained, with most prior work emphasising the role of climate-driven sea-level rise. Here we use new field data from the Mekong delta to measure variations of river discharge and changes of channel geometry, and project them into the future. We combine these with projections of future sea-level rise into a 2D hydrodynamic numerical model and quantify the influence of the different driving factors on future tidal extension into the delta. We show that within the next two decades, tidal extension into the Mekong delta will increase by up to 56 km due to channel deepening (92%), dominantly driven by anthropogenic sediment starvation. Furthermore, even under strong mitigation scenarios, sediment starvation still drives a long-term commitment to future tidal extension. Specifically, by 2098 eustatically rising sea-levels are predicted to contribute only modestly to the projected extension. These findings demonstrate the urgent need for policy makers to adopt evidence-based measures to reverse negative sediment budgets that drive tidal extension into sediment starved deltas.
Highlights
The world’s deltas occupy less than 1% of the global land surface, but 4.5% of the global population lives on them (Edmonds et al 2020)
We focus on the Mekong delta because it is classified by the Intergovernmental Panel on Climate Change (IPCC) as one of the three most vulnerable deltas globally (Parry et al 2007) and because it is representative of other large deltas in terms of the multiple drivers of change it is experiencing, and in its response to these pressures
Should channel bed lowering continue unmitigated, the tidal extent (TE) in the Mekong delta will rapidly increase by ∼56 km in the two decades
Summary
Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. G Vasilopoulos1,∗ , Q L Quan1,2, D R Parsons1, S E Darby3, V P D Tri4, N N Hung2, I D Haigh5 , H E Voepel3, A P Nicholas6 and R Aalto6 Keywords: river deltas, tidal extension, sediment starvation, climate resilience Any further distribution Supplementary material for this article is available online of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
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