Elsevier

Geomorphology

Volume 305, 15 March 2018, Pages 209-220
Geomorphology

A model of water and sediment balance as determinants of relative sea level rise in contemporary and future deltas

https://doi.org/10.1016/j.geomorph.2017.09.040Get rights and content
Under a Creative Commons license
open access

Highlights

  • A delta sediment balance model is developed for a global selection of deltas.

  • Sediment flux and relative sea-level rise vary under modern and future scenarios.

  • Watershed and coastal sediment processes outweigh sea-level rise in some deltas.

  • Full use of hydro-resources in upstream basins strongly impacts downstream deltas.

Abstract

Modern deltas are dependent on human-mediated freshwater and sediment fluxes. Changes to these fluxes impact delta biogeophysical functioning and affect the long-term sustainability of these landscapes for human and for natural systems. Here we present contemporary estimates of long-term mean sediment balance and relative sea level rise across 46 global deltas. We model scenarios of contemporary and future water resource management schemes and hydropower infrastructure in upstream river basins to explore how changing sediment fluxes impact relative sea level rise in delta systems. Model results show that contemporary sediment fluxes, anthropogenic drivers of land subsidence, and sea level rise result in delta relative sea level rise rates that average 6.8 mm/y. Assessment of impacts of planned and under-construction dams on relative sea level rise rates suggests increases on the order of 1 mm/y in deltas with new upstream construction. Sediment fluxes are estimated to decrease by up to 60% in the Danube and 21% in the Ganges-Brahmaputra-Meghna if all currently planned dams are constructed. Reduced sediment retention on deltas caused by increased river channelization and management has a larger impact, increasing relative sea level rise on average by nearly 2 mm/y. Long-term delta sustainability requires a more complete understanding of how geophysical and anthropogenic change impact delta geomorphology. Local and regional strategies for sustainable delta management that focus on local and regional drivers of change, especially groundwater and hydrocarbon extraction and upstream dam construction, can be highly impactful even in the context of global climate-induced sea level rise.

Keywords

River deltas
Sea level rise
Environmental change
Coastal geomorphology

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