Deltas are highly dynamic: they evolve through the interaction of sediment delivery, redistribution and export. They need sediment to survive, especially with increasing rates of relative sea-level rise. At the same time, sediment delivery to many deltas worldwide is decreasing significantly.
A majority of the world’s major deltas will experience reduced sediment delivery
Frances Dunn, postdoctoral researcher on fluvial sediment delivery to deltas using computational modelling, found, “A majority of the world’s major deltas will experience reduced sediment delivery by the end of the 21st century (Storyline: The future of our deltas)". These declines are driven by human interventions in the catchment, such as changing land-management practices and river damming.
Delta loss or gain?
Jaap Nienhuis, assistant professor of coastal morphodynamics, found that over the past 30 years deltas globally experienced net land-area gain. "But", says Jaap Nienhuis, “these land gains are unlikely to be sustained in the coming century as sea-level rise, tides and waves become more important in shaping delta coastlines”. Under the RCP8.5 climate scenario, with an average sea-level rise of 0.62 m by 2100, 31% of all currently river-dominated deltas will transition to having tides or waves as the main force behind coastal erosion.
Researchers at the Water, Climate and Future Deltas hub investigate what happens with sediment in the delta when sediment delivery changes and seek sustainable strategies for sediment management. Tracing sediment flows through different parts of the delta is the first important step towards understanding.