This week’s Environmental Dynamics Seminar is this Friday from 17:15-18:15 in the Pyramid Room (K4U.04). Dr Chris Hackney from the University of Hull will be talking about sediment transport on the Mekong River and the potential impacts of climate change on the sustainability of the Mekong delta. The results of the project have been recently published in Nature:
The world’s rivers deliver 19 billion tonnes of sediment to the coastal zone annually1, with a considerable fraction being sequestered in large deltas, home to over 500 million people. Most (more than 70 per cent) large deltas are under threat from a combination of rising sea levels, ground surface subsidence and anthropogenic sediment trapping2, 3, and a sustainable supply of fluvial sediment is therefore critical to prevent deltas being ‘drowned’ by rising relative sea levels2, 3, 4. Here we combine suspended sediment load data from the Mekong River with hydrological model simulations to isolate the role of tropical cyclones in transmitting suspended sediment to one of the world’s great deltas. We demonstrate that spatial variations in the Mekong’s suspended sediment load are correlated (r = 0.765, P < 0.1) with observed variations in tropical-cyclone climatology, and that a substantial portion (32 per cent) of the suspended sediment load reaching the delta is delivered by runoff generated by rainfall associated with tropical cyclones. Furthermore, we estimate that the suspended load to the delta has declined by 52.6 ± 10.2 megatonnes over recent years (1981–2005), of which 33.0 ± 7.1 megatonnes is due to a shift in tropical-cyclone climatology. Consequently, tropical cyclones have a key role in controlling the magnitude of, and variability in, transmission of suspended sediment to the coast. It is likely that anthropogenic sediment trapping in upstream reservoirs is a dominant factor in explaining past5, 6, 7, and anticipating future8, 9, declines in suspended sediment loads reaching the world’s major deltas. However, our study shows that changes in tropical-cyclone climatology affect trends in fluvial suspended sediment loads and thus are also key to fully assessing the risk posed to vulnerable coastal systems.
Chris will share highlights of their results and how science needs to move forward if the Mekong is to be healthy. As always, the seminar is free and open to the public. A drinks reception will follow.
