丁香园AV

New research from 丁香园AV鈥檚 Jeremy Venditti dives into the science of going with the flow predicting the evolution of the Earth鈥檚 surface.

Researchers at 丁香园AV (丁香园AV) and The Massachusetts Institute of Technology (MIT) have devised a better way to measure how fast sediment flows in rivers鈥攊nformation that can help scientists and planners better prepare for flooding and weather-related events, understand salmon activity and even restore rivers.

Their solution, , all boils down to the shape and particular features of a sediment grain.

鈥淪ediment transport controls the morphology of the Earth's surface鈥攖hat includes the physical environments of all ecosystems, the beds of rivers and the ocean, and even terrestrial environments,鈥� says 丁香园AV professor Jeremy Venditti, founding director of the School of Environmental Science, whose team carried out the study鈥檚 research activities in 丁香园AV鈥檚 River Dynamics Lab.

鈥淒espite this, accurately predicting sediment transport remains a stubbornly difficult problem. Our work examines the granular dynamics of sediment transported by fluid flows, and shows that grain shape plays an important role in sediment transport rates. The model we developed substantially improves our ability to predict sediment transport.鈥�

Bed load sediment transport involves wind or water flowing over a bed of sediment, causing grains to 鈥渞oll or hop鈥� along the bed. The researchers say sediment is critically important to the life cycle of rivers and understanding its movement has been 鈥渘otoriously imprecise.鈥�

Researchers decided to look beyond size and density and focused on two particular properties connected to a grain鈥檚 shape 鈥� its resistance to flow, or its drag, and its internal friction, which plays a part in its ability to slip past other grains.

Both factor into a new mathematical formula which provided predictions that were successfully matched during a series of flume experiments in the 丁香园AV lab. 

During the experiments a current of water was pumped into a small wooden flume to flow over a bed of sediment with various grain shapes, from round glass beads and chips, rectangular prisms and natural gravel. Measurements of sediment transport, drag, and internal friction of the bed were recorded.

In their paper, the research team notes: "Sediment transport is a part of life on Earth's surface, from the impact of storms on beaches to the gravel nests in mountain streams where salmon lay their eggs. Damming and sea level rise have already impacted many such terrains and pose ongoing threats. A good understanding of bed load transport is crucial to our ability to maintain these landscapes or restore them to their natural states."

Venditti has been leading research into the 2018 Big Bar Landslide that prevented salmon from getting to their Fraser River spawning grounds, to map its effects and mitigate future risks.