Sediment Transport

The erosion, transport, and deposition of sediment is one of the fundamental processes responsible for shaping our planet and generating the geological record. It is also a subject of significant environmental interest because human populations often seek to mitigate the impacts of sediment erosion and deposition in rivers, lakes, estuaries and coastal settings, and sediments are subject to contamination by pollutants.

Cabled observatory technology can contribute to our understanding of sediment transport by hosting experiments that will characterize the role of sediment transport in shaping the continental margin, creating the stratigraphic record, and transporting sediments, carbon, and anthropogenic chemicals to the deep sea. The rugged terrain of the Pacific Northwest, the high coastal rainfall, and the narrow continental shelf all result in large fluxes of sediment across the northeast Pacific continental shelf to the adjacent deep-sea floor. Yet the characteristics of this sediment flux are poorly known in part because most of the flux occurs episodically during major storms.

Experiment Design

The near-coastal portion of the Regional OOI and related buoyed infrastructure will facilitate long-term deployments of instruments arrays that will record the frequency, intensity, and characteristics of sediment transport arrays events. Instruments deployed near the seafloor will provide continuous baseline data on near-bottom currents and suspended sediment concentrations and can be triggered either by local events or a remote operator intervention to collect more extensive data and samples. The availability of ample power and bandwidth will allow both measurements and sampling under severe storms at spatial and temporal scales that are not feasible using surface vessels under such conditions.

The experiments connected to the cabled infrastructure will focus on fine particles and will build on past work off the Eel and Columbia Rivers. Initial emphasis will be on the sediment-water interface at the shelf break. In addition to observations and sampling, the technology will allow fluid and particle tracer experiments. The availability of mobile autonomous underwater vehicles and seafloor rovers will extend fixed arrays and will allow transects to be re-occupied and re-sampled over time.