April 13, 2022
Submarine Geohazards
In recent years, the development of cutting-edge measurement techniques has led to a substantial improvement in our knowledge of deep ocean currents. Of these, turbidity currents are the most intense, potentially destructive and difficult to predict. These deep flows of water and sand can reach speeds of the order of 5-20 m/s and run-out distances of the order of 100’s of kilometers. As such, they pose a risk to the design and maintenance of deep-water engineering structures such as oil and gas pipelines, telecommunication and power cable networks. Although we can measure these currents directly, our understanding of their formative mechanisms is still limited.
The numerical modelling techniques offered by WWS allow a full description of the triggering mechanisms through the coupling of atmospheric, oceanic and geological models. Our services provide not only detailed information on the triggering characteristics of these currents, but also on their probability by quantifying the events required to trigger them in the future. The results of our models help engineers at the design stage to mitigate risks by placing infrastructure in the most appropriate locations and introducing protective measures to reduce potential impacts. During operation and maintenance phases of a project, our models enable the design of the best solutions for the repair of damaged infrastructure.
Example from a study offshore the Phillipines where turbidity currents were responsible for displacement of a gas pipeline. Model flow velocity (vertically averaged) of turbidity current overlain on seafloor bathymetry offshore Mindoro Island shows the flow head at the point of impact on a subsea pipeline. The force of the flow displaced the pipeline by as much as 110 m at the canyon bend and 42 m farther down canyon compared to its installed position (see insets). Catastrophic flow events such as this are caused by specific conditions, including the intensity and track of the typhoon with respect to the coast and resulting interaction of waves, currents and river discharge. The numerical models contributed to the detailed design of mitigation measures to protect the pipeline and the optimization of operation and maintenance activities. Figure modified from Sequeiros et al. (2019) https://doi.org/10.1038/s41598-019-45615-z
We offer Services in the following areas:
Wind & wave hindcast analysis: Analysis of historical wind-wave climate at a site, probabilities of significant events, impact to sediment transport and catastrophic events (coastal erosion, submarine landslides, turbidity currents)
Turbidity Current Modelling 1.5D: Simplified numerical modelling coupled with morphologic analysis of submarine valleys. The simplified modelling approach allows for thousands of numerical simulations with variable input parameters enabling a statistical approach for geohazard assessment.
Integrated near-shore and offshore numerical models: Coupled coastal circulation models (wind, waves and currents) with turbidity current models to assess the triggering parameters for catastrophic events and their likelihood. A statistical assessment can be obtained through site-specific climate hindcast and forecast models, including rain-run-off modelling of the hinterland basin.
3D Turbidity Current Modelling: Full 3D modelling at the required spatial resolution and input parameter sensitivities enables determination of critical design parameters for offshore installations.
