The bulk of the sediment found on the abyssal plain is transported from
the shelf to the deep ocean by marine turbidity currents. They
consecutively erode, transfer and deposit large amounts of sediment
determining the characteristics of the marine environment. Further,
their destructive nature is evidenced by several failures of subsea
infrastructures that have been associated with their passage. Many
numerical models have been developed to study field-scale turbidity
currents. However, these models do not include sediment transport
processes typical of coastal settings. As such they currently require
the prescription of boundary conditions usually difficult to assess.
Here we present a new modeling approach to hindcast marine turbidity
currents that is based on a three-dimensional application of the
process-based model Delft3D capable of predicting the initiation of
sediment gravity flows driven by wind- and wave-induced processes.
Detailed numerical simulations were carried out to investigate the
nature of a turbidity current that impacted upon a submarine pipeline
offshore Philippines after the nearby landfall of a tropical cyclone.
Our simulations predict the triggering of a severe turbidity current
only after the passage of the aforementioned tropical cyclone and the
absence of any significant undercurrent associated with the other most
relevant cyclones that passed near the study area during the lifespan of
the pipeline, matching field observations in the form of pipeline
shifting. Numerical results describe the development of rip currents
that flush out water and sediment in cross-shore direction, ultimately
triggering a turbidity current into the submarine canyon that cross the
pipeline where its displacement was detected. Collapse of similarity
profiles of the predicted undercurrent with experimental measurements
and field observations demonstrates the reliability of the model in
capturing the vertical structure of turbidity currents. As Delft3D has
been demonstrated to accurately reproduce sediment transport processes
associated with different environmental pressures in various
geomorphological settings, the proposed modelling approach will allow
for a deeper understanding of the mechanisms involved in the initiation
of marine turbidity currents and their potential forecast.