Time scales for scour below pipelines and around vertical piles due to nonlinear random waves

This paper provides a practical stochastic method by which the time scale for the equilibrium scour depth below pipelines and around slender vertical piles exposed to long-crested (2D) and short-crested (3D) nonlinear random waves can be derived. The approach is based on assuming the waves to be a stationary narrow-band random process, adopting the Forristall (2000) wave crest height distribution representing both 2D and 3D nonlinear random waves. Moreover, the time scale for regular waves given by Sumer and Fredsøe (2002) are used. Examples of results are also presented.