On the modeling of the initial formation of offshore tidally generated sand waves

Abstract

Sand waves are rhythmic morphological features on the sea bed that are observed in sandy shallow seas. These bed formations occur in large parts of the North Sea and have a typical wavelength of hundred meters and heights of up to 10 meters. Sand waves are dynamic, meaning that they can migrate up to 10 meters per year. Because of their widespread occurrence and the dynamic behavior they may endanger human activities. For example, a migrating sand wave may expose cables from a wind farm or even narrow down ship routes. So, understanding of sand wave behavior is key to safe offshore activities. Characteristics of sand waves, like migration speed and growth, are difficult to monitor for large parts of the sea and are often investigated through (non-)linear stability models. In this study, the sensitivity of sand wave characteristics to environmental parameters, such as water depth, grain size, and tidal current strength, are investigated by applying a linear stability analyses in a process-based model. This model uses a new formulation for the turbulence closure relation and uses site specific environmental parameter input. The model results are compared both with a state of the art numerical model, namely Delft3D, and observations.