Hydrodynamic Modelling and Design Water Level

Hydrodynamic Modelling and Design Water Level

Storm surge, set-down and design water level are key parameters for the design of coastal structures, whether a flood defence a seabed scour protection or the deck of a jetty.

For structures on the sea-bed, it is not always the combination of the highest water level and extreme waves that give the determining design conditions; sometimes a lower water level results in more severe conditions. BMT Ship & Coastal Dynamics (BMT) understands how to deal with this from both a modelling perspective and statistically. We also understand how to analyse storm-surge and combine this with astronomical tide to get appropriate design conditions (skew surge). We have considerable experience with a range of methods to get the storm surge:

  • Analysis of long term water level measurements;
  • Using 1D hydrostatic models (conservative estimate suitable for feasibility phase);
  • Simulating historical storms using hydrodynamic models such as TUFLOW FV and ADCIRC;

TUFLOW FV is an advanced coastal 3D hydrodynamics model developed by BMT WBM which has an extensive track record including projects where it has successfully been nested in ocean models.

BMT works with BMT WBM for most projects where advanced flow modelling is needed. TUFLOW FV employs a Finite Volume numerical scheme to solve the relevant 3D primitive hydrodynamic equations on a flexible mesh comprised of triangular and quadrilateral elements (in a horizontal plane).

One advantage of employing a flexible mesh model is the ability to adjust the spatial resolution of the computational network, and in particular to increase resolution in areas of specific interest to the study while avoiding excessive computational expense due to unnecessarily detailed representation where this is not required. 

In particular in coastal regions a flexible mesh allows for much more detailed and accurate representation of complex shorelines and bathymetries and the influence that these have on flow fields (see example in the figure above).

There is also a coastal morphology module, TUFLOW-ST, for simulating the transport and fate of cohesive (muds) and non-cohesive (sands) sediment

BMT also has experience in applying the ADCIRC model, which can be coupled with the SWAN model at machine code level to represent wave current interactions.