Environmental Engineering - Scotian Shelf - Wind and wave hindcasting

Martec carried out a study for Mobil Oil Canada to predict extreme wave conditions on the Scotian Shelf, for the development of design wave criteria for the Sable Offshore Energy Project. This study involved wind and wave hindcasting for hurricanes and extratropical storms, as well as wave refraction and extremal analysis for selected sites.

Hindcasting of wind fields and wave conditions was performed by applying the Canadian Spectral Ocean Wave Model (CSOWM) to hurricanes that might have severely affected the Scotian Shelf over the time period from 1896 to 1996. CSOWM is a state-of-the-art 3G-WAM shallow water wave model operated twice daily by Environment Canada. Hindcast wind fields and directional wave spectra were also obtained from a study of 78 severe extratropical storms occurring from 1957 to 1995.

The wind fields and 2-D wave spectra for the extratropical storms and hurricanes were used as input to local wave refraction analysis using a steady state spectral model for near-coast wave simulations. The wave refraction model is a natural extension of the 3G-WAM model, which was used to simulate the transformation of a directional wave spectrum as it propagates into shallower waters on the Scotian Shelf. The wave refraction analysis provided wave heights, periods and directions at the proposed platform sites and selected sites along the pipeline route (shown in yellow).

The local wave conditions generated by the hurricanes and extratropical storms were used to derive estimates of extreme wave conditions at each site. The extremal analysis was carried out using standard techniques that fit cumulative probability distributions to the wave data. The distribution giving the best fit to the data at each site was used to derive design criteria for significant wave height and maximum expected wave height for return periods of 1, 10, 20, 50 and 100 years.