Environmental Engineering - Sable Offshore Energy Project - Hydrodynamic modeling

A monitoring program was carried out to assess the environmental effect of pipeline trenching operations on areas near the landfall site in Stormont Bay. Hydrodynamic modeling of the nearshore region was conducted to examine circulation patterns in order to predict whether currents would transport suspended sediments toward sensitive biological areas.

A finite element model was set up using the coastlines and bathymetry of Country Harbour, Isaacs Harbour and Stormont Bay, extending offshore to 45? N latitude. Since field data indicate that the region is not dominated by wind-driven currents or density flows, the boundary conditions are based on tidal elevations measured at the Port Bickerton tide gauge station. The depth-integrated model solves the nonlinear shallow water equations to generate water surface elevations and tidal current velocities.

Field measurements of flow discharge through Stormont Bay indicate a consistent high frequency oscillation 8 times the dominant semidiurnal (M2) flow. Based on estimates of the natural period of Stormont Bay and Country Harbour, it is possible for the M16 shallow water constituent to be locally enhanced by resonance. This shallow water effect has been included by adding an M16 constituent to the tidal elevation forcing and adjusting the M16 amplitude to generate peak flow discharges measured in the field. The computed flow discharge contains a high frequency oscillation similar to that observed in the field data. Since the hydrodynamic model replicates flow conditions accurately, it was used as part of the prediction tool for sediment dispersion modeling.