Understanding coastal impacts by nearshore wave farms using a phase-resolving wave model

When extracting wave energy, arrays of wave energy converters (or wave farms) may alter surrounding wave and flow fields. This paper studies the modification of hydrodynamic processes at the coastline induced by nearshore wave farms using a recently developed phase-resolving wave-flow model. Changes to nearshore hydrodynamics were assessed for various farm configurations of submerged point-absorbers positioned 1–3 km offshore that were subject to realistic sea-states. In the lee of the farms, wave heights were attenuated and onshore directed flows were generated that extended several hundred meters shoreward but did not impinge the coast. For scenarios in which the wave shadow extended to the coast, the nearshore wave height and setup were reduced resulting in longshore pressure gradients driving longshore flows that converged in the lee of the farms. Changes were largest for compact farms at smaller offshore distances, and conversely, were significantly smaller for wider spaced arrays at greater offshore distances. Based on a bulk longshore sediment transport formulation, the converging flow patterns indicate conditions favourable for the accumulation of sediment in the direct lee and divergence of sediments at locations up/down coast from the farm, suggesting a reorientation of the shoreline in response to the wave farm configurations considered.