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In this investigation, instrumented mobile platforms are used to spatially map the turbulent flows in Grand Passage, one of the Bay of Fundy's more energetic tidal channels in Nova Scotia, Canada. The aim is to characterize the flow around the PLAT-I floating tidal energy platform developed by Sustainable Marine Energy Canada (SMEC). GPS-tracked surface drifters equipped with fast-sampling acoustic Doppler current profilers (ADCPs) provide turbulence-resolving vertical profiles of velocity and turbulent kinetic energy dissipation rate along drifter trajectories, while vessel-mounted ADCP transects complement the mean flow velocity measurements. These data are used to construct tridimensional quasi-synoptic maps of mean velocities and turbulence parameters for several stages of the tide around PLAT-I's location including peak ebb and flood currents. The data set includes measurements under natural flow conditions, and while the turbines installed on PLAT-I were both not operational and operational. The measurement techniques and resulting maps successfully capture the spatial and temporal structure of the flow for unsteady conditions for various tidal conditions. The combined wake of the four 6.3 m operational PLAT-I turbines was measured for a single tidal stage. Closer to the turbines, the vertical extent of the wake is about 6 m (approximately one turbine diameter), increasing with distance downstream, while the maximum observed velocity deficit is 26% relative to not operating conditions, decreasing with distance downstream. [ABSTRACT FROM AUTHOR]

Field observations are presented of the morphological evolution of beach cusps on a 1:10 slope, megatidal (8–12 m range), mixed sand-gravel beach at the head of the Bay of Fundy, Nova Scotia. Cusps had mean wavelengths of 3–6 m and displayed pronounced horn/bay sediment size segregation, with sand-sized material in the bays and gravel-sized material in the horns. Cusp occurrence was limited to the upper third of the beach face. Shoreline position during the tidal cycle was estimated at three minute intervals from time-averaged video imagery. Three cusp events are examined in detail, two exhibiting pronounced topographic relief, and the third demonstrating sensitivity of the rate of cusp evolution to the beach surface grain size distribution. Forcing conditions were weak, with significant offshore wave heights of 10–20 cm and peak periods of 4–7 s. Relict cusp morphology was inundated with the rising tide and destroyed or reworked during high tide. New cusps formed during the falling tide through a combination of accretion at the horns and erosion in the embayments. Timescales of growth and decay were short, ranging from 10 to 30 min. The location and dynamics of cusp horns appeared to depend on the high water line and its location relative to any pre-existing cusp morphology. The apparent sensitivity of cusp formation timescales to the local grain size distribution suggests that size segregation is intrinsic to the process of mixed sand-gravel cusp evolution. • Timescales of initial beach cusp emergence were of the order of 10 min. • The very broad grain-size distribution affects cusp evolution timescale. • Positions of emergent cusps were influenced by pre-existing morphology. • Cusp evolution was modulated by the 10-m range tide. [ABSTRACT FROM AUTHOR]