As the product of a variety of sediment sources and sedimentation (and re‐sedimentation) and erosion processes, the geomorphology and sedimentology of carbonate slopes are highly variable. The purpose of this study is to describe sub‐bottom profiles and side‐scan sonar, multibeam and optical data acquired by an autonomous underwater vehicle to explore variability in geomorphological and sedimentological character of the present‐day platform‐marginal, uppermost slope environments (< 240 m water depth) on the north, open‐ocean facing flank of Little Bahama Bank, Bahamas. Although at time scales of greater than 100 ka this margin is progradational, the data illustrate a complex juxtaposition of erosional and depositional processes and features. Erosion is evidenced by two prominent escarpments (70 m and 120 m) that expose eroded, bedded rocky outcrops. These escarpments are interpreted to represent relict features, related to past sea‐level positions, although they still may be shedding debris. Aside from erosional remnants, sedimentation and active transport is indicated by several features, including active bedforms (especially above the 70 m escarpment, but ripples occur to depths of ca 200 m), several mass transport complexes that overlie and cover the lower escarpment, gravity flow deposits and rare slump features. Similarly, a thick (up to 20 m) onlapping sediment wedge, interpreted to be Holocene in age, suggests lateral accretion of the slope by more than 75 m in this period. Data illustrate that this open‐ocean margin is distinct from windward margins in the Bahamas, which typically include near‐vertical walls of erosion or bypass, flanked downdip by rubble and talus, and leeward margins, which have onlapping muddy wedges, but that lack marked terraces or escarpments. Collectively, the results provide perspectives into the nature and controls on complex geomorphological patterns of erosion and deposition in Holocene uppermost slope systems, concepts potentially applicable to ancient analogues.

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Selection of cable routes and wind turbine site assessments for offshore energy projects in the often-complex geology of the North American Atlantic coast entails very high risks for developers as well as state agencies: limited desktop data, patchy distribution of critical or sensitive habitats, and use conflicts, are a sampling of the risks encountered. The costs required to conduct multi-disciplined geophysical spreads including weather delays during marine mammal transit windows does not support exploring multiple or alternative routes. A novel approach was developed by Fugro and INSPIRE Environmental to reduce the risks and costs of required geophysical and benthic assessment surveys for offshore wind projects. Collection of field data is required by the Bureau of Ocean Energy Management (BOEM) as part of the Site Assessment Plan (SAP) for geophysical and biological characterization in offshore wind development. Collection of Sediment Profile Imagery (SPI) and Plan View (PV) imagery was integrated with multibeam echosounder (MBES) acoustic data collection to optimize route selection, provide ground-truth of acoustic data, and characterize benthic habitats in survey campaigns at three offshore wind projects. The SPI/PV data were downloaded daily and combined with on-board processed MBES data to provide near real-time guidance for optimizing survey operations. BOEM requires the mapping of sensitive habitats such as deepwater corals, eelgrass beds, and hard bottom environments including bedrock, boulder and cobble habitats as well as habitat characterization for a full benthic assessment. The data presented from these three projects using the Forward Scouting approach illustrates the utility of rapid data acquisition and interpretation to support project-critical acoustic surveys. The SPI/PV data will be presented in an innovative visualization that integrates the profile and plan view imagery and processed MBES data. The visualization of the ground-truthed and benthic assessment data with landscape-scale seabed features has provided valuable decision-making support for archeological, benthic, fisheries, and engineering assessments. These combined technologies demonstrated the success of a collaborative approach to cable route and site characterization and led to development of the Forward Scouting approach to further reduce risk to schedules and assets, reduce site investigation costs, and incorporate multi-discipline (engineering and environmental) site data during early stages of project planning that is beneficial to stake-holder engagement activities. Cable routing and site assessment is optimized when engineering and restricted-habitat constraints are minimized prior to full geophysical and geotechnical (G&G) survey operations with large assets. The SPI/PV Forward Scouting survey team can be deployed with high-frequency (&gt;200 kHz) acoustic reconnaissance tools on small vessels that do not require permits or protected species observers (PSOs). The acoustic data collection for reconnaissance can utilize wider swath data retention without the requirement to meet International Hydrographic Organization standards and ‘sweep’ the proposed cable routes prior to defining the accepted centerline for full spread surveys. The SPI/PV photographic data provides ground-truth for the acoustic reconnaissance and if collected along the accepted centerline prior to demobilization will also provide baseline data acceptable for benthic assessment. The Forward Scouting approach offers the offshore wind industry critical advantages in cost and time by utilizing seasonal survey windows often inaccessible to the full-complement of geophysical equipment or vessels and reducing the scope of survey plans based on desktop data review. The potential for Forward Scouting is optimized with close collaboration between geophysical and SPI/PV providers.

Offshore wind developers obtain extensive geophysical, geotechnical, and habitat data during Site Characterization activities. Integration and delivery of this information to a diverse group of stakeholders and Government agencies is required. We present an integrated benthic habitat mapping approach tailored to regional geology and ground conditions and discuss how various data was utilized to deliver multiple components of the permitting process. Multiple data sets were integrated and presented via a web-based GIS platform to aid delivery, visualization, and communication. Our unified approach to benthic habitat mapping and delivery of products to stakeholders was instrumental in successfully coalescing multiple performers to develop their individual deliverables in a cohesive and rapid manner. This approach reduced risk to schedule and budget, without sacrificing data density or quality. Four annual (2019–2022) benthic surveys were acquired to support Site Characterization and subsequent permitting processes. High-Resolution Geophysical data were collected concomitantly with the 2020 benthic survey data and used to refine subsequent 2021 and 2022 benthic survey designs. Benthic survey data consisted of grab sample tests (grain size), macrofaunal taxonomy, sediment profile and plan view imagery (SPI-PV), video imagery from each grab station, and towed video transects. Acoustic data products were processed and interpreted to create polygons of seafloor sediment coverage over the ASOW study area and ground-truthed with physical sampling, video, and digital still imagery to refine and validate acoustic data into a mappable model of essential fish and benthic habitats. Seafloor morphology and seabed sediment interpretations were coalesced into a benthic habitat model that displayed substrates consisting mostly of mobile sand sheets, with interspersed areas of gravelly sand and discrete patches of gravel. Overlying the substrate model was a range of benthic features and morphologies, including sand ridges, sand waves, megaripples, ripples, areas of depressional marks, hummocky seafloor, interbedded surficial sediments, irregular seafloor, and localized relief features. From these data, classified maps of Coastal Marine Ecological Standard (CMECS) substrates and fish habitats were made. Additional CMECS classification of benthic biotic components were mapped, showing the taxonomic communities that are present in each substrate. Seabed sediment modeling and morphological trends were dynamically studied and compiled into an interpreted and GIS-friendly dataset that enabled rapid online transfer to subject matter experts tasked with quantifying the benthic ecosystem across the development area. The methods and modeling that were produced by expert refinement of geophysical data to reflect the physically observed habitat structures allowed for dynamic minimum mapping unit variability while also isolating and identifying key areas of interest for benthic researchers and regulators. This mapping process led to an efficient and unified approach for all teams, saving project time and expense.

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