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TitleModelled nearshore sediment transport in open-water conditions, central north shore of Prince Edward Island, Canada
AuthorManson, G K; Davidson-Arnott, R G D; Forbes, D L
SourceCanadian Journal of Earth Sciences 2016 p. 101-118,
Alt SeriesEarth Sciences Sector, Contribution Series 20140480
PublisherNRC Research Press
Mediapaper; on-line; digital
File formatpdf
ProvinceEastern offshore region
AreaGulf of St. Lawrence
Lat/Long WENS -64.0000 -46.0000 62.0000 48.0000
Subjectsmarine geology; sedimentology; regional geology; sediment distribution; sediment transport; marine sediments; marine environments; hydrodynamics; transgressions; transport mechanisms; nearshore currents; tidal currents
Illustrationslocation maps; graphs
ProgramCoastal Infrastructure, Climate Change Geoscience
AbstractThe central north shore of Prince Edward Island comprises embayments separated by subtle headlands that may constrain nearshore sediment transport. The study area includes two such embayments informally known as Brackley and Tracadie bights, both of which are sand-rich onshore and sand-starved between 20 and 50mwater depth. Storm winds and waves from the northwest and northeast are common in autumn and winter. The hydrodynamic model Delft3D is used to simulate waves, currents, water levels, and sediment transport in Brackley and Tracadie bights during 23 autumn seasons between 1955 and 2005. When compared with wave and current measurements from a field experiment in the autumn of 1999, the model successfully simulates conditions during storms and fair-weather periods. Results from the simulations show that, in autumn, the weighted mean direction of transport is to the southeast (133°). Bedload transport is directed onshore to the south (170°), and suspended load is directed offshore to the northeast (67°). When aggregated over the 23 seasons, transport magnitudes and directions differ between Brackley and Tracadie bights. Rates of transport are higher in Tracadie Bight and directed more to the east. During individual storms, transport is dependent on the storm wind and wave direction. Most transport occurs in bed load, and deposition occurs at the shoreline, with erosion offshore. The patterns of bed load and suspended load suggest a mechanism for the landward migration of this shoreline during transgression, and may explain the existence of the sand-starved zone offshore.
Summary(Plain Language Summary, not published)
The movement of sediment is a primary control of rates of coastal change, and is important in consideration of how rates of change may evolve in a changing climate. The movement can occur through bedload transport in which sediment rolls and hops along the seabed, or through suspended load transport in which sediment becomes entrained in currents above the seabed. To understand mean present day transport conditions, sediment transport during 23 autumn seasons between 1955 and 2005 is modelled using Delft3D software. Modelling results indicate that bedload transport is onshore to the south while suspended load transport is offshore to the northeast. When considered together, a conceptual model in which sediment is moved onshore due to rising relative sea level and storms can be refined to explain the distribution of offshore sediments in the study area.