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TitleShort-term beach and shoreface evolution on a cuspate foreland observed with airborne topographic and bathymetric LiDAR
AuthorXhardé, R; Long, B F; Forbes, D L
SourceApplied LIDAR Techniques; by Pe'eri, S (ed.); Long, B (ed.); Journal of Coastal Research Special Issue, no. 62, 2011 p. 50-61, 62 6
Alt SeriesEarth Sciences Sector, Contribution Series 20090437
PublisherCoastal Education and Research Foundation
Mediapaper; on-line; digital
File formatpdf
ProvinceEastern offshore region
AreaGulf of St. Lawrence; Baie des Chaleurs
Lat/Long WENS -65.5000 -65.0000 48.0833 48.0000
Subjectsmarine geology; geophysics; coastal environment; coastal studies; shoreface deposits; shorelines; beaches; sediment transport; submarine transport; erosion; coastal erosion; topography; seafloor topography; seabottom topography; bathymetry; LiDAR
Illustrationslocation maps; tables; graphs; models
ProgramOffshore Geoscience, Program management
AbstractThis paper examines the short-term evolution of a cuspate foreland with diminished sediment supply in the western Gulf of St. Lawrence. Topographic light detection and ranging and airborne light detection and ranging bathymetry are used to provide an overall analysis of the foreland system at Paspébiac, Quebec, including high-resolution digital morphology of combined subaerial and subaqueous components, between 2003 and 2006. Results indicate large differences in coastal stability around the foreland. The western barrier exhibits a stable shoreline (net change = +0.3 m/y), a moderate beach slope (0.12 - 0.18), and no subtidal bar system. The morphodynamic response in this sector is influenced by jetties and alongshore variability and is related to beach planform readjustments to varying wave conditions. The eastern barrier has higher wave exposure, high erosion rates (<6.7 m/y), wave washover, and an intermediate barred-beach profile, with higher beach slopes (b = 0.16 - 0.24). The alongshore variability is controlled, at length scales of about 500 to 700 m, by differences in relaxation time between distal and proximal sections of the foreland. At shorter length scales (~100 - 500 m), alongshore variation is related to inner bar morphology, higher erosion rates being observed near rip channels or in the absence of an inner bar. Sand transport patterns reflect wave energy and approach and include a reversal in transport direction along the eastern barrier under storm waves from the SW. We show that, under declining sediment supply, sediment is being lost to a shoal and deep water off the tip of the foreland and erosion on the eastern barrier is not compensated by the slow accretion on the western side of the point.