Abstracts
Abstract
Burley Beach (southeastern Lake Huron) exhibits a multi-barred shoreface, the long-term equilibrium morphology characteristic of many low angle, sandy beaches in the Canadian Great Lakes. During a single major storm, a new bar emerged 50-60 m offshore as an irregular trough-crest form, through differential erosion of an existing shore terrace. Emergence, bar growth and offshore migration were associated with: (a) an overall negative sediment balance in the inner surf zone initially (‑2.30 m3>/m beach width), but with a large positive sediment balance (+5.10 m3/m) subsequent to the storm peak and during the storm decay; (b) progradation of the beach step to produce a new shore terrace; and (c) offshore migration of the two outer bars to provide the accommodation space necessary for the new bar. The primary transport mechanisms accounting for emergence of the new bar, its growth and migration were: (a) the mean cross-shore currents (undertow), which always transported suspended sediment offshore; and (b) the onshore transport of suspended sediment by incident gravity wave frequencies early in the storm and subsequently by infragravity waves (at the storm peak and the decay period). The longshore transport of sediment was significant in terms of the gross transport, although the net result was only a small transport to the south-west (historic littoral transport direction). It did not cause bar initiation, but it may have supplied some of the sediment for bar growth. The primary mechanism for bar initiation and growth was the cross-shore displacement of sediment by wave-driven (oscillatory) transport and cross-shore mean currents (undertow).
Résumé
Émersion et migration d’une barre côtière : bilan sédimentaire et changements morphologiques d’une plage à barres multiples des Grands Lacs. La plage de Burley (sud-est du lac Huron) présente une avant-côte à barres multiples, état morphologique caractéristique de l’équilibre à long terme des plages sableuses à pente faible. Au cours d’un seul orage majeur, une nouvelle barre s’est développée à 50-60 m au large de la côte en forme de creux et crête irrégulière, suite à l’érosion d’une terrasse côtière. L’émersion, la croissance et la migration de la barre est attribuable à (a) un bilan sédimentaire négatif dans la zone interne du ressac (‑2,30 m3/m), mais à un bilan sédimentaire positif (+5,10 m3/m) durant l’apogée et la dissipation de l’orage, (b) l’exondation du gradin de plage pour générer une nouvelle terrasse côtière et (c) la migration de deux barres distales au large de la côte, laissant assez d’espace pour la mise en place d’une nouvelle barre. Les mécanismes de l’émersion, de la croissance et de la migration sont : (a) les contre-courants qui transportent les sédiments en suspension au large de la côte et (b) le transport vers la côte via la fréquence des vagues de gravité générées au début de l’orage et par les vagues d’infragravité subséquentes (au maximum de l’orage et durant sa dissipation). Le transport brut des sédiments est important, mais le résultat net correspond seulement à un léger transport vers le sud-ouest (direction historique du transit littoral). Ceci ne cause pas la création de la barre, mais peut contribuer aux apports sédimentaires nécessaires à sa croissance. Le mécanisme responsable de l’évolution des barres est le transport des sédiments par les vagues oscillatoires et les contre-courants.
Appendices
References
- Aagaard, T., Greenwood, B. and Nielsen, J., 2001. Bed level changes and megaripple migration on a barred beach. Journal of Coastal Research, Special Issue 34, p. 110-116.
- Aagaard, T. and Greenwood, B., 1994. Suspended sediment transport and the role of infragravity waves in a barred surf zone. Marine Geology, 118: 23-48.
- Aagaard, T. and Greenwood, B., 1995a. Suspended sediment transport and morphological response on a dissipative beach. Continental Shelf Research, 15: 1061-1086.
- Aagaard, T. and Greenwood, B., 1995b. Longshore and cross-shore suspended sediment transport at far infragravity frequencies in a barred environment. Continental Shelf Research, 15: 1235-1249.
- Aagaard, T. and Greenwood, B., 1999. Directionality of cross-shore sediment transport in the surf zone under high-energy conditions. Coastal Sediments ’99, American Society of Civil Engineers, New York, 16 p.
- Andrews, E., 1870. The North American Lakes considered as Chronometers of Post Glacial Time. Transactions of the Chicago Academy of Sciences, No. 2, p. 14.
- Angel, J.R. and Isard, S.A., 1997. An observational study of the influence of the Great Lakes on the speed and intensity of passing cyclones. Monthly Weather Review, 125: 2228-2237.
- Bauer, B.O. and Greenwood, B., 1990. Modification of a linear bar-trough system by a standing edge wave. Marine Geology, 92: 177-204.
- Carter, R.W.G., 1988. Coastal Environments: an introduction to the physical, ecological and cultural systems of coastlines. Academic Press, London, 617 p.
- Cooper, A.J., 1976. Quaternary Geology of the Grand Bend–Parkhill Area, Southern Ontario. Ontario Division of Mines, Sudbury, OFR5215, 119 p.
- Davidson-Arnott, R.G.D., 1988. Controls on formation of barred nearshore profiles. Geographical Review, 78: 185-193.
- Davidson-Arnott, R.G.D. and McDonald, R.A., 1980. Morphology and sedimentology of multiple bar systems, southern Georgian Bay, Ontario, p. 417-428. In S.B. McCann, ed., The Coastline of Canada. Geological Survey of Canada, Ottawa, Paper 80-10.
- Davis, R.A., Jr. and Fox, W.T., 1972a. Coastal processes and nearshore sand bars. Journal of Sedimentary Petrology, 42: 401-412.
- Davis, R.A., Jr. and Fox, W.T., 1972b. Four-dimensional model for beach and nearshore sedimentation. Journal of Geology, 80: 484-493.
- Desor, E., 1851. Report of the Lake Superior Land District, Part II. Edited by J.W. Foster and J.D. Whitney. United States General Land Office, 1866, 258 p.
- Dubois, R.N., 1973. Seasonal variation of a limnic beach. Geological Society of America Bulletin, 84: 1817-1824.
- Evans, O.F., 1940. The low and ball of the east shore of Lake Michigan. Journal of Geology, 48: 467-511.
- Gilbert, G.K., 1885. The topographic features of lake shores. United States Geological Survey, Reston, 5th Annual Report, 111 p.
- Gillie, R.D., 1974. The nearshore morphology of sand beaches on the Great Lakes shoreline of Southern Ontario. Unpublished M.Sc. Thesis, McMaster University, 140 p.
- Gillie, R.D., 1980. Barred nearshore profiles in Great Lakes research. Proceedings of the Canadian Coastal Conference, 14 p.
- Greenwood, B., 2003. Bars (Littoral), p. 40-43. In G.V. Middleton, ed., Encyclopaedia of Sedimentology. Kluwer Academic Publishers, Amsterdam.
- Greenwood, B., 2004. Bars, p. 120-129. In M. Schwartz, ed., Encyclopaedia of Coastal Science. Kluwer Academic Publishers, Amsterdam.
- Greenwood, B., Osborne, P.D., Bowen, A.J., Hazen, D.G. and Hay, A.E., 1991. Nearshore sediment flux and bottom boundary dynamics: the Canadian Coastal Sediment Transport Programme (C-COAST). In Proceedings of the 22nd International Conference of Coastal Engineering, Delft, Netherlands. American Society of Civil Engineers, New York, 14 p.
- Greenwood, B., 1987. Sediment balance and bar morphodynamics in a multiple bar system, Georgian Bay, Canada, p. 1119-1143. In V. Gardiner, ed., International Geomorphology. John Wiley and Sons, London.
- Greenwood, B. and Mittler, P.R., 1979. Structural indices of sediment transport in a straight wave-formed nearshore bar. Marine Geology, 32: 191-203.
- Greenwood, B. and Mittler, P.R., 1984. Sediment flux and equilibrium slopes in a barred nearshore. Marine Geology, 60: 79-98.
- Greenwood, B. and Davidson-Arnott, R.G.D., 1975. Marine bars and nearshore sedimentary processes, Kouchibouguac Bay, New Brunswick, Canada, p. 123-150. In J. Hails and A. Carr, eds., Nearshore Sediment Dynamics and Sedimentation. John Wiley and Sons, London.
- Greenwood, B. and Davidson-Arnott, R.G.D., 1979. Sedimentation and equilibrium in wave-formed bars: A review and case study. Canadian Journal of Earth Sciences, 16: 313-332.
- Hale, P.B. and McCann, S.B., 1982. Rhythmic topography in a mesotidal low-wave-energy environment. Journal of Sedimentary Petrology, 52: 415-429.
- Hands, E.H., 1976. Observations of barred coastal profiles under the influence of rising water levels, Eastern Lake Michigan, 1967-71. United States Army Corps of Engineers, Coastal Engineering Research Center, Technical Report 76-1, 113 p.
- Houser, C.A., 2004. Feedback mechanisms in the morphodynamics of multiple barred nearshores. Unpublished Ph.D. Thesis, University of Toronto, 217 p.
- Houser, C. and Greenwood, B., 2005. Profile response of a lacustrine multiple barred nearshore to a sequence of storm events. Geomorphology, 69: 118-137.
- Inman, D.L., Elwany, M.H.S. and Jenkins, S.A., 1993. Shorerise and bar-berm profiles on ocean beaches. Journal of Geophysical Research, 98: 18181-18199.
- Isard, S.A., Angel, J.R. and Van Dyke, G.T., 2000. Zones of origin for Great Lakes cyclones in North America, 1899-1996. Monthly Weather Review, 128: 474-485.
- Keranen, R., 1985. Wave-induced sandy shore formations and processes in Lek Oulujarvi, Finland. Nordia, 19: 1-58.
- Keulegan, G.H., 1948. An experimental study of submarine sand bars. Beach Erosion Board, Technical Report 3, 40 p.
- Kindle, E.M., 1936. Notes on shallow water structures. Journal of Geology, 44: 863-867.
- King, C.A.M., 1972. Beaches and Coasts. Edward Arnold, London, 470 p.
- Lippmann, T.L. and Holman, R.A., 1990. The spatial and temporal variability of sand bar morphology. Journal of Geophysical Research, 95: 11575-11590.
- Lippmann, T.L., Holman, R.A. and Hathaway, K.K., 1993. Episodic non-stationary behaviour of a two sand bar system at Duck, NC, USA. Journal of Coastal Research, Special Issue 15: 49-75.
- Lowe, R.L., 1989. Continuous bedload sampling, p. 91-93. In R.J. Seymour, ed., Nearshore Sediment Transport. Plenum Press, New York, 418 p.
- Miles, J.R., Russell, P.E., Ruessink, B.G. and Huntley, D.A., 2002. Field observations of the effect of shear waves on sediment suspension and transport. Continental Shelf Research, 22: 657-681.
- Miller, R.L., 1976. Role of vortices in surf zone prediction: sedimentation and wave forces, p. 92-114. In R.A. Davis, Jr. and R.L. Ethington, eds., Beach and Nearshore Sedimentation. Society of Economic Paleontologists and Mineralogists, Tulsa, Special Publication 24.
- Osborne, P.D. and Greenwood, B. 1992. Frequency dependent cross-shore suspended sediment transport 2: a barred shoreface, Bluewater Beach, Ontario, Canada. Marine Geology, 106: 25-51.
- Owens, E.H., 1977. Temporal variations in beach and nearshore dynamics. Journal of Sedimentary Petrology, 47: 168-190.
- Permanand-Schwartz, A., 2003. Hydrodynamics, suspended sediment transport and morphodynamics associated with a nearshore bar, Burley Beach, Ontario, Canada. Unpublished M.Sc. Thesis, University of Toronto, 189 p.
- Ruessink, B.G. and Terwindt, J.H.J., 2000. The behaviour of nearshore sand bars on a timescale of years: a conceptual model. Marine Geology, 163: 289-302.
- Russell, I.C., 1885. Geological history of Lake Lahontan. United States Geological Survey, Reston, Monograph II, p. 92-93.
- Saylor, J.H. and Hands, E.B., 1970. Properties of longshore bars in the Great Lakes. In Proceedings of the 12th International Coastal Engineering Conference. American Society of Civil Engineers, New York, 15 p.
- Shand, R.D., 2003. Relationships between episodes of bar switching, cross-shore bar migration and outer bar degeneration at Wanganui, New Zealand. Journal of Coastal Research, 19: 157-170.
- Shepard, F.P., 1950. Longshore bars and longshore troughs. United States Army Corps of Engineers, Beach Erosion Board Technical Memorandum 15, 32 p.
- Southgate, H.N. and Möller, I., 2000. Fractal properties of coastal profile evolution at Duck, North Carolina. Journal of Geophysical Research, 105: 11489-11507.
- Sternberg, R.W., Shi, N.C. and Downing, J.P., 1989. Suspended sediment measurements. Continuous measurements of suspended sediment, p. 231-257. In R.J. Seymour, ed., Nearshore Sediment Transport. Plenum Press, New York, 418 p.
- Thornton, E.B., Humiston, R.T. and Birkemeier, W., 1996. Bar/trough generation on a natural beach. Journal of Geophysical Research, 101: 12097-12110.
- Whittlesey, C., 1896. Freshwater glacial drift of the northwestern States. Smithsonian Contribution 197, p. 17.
- Wijnberg, K.M., 1995. Morphologic Behaviour of a Barred Coast over a Period of Decades. Ph.D. Thesis, Proefschrift Universiteit Utrecht, 245 p.
- Wijnberg, K.M. and Kroon, A., 2002. Barred beaches. Geomorphology, 48: 103-120.
- Wright, L.D., Chappell, J., Thom, B.G., Bradshaw, M.P. and Cowell, P., 1979. Morphodynamics of reflective and dissipative beach and inshore systems, southern Australia. Marine Geology, 32: 105-140.
- Wright, L.D. and Short, A.D., 1984. Morphodynamic variability of surf zones and beaches: a synthesis. Marine Geology, 56: 93-118.
- Zenkovitch, V.P., 1967. Processes of Coastal Development. Oliver and Boyd, London, 738 p.