MORPHODYNAMIC OF BEACH SCARPS ON A MACROTIDAL COAST DURING EXCEPTIONAL WATER LEVEL EVENTS (NORMANDY, FRANCE)

Yoann Bonte, Franck Levoy

Abstract


Although there are numerous studies on the morphology and physical processes affecting the dune's scarp and many conceptual models describing beach scarps on microtidal and mesotidal environments (Sunamura, 1985a ; Short,1999), really quantitative informations about the beach scarp formation is lacking, especially along tidal environments where the tide controls the level of wave attack. However, Sherman and Nordstrom(1985) give a qualitative description of beach scarp formations and evolution based on field observations but without data set. The coast of Calvados (Normandy, France) is a fine example of a macrotidal coast, where beach scarps have been often observed. Along macrotidal beaches, the formation of a berm is classically observed during fair weather conditions which contribute to stabilize the coastline. During stormy conditions, the low atmosphere pressure, short waves and onshore winds cause an increase of the water level, which during spring tides, increases the high tide water level time action. Consequently, the natural berm protecting the dune foot, or sometimes a seawall foot, is threatened by erosion and often destroyed. The goal of this study is to quantify the beach scarp destruction (foot and crest scarp retreat speed, eroded volume...) in relation with the hydraulic and morphologic local conditions.

Keywords


beach scarp; erosion; macrotidal; swash

References


Sherman, D.J. and Nordstrom, K.F. 1985. Berach scarps. Z. Für Geomorphologie, 29-2. 139-152.

Short, A.D. (editor), 1999. Handbook of Beaches and Shoreface Morphodynamics, Wilez and Sons, Chichester.

Sunamura, T., 1985 in Horikawa, K. 1988. Nearshore Dynamics and Coastal Processes, Theory, Measurment, and Predictive Models, University of Tokyo Press.


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