MORPHOLOGICAL RESILIENCE CAPACITY AND SEDIMENT BALANCE OF A BEACH RESTING ON PRECAMBRIAN BASEMENT IN SAN-PEDRO: HIGH-FREQUENCY ALTIMETRY MONITORING

In a context of significant coastal erosion along the San Pedro shoreline, this study looks at the morphological and sedimentary dynamics of a Precambrian bedrock beach affected by tidal cycle variations. The goal is to understand how the beach responds to marine forces, to measure sediment reshuffling, and to assess its resilience to erosion. To do this, high-frequency elevation monitoring was carried out on two contrasting beach profiles, one located in the hollow of the beach crescent and the other on its crest. This method made it possible to observe, at short intervals, topographic changes and sediment movements over several tidal phases. The results reveal a rapid alternation between accretion and erosion, with a general tendency for accretion during ebb and erosion during flood. The trough of the crescent profile retains more sediment than the crest, showing the influence of morphology on sediment dynamics. The amplitudes of reworking are lower in February than in April, reflecting an increased sensitivity of the coastal system during periods of strong wave action. Most monitored points show morphological resilience above 60%, although this capacity varies depending on the position on the foreshore and the intensity of the sea. In conclusion, despite relatively good short-term resilience, San Pedro beach remains subject to ongoing structural erosion. This study thus contributes to a better understanding of morphodynamic processes in Precambrian bedrock areas and provides useful information for preventive measures for vulnerable coastal areas.