ABSTRACT

Díaz-Cuevas, P.; Prieto-Campos, A.; Fraile-Jurado, P.; Ojeda-Zújar, J., and Álvarez-Francoso, J.I., 2020. Shoreline "proxies" evaluation for mid-term erosion rates calculation in mesotidal and microtidal beaches (Andalusia, Spain). In: Malvárez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 1062–1066. Coconut Creek (Florida), ISSN 0749-0208.

Coastal erosion is closely linked with the concept of sedimentary balance and traditionally is considered a relevant variable for the assessment of changes related to loss of sediments (usually computed as shoreline retreat). Nevertheless, coastal erosion can be examined through a wide variety of methodologies, each of which has its own characteristics and aims. The 3D (volumetric) method is currently the most accurate, but the lack of historical data series makes difficult a mid/long-term analysis of the phenomenon, so most studies rely on one-dimensional or bi-dimensional analysis based on aerial photographs and the use of indirect indicators (proxies), such as shoreline oscillation, using generally, the mark left by the high water line and, less frequently the backshore/foredune contact. This paper examines different proxies for the analysis of erosion rates in the mid-term in the Andalusian coast, which are exposed to different morphodynamics processes (one is in the Atlantic coast and the other one in the Mediterranean coast). In order to do this, different proxies have been digitized at a 1:2500 scale, and the erosion rates have been calculated for the period 1977-2013. The results suggest that, in general, the use of the backshore/foredune proxy is consistent, especially in Atlantic beaches (mesotidal), while the high water line proxy is used in Mediterranean beaches (microtidal), as long as the morhodynamics conditions remain homogeneous (summer season) for the dates of ortophotographies. However, the erosion rates calculated with proxies in this way should be taken with caution and supported by additional evidence for adequate interpretation.

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