Global wave-driven beach evolution; consequences for observation strategies

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Authors

Erwin Bergsma , Rafael Almar , Thierry Garlan, Elodie Kestenare

Abstract

It is an illusion to think that one can observe monthly beach behaviour with monthly surveys. Current coastal observation strategies restrict understanding of beach evolution, preventing effective risk mitigation. In this article, we quantify the global spatiotemporal scales of coastal wave changes, which are the known dominant driver of beach evolution. Consequences and recommendations for beach observation strategies are proposed and discussed. A global dominant time-scale of 30 days is found driving changes in average spatially correlated just over the synoptic 5 degrees regional scale (~550 km at the equator). Current observation-practices blind us to more than 80% of unresolved beach-change variability (shorter unresolved dynamics), leading to a large unacceptable knowledge gap. This reveals common surveying-schemes --with e.g. monthly or yearly time-interval-- limit our view on the actual beach evolution, and surprisingly, even for seasonal and inter-annual evolution. The global optimal surveying time-interval --maximizing the ratio gain/effort-- is found to be semi-annual, representative of the whole regional evolution. This clearly limits the use of traditional surveying strategies and promotes a paradigm shift in observational techniques towards a large-scale use (in space and time) of space-borne Earth Observation to address this challenge.

DOI

https://doi.org/10.31223/osf.io/eqfzr

Subjects

Civil and Environmental Engineering, Earth Sciences, Engineering, Life Sciences, Oceanography, Oceanography and Atmospheric Sciences and Meteorology, Physical Sciences and Mathematics

Keywords

Global, Shoreline, beach evolution, beach-memory, coastal vulnerability, surveying-frequency, wave climate

Dates

Published: 2020-06-12 15:20

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License

GNU Lesser General Public License (LGPL) 2.1

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