Quantification of cliff retreat in coastal Quaternary sediments using anatomical changes in exposed tree roots

Abstract

Sea cliffs represent 80% of the world's coasts and can be found virtually in all types of morphogenetic environments. Most studies on rocky environments focused on the impacts of modern sea level rise on cliff stability derived from sequential surveys, direct measurements or erosional features in anthropogenic structures. In this study, we explore the potential of dendrogeomorphic techniques to quantify multidecadal changes in coastal environments on Porquerolles Island (France). We sampled a total of 56 cross‐sections from 16 Pinus halepensis Mill. roots growing on former alluvial deposits and on sandy‐gravelly cliffs to quantify mean annual cliff retreat rates as well as changes in cliff geometry. Anatomical changes in roots have been used successfully in the past to quantify continuous denudation rates on slopes, channel incision and gullying processes but the approach has not been used so far in a coastal cliff context. At Porquerolles Island, reconstructed rates of cliff retreat cover 30–40 years and show average erosion rates between 0.6 and 3.9 cm yr−1 (average: 2.1 cm yr−1). Highest rates are observed at Pointe de la Tufière (2.6–3.9 cm yr−1), a small rock promontory that is more exposed to wave and storm surges than the remainder of the study area. By contrast, lower erosion rates are recorded at cliffs protected by the La Courtade pocket beach (0.6–1.9 cm yr−1). This contribution demonstrates that dendrogeomorphic analyses of roots clearly have a significant potential and that they are a powerful tool for the quantification of multidecadal rates of cliff retreat in areas where measurements of past erosion are lacking. More specifically, the approach also has clear advantages over the shorter time series obtained with repeat monitoring (e.g. terrestrial laser scanning, sensors, erosion pins) or over longer, but more coarsely resolved records obtained from aerial photographs or radio‐nuclides. © 2018 John Wiley & Sons, Ltd.

Avaliação De Curto Prazo Da Retração Das Falésias De Tibau Do Sul-Rn

“…No geral, a taxa média de retração para o litoral do Município de Tibau do Sul entre 2003 e 2013 foi de -0,442 m/ano, assinalando que 37% de linhas de costa distintas por falésias marinhas esteve submetida a erosão. Em comparação a alguns estudos recentes, similares na abordagem metodológica e nas análises de curto prazo temporal, destaca-se como taxa de recuo expressivamente alta, a exemplo da costa sul e central da Califórnia (EUA) com -0,044 m/ano (YOUNG, 2018), e de setores da costa francesa com recuo de -0,060m/ano a -0,390 m/ano (LOPEZ-SAEZ et al, 2018).…”

Cliff Retreat Rates Associated with a Low-Level Radioactive Waste Disposal Facility in Los Alamos, New Mexico, USA

“…Cliff retreat rates in coastal regions are well characterized and studied in part due to higher population density [3][4][5][6][7], but cliff retreat rates in arid environments are less thoroughly studied [8,9]. Existing and proposed waste disposal facility locations in the southwestern and western U.S.…”

Model Test Study on Wave-induced Erosion on Gravelly Soil Bank

“…Over the years, long-term measurement data on sea cliff erosion distances have accumulated (Young et al, 2020). Therefore, most studies on coastal wave erosion focus on establishing the time equation of the sea cliff erosion rate, which primarily includes the fixed value method (Lopez-Saez et al 2018) and probability methods (Muñoz et al 2020). Some studies, such as Huppert et al (2020), that focused on studying the erosion mechanism of wave erosion coast found a positive correlation between wave energy and rocky sea cliff erosion and 4 constructed an energy prediction equation for sea cliff erosion.…”