Geomorphological typology of cliff-foreshore continuum using a statistical approach: Application to the rocky coasts of Charente-Maritime, France

This study proposes a new geomorphological typology of cliff-foreshore continuum in Charente-Maritime, by integrating foreshore characteristics into a statistical approach. The aim is to assess the contribution of often-neglected components to the characterization of rocky cliff coasts. Accordingly, the study replaces expert-based typologies with an objective methodology combining Factor Analysis of Mixed Data (FAMD) and Hierarchical Clustering Analysis (HCA). The analysis is based on a systematic sampling strategy, with 490 points spaced at 100 m intervals, and multi-source datasets including field work, LiDAR data, CHARM database and Litto3D database. Seven key variables were considered: lithology, topography (including height, slope, and aspect), structure (dip angle) of the cliffs and foreshore properties (nature and slope). The results identify five distinct groups of cliff-foreshore continuum. Four variables account for 80 % of the cumulative explained variance: lithology (32 %), nature of foreshore (26 %), cliff slope (16 %), and dip angle (8 %). The resulting typology displays strong spatial coherence, with each cliff group showing a contiguous geographical distribution. Comparison with a previous typology using a confusion matrix indicates 75 % similarity, partially validating the approach, although some discrepancies persist, notably regarding the identification of a potential sixth group. Overall, this study demonstrates the relevance of a systemic cliff-foreshore and statistically based approach to the characterization of rocky coasts.