Coastal paleokarst landforms: A morphometric approach via UAV for coastal management (Algarve, Portugal case study)

Abstract

Karst landscapes display remarkable morphological diversity and raise challenging management questions. Understanding karst processes is particularly relevant to the management of densely populated rocky coastlines, since sea-level rise influences the erosion rate of potentially hazardous landforms (e.g. sinkholes). Appropriate management strategies are needed to mitigate against property loss and economic impacts on actively eroding karst. Coastal management in these areas should be based on accurate and reproducible measurements of karst features to better understand and predict their behaviour. Due to their inherent instability and frequent inaccessibility, detailed morphometric studies of exposed coastal sinkholes are limited. We demonstrate the utility of using an unmanned aerial vehicle (UAV) to provide rapid and accurate analysis of spatial data on a large density of sinkholes that would otherwise be inaccessible. UAV data were post-processed and analysed using geographical information (GIS) tools to characterize both individual sinkholes and their spatial distribution patterns.Our study was carried out on the rocky coast of the central Algarve (southern Portugal). As stated in many other previous works, sinkholes spatial distribution is mainly controlled by the network of fractures in the host rock that was also observed in our study area. In addition, the geometric properties and their differences between the studied sites are controlled by weathering processes and synoptic conditions.This research emphasises the geomorphic hazard associated with karst landscapes and reinforces the need to include knowledge about these landforms and their vulnerability to sea-level rise in integrated coastal management plans.