Application of precision technologies in geomorphology: analysis of the flash flood occurred in Sant Llorenç des Cardassar, Mallorca, October 2018

Abstract

<p>A flash-flood event hit in the 9th October 2018 the northeastern part of Mallorca Island, causing 13 casualties. As global change may exacerbate devastating flash floods, comprehensive analyses of catastrophic events are crucial to support effective prevention and mitigation measures. Field-based, remote-sense and modelling techniques were used to evaluate rainfall-runoff processes at catchment scale linked to hydrological modelling. Continuous streamflow monitoring data revealed a peak discharge 442 m<sup>3</sup> s<sup>−1</sup> with an unprecedented runoff response (lag time, 15’). This very flashy behaviour triggered the natural disaster as a combination of heavy rainfall (246 mm in 10 h), karstic features and land cover disturbances in the Begura de Saumà River catchment (i.e., 23 km<sup>2</sup>). Topography-based connectivity index and geomorphic change detection were used as a rapid post-catastrophe decision-making tool, playing a key role during the rescue searching tasks. These hydrogeomorphological precision techniques were also applied in combination with Copernicus EMS and ground-based damage assessment illustrating with high accuracy the damage driving factors in the village of Sant Llorenç des Cardassar.  The incorporation of hydrogeomorphological precision tools during Emergency post-catastrophe operational has been revealed as a powerful tool. Then, the simple application of a geomorphometric index from easy-access LiDAR-based topographic data resulted in a rapid identification of deposition zones in the different compartments of a catchment helping in the search and rescue of missing persons. In addition, the evaluation of landforms signature by using UAVs effectively quantified the sediment deposits generated by the flash-flood and/or mobilised by the Emergency operational during the rescue searching tasks.</p><p><em>This work was supported by the research project CGL2017-88200-R “Functional hydrological and sediment connectivity at Mediterranean catchments: global change scenarios –MEDhyCON2” funded by the Spanish Ministry of Science, Innovation and Universities, the Spanish Agency of Research (AEI) and the European Regional Development Funds (ERDF)</em></p>