Hydrogeomorphological analysis and modelling for a comprehensive understanding of flash-flood damage processes: the 9 October 2018 event in northeastern Mallorca

In: Natural hazards and earth system sciences: NHESS, Band 20, Heft 8, S. 2195-2220

Open Access

Abstract

Abstract. A flash-flood event hit the northeastern part of
Mallorca on 9 October 2018, causing 13 casualties. Mallorca is
prone to catastrophic flash floods acting on a scenario of deep landscape
transformation caused by Mediterranean tourist resorts. As global change may
exacerbate devastating flash floods, analyses of catastrophic events are
crucial to support effective prevention and mitigation measures.
Field-based remote-sensing and modelling techniques were used in this study
to evaluate rainfall–runoff processes at the catchment scale linked to
hydrological modelling. Continuous streamflow monitoring data revealed a
peak discharge of 442 m3 s−1 with an unprecedented runoff
response. This exceptional behaviour triggered the natural disaster as a
combination of heavy rainfall (249 mm in 10 h), karstic features and land
cover disturbances in the Begura de Salma River catchment (23 km2).
Topography-based connectivity indices and geomorphic change detection were
used as rapid post-catastrophe decision-making tools, playing a key role
during the rescue search. These hydrogeomorphological precision techniques
were combined with the Copernicus Emergency Management Service and
"ground-based" damage assessment, which showed very accurately the
damage-driving factors in the village of Sant Llorenç des Cardassar. The
main challenges in the future are to readapt hydrological modelling to
global change scenarios, implement an early flash-flood warning system and
take adaptive and resilient measures on the catchment scale.