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

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.

Impact‐Based Forecasting for Pluvial Floods

“…With less than 5 min computation time of the entire model chain on a standard desktop PC for a 5 km 2 urban catchment, warnings based on the provided impact forecasts could still be issued with a few minutes lead time to guide ad‐hoc risk reduction measures and damage containment, which has not been possible with previous approaches. Apart from its use as part of an early warning system, the provided model outputs can provide important information for the immediate emergency response, which can help to improve capacity planning for emergency responders and support search and rescue operations (Estrany et al., 2020). Comparing the results of the ANN model with a physically based coupled 2D hydraulic surface‐subsurface model for an actual pluvial event, we show that the deviations are only minor and hardly affect the performance of the subsequent models, namely the contaminant transport and damage model.…”

A Survey of Remote Sensing and Geographic Information System Applications for Flash Floods

“…Ground elevation, inundation depths, ground height, inundation level, latitude, sediment, rainfall Joan Estrany et al [33] The meteorological, hydrological, geomorphological, damage, and risk data analyses were integrated to damage assessment based on field-based remote sensing and modeling.…”

“…The analysis of the disaster area after the occurrence of flash floods can better provide suggestions for regional development, flood prevention, and disaster reduction [33,86]. Table 3 lists four representative studies about the impact of flash flood assessment, which describe the impact of flash floods in terms of vegetation, agricultural products, topographic changes, and land cover.…”

“…Typically, due to the remote location of the flash flood area and the harsh weather, it is difficult to arrive at the scene to analyze the behavior of mountain torrents. In GIS environments, the most commonly used method involves drawing hazard maps of flash floods using hydrological and hydrodynamic models [30][31][32][33]. Table 4 lists five articles that use hydrological models or hydraulic models to map flash flood hazards.…”

“…The current research on flash floods mainly involves flash flood forecasting [14][15][16][17][18][19][20][21], flash flood disaster impact assessments [22][23][24][25], identifications of flash flood hazard areas [26][27][28][29][30][31][32][33][34][35], flash flood susceptibility assessments [36][37][38][39], and flash flood risk assessments [40][41][42][43][44][45]. Therefore, the motivation for our study is to comprehensively review the major areas related to the application of remote sensing and GIS technologies to flash flood disasters.…”