Groundwater Floodings, Storm Surges and Wind Direction: a silent threat in coastal areas

  • BLANCO-CORONAS, ANGELA (UNIVERSITY OF GRANADA)
  • DUQUE, CARLOS (UNIVERSITY OF GRANADA)
  • LÓPEZ-CHICANO, MANUEL (UNIVERSITY OF GRANADA)
  • CALVACHE, MARIA LUISA (UNIVERSITY OF GRANADA)

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Global warming is expected to lead to rising mean sea level, as well as alter wind-wave dynamics (Hemer et al., 2013) and trigger more frequent and intense storm surges (Little et al., 2015). These phenomena will amplify the magnitude and frequency of extreme episodic rises of sea level and coastal flooding, resulting in increased shoreline erosion (Vitousek et al., 2017) and significant damage to coastal ecosystems (Little et all., 2015). Storm surges travel toward the coast as shallow water waves (Idier et al., 2019), leading to the accumulation of seawater mass near the shore. As seawater levels rise, groundwater in low-lying areas can exceed the land surface, resulting in groundwater flooding. These events are often wrongly interpreted with surface water flooding, due to the complex nature of hydrodynamics in coastal aquifers. The southeastern coast of Spain is highly exposed to powerful storms that can have a significant impact on both natural and urban areas (Molina et al., 2019). The present study focused on the specific case of the Motril (South-East Spain), where there was an increment in the frequency of flooding events over the past decade. Groundwater level data was obtained from 3 research wells near the shoreline and compared to different climate and oceanographic series to understand their interdependencies during coastal floodings. In addition, limnimetric level data was measured to study changes in the hydrodynamics of a wetland located a few hundred meters from the coastline (La Charca de Suárez) during floodings. During the study period, various types of flooding were observed during strong winds. Several floods were caused by a rise in the groundwater level, occurring without precipitation or marine flooding. Time series analysis revealed that the wind direction was a key factor over the piezometric levels as well as the direction of the shoreline.