Flash Flood Events along the West Mediterranean Coasts: Inundations of Urbanized Areas Conditioned by Anthropic Impacts

Abstract

Flash floods represent one of the natural hazards that causes the greatest number of victims in the Mediterranean area. These processes occur by short and intense rainfall affecting limited areas of a few square kilometers, with rapid hydrological responses. Among the causes of the flood frequency increase in the last decades are the effects of the urban expansion in areas of fluvial pertinence and climatic change, namely the interaction between anthropogenic landforms and hydro-geomorphological dynamics. In this paper the authors show a comparison between flood events with very similar weather-hydrological characteristics and the ground effects occurred in coastal areas of three regions located at the top of a triangle in the Ligurian Sea, namely Liguria, Tuscany and Sardinia. With respect to the meteorological-hydrological hazard, it should be noted that the events analyzed occurred during autumn, in the conditions of a storm system triggered by cyclogenesis on the Genoa Gulf or by the extra-tropical cyclone Cleopatra. The “flash floods” damage recorded in the inhabited areas is due to the vulnerability of the elements at risk in the fluvio-coastal plains examined. There are numerous anthropogenic forcings that have influenced the hydro-geomorphological dynamics and that have led to an increase in risk conditions.

Reconstrucción post-evento del flash-flood del 1 de septiembre de 2021 en Les Cases d’Alcanar (Tarragona)

“…En algunas ocasiones estos fenómenos alcanzan zonas situadas más al interior, generalmente al dorso de relieves montañosos paralelos a la costa, como la Cordillera Prelitoral (Llasat et al, 2003;Ruiz-Bellet et al, 2015;Martin-Vide y Llasat, 2018). Por los altos caudales y el reducido tiempo de respuesta, las crecidas de tipo flash-flood son muy peligrosas comportando habitualmente inundaciones con un gran número de pérdidas de vidas humanas, destrucción de infraestructuras y bienes e interrupción de servicios (Barredo, 2009;Gaume et al, 2009;Faccini et al, 2021).…”

Geo-Hydrological Events and Temporal Trends in CAPE and TCWV over the Main Cities Facing the Mediterranean Sea in the Period 1979–2018

“…These meteorological conditions cause rainfall that may occur diffusively and persistently, or be concentrated and intense, have thunderstorms [21] and windstorms. The consequent floods or flash floods often cause much damage [22,23] affecting a large portion of the population.…”

Tropical disturbances in the southeastern North Atlantic. State of the art and future prospects

“…In the middle latitudes, rain and wind events are linked to the arrival of storms or extratropical cyclones. Although, in general, they do not have a great impact, the formation of an Isolated Depression at High Levels (DANA) can produce episodes of floods, which are more serious in coastal areas, especially in spaces with mountains near the sea, such as large sectors of the Mediterranean (Llasat et al, 2010;Faccini et al, 2021). This is the case of the Spanish Mediterranean coast, the Ligurian coast in Italy, the French Côte d'Azur or the archipelagos of Madeira and the Canary Islands.…”