Coastal karst geomorphosites at risk? A case study: the floods of 6–11 December 2004 in central-east Sardinia

Abstract

Extreme rainfall causing floods and great damage occurred in many areas of central-east Sardinia in the period 6–11 December 2004. A total of approximately 700 mm of rain was measured during this extreme event, with a maximum reaching 510 mm of rainfall in 1 day at the rain gauge of Villagrande (Ogliastra). During and immediately after the event all fluviokarstic canyons were activated for at least 1 week, reaching the highest water levels in at least 50 years and reversing great quantities of sediment-loaded water onto the coast and with important geomorphical modifications. There was public fear that serious damage to the natural resources would occur, such as the famous Cala Luna beach that was almost completely destroyed by the flooding of the Codula Ilune River and by the coinciding sea storm. The river, in fact, eroded the longshore bar (beach) and destroyed the small backshore lagoon. A monitoring study has been initiated in order to analyse the natural evolution of this littoral system and to define the resilience of this interesting geomorphosite. The observations have shown that the flood, albeit impacting negatively in the moments immediately after the disaster, almost completely restored the natural equilibrium of this coastal karst geo-ecosystem within a season.

Drowned karst landscape offshore the Apulian margin (Southern Adriatic Sea, Italy)

“…At present, there are no signs indicating any on-going karst activity, such as karst springs like those seen in similar contexts in other parts of the Mediterranean Sea (e.g., Cossu et al, 2007;Mijatović, 2007;De Waele, 2009). Hydrologic data acquired from inside the best developed doline, Oyster Pit, support this presumption since there is no anomaly with respect to the surrounding marine water mass (Fig.…”

Classification of karst springs for flash-flood-prone areas in western Turkey

“…Karst terrain are fragile and vulnerable to a variety of hazards , including flash floods due to heavy rainfall. They occur when intensive short-duration rainfall is recorded, such as 571 mm on 6 December 2004 in Sardinia, Italy (Cossu et al, 2007), or 200.5 mm on 12 September 2009 in Ayamama Creek, Istanbul, Turkey (Bacanli et al, 2011). Flash floods are intensified when heavy rainfall is combined with rapid snowmelt or man-made disasters (e.g.…”

Vulnerability assessment of Central-East Sardinia (Italy) to extreme rainfall events

“…Precipitation is here more intense than in other areas of Sardinia: major rain storms often follow dry periods and can succeed each other at short intervals and with the same epicentre, causing therefore serious environmental damage, deaths, the destruction of houses, land and dead cattle. The important geomorphic changes following the more recent floods, like modifications of the rivers bed morphology or movements of great quantities of sediment which have led to a visible landscape modification in many areas, have been studied in Cossu et al (2007) and in Cossu et al (2009b).…”