Flash flood event recorded in caves: the case of Supramonte (Sardinia, Italy)

The high dynamism of karst aquifers makes them suscepti ble to short-term climate changes. One of the predictedconsequences of global climate change is the increase of the extreme events recurrence. To improve the understanding of its eff ects on the complex hydrogeology of karst aquifers, the coupled measurementof cave drip rate and spring discharge monitoring has been analyses for the intense rainfall event recorded in the Supramonte karst massif (Central East Sardinia, Italy) on 18 November 2013. During this extreme episode, more than450 mm of precipitati on fell in this area in just 12 hours, reaching a rainfall intensity of 60 mm/hour and triggering afl ash fl ood with catastrophic consequences. For the monitoring of such episode, drip rate monitoring was performed at the Perdeballa cave located at theboundary of the carbonate aquifer in the upstream part of the Supramonte catchment area, while groundwater discharge was measured at Su Gologone spring, the main karst resurgence located 21 kilometres downstream from the cave. During this extreme event, cave drip rate increases from the base level of 30 mL/hour up to 480 mm/hour. At the karstspring, the peak discharge reached around 40 cubic metres per second, a value of two orders of magnitude greaterthan the average fl ow of the spring (around 200 L/s). The lag among peak rainfall intensity, the highest cave drip rate and spring water level indicates the response ti me ofthe karst system to this more and more extreme events.