Landslides, floods and sinkholes in a karst environment: the 1–6 September 2014 Gargano event, southern Italy

Abstract

Abstract. In karst environments, heavy rainfall is known to cause multiple geohydrological hazards, including inundations, flash floods, landslides and sinkholes. We studied a period of intense rainfall from 1 to 6 September 2014 in the Gargano Promontory, a karst area in Puglia, southern Italy. In the period, a sequence of torrential rainfall events caused severe damage and claimed two fatalities. The amount and accuracy of the geographical and temporal information varied for the different hazards. The temporal information was most accurate for the inundation caused by a major river, less accurate for flash floods caused by minor torrents and even less accurate for landslides. For sinkholes, only generic information on the period of occurrence of the failures was available. Our analysis revealed that in the promontory, rainfall-driven hazards occurred in response to extreme meteorological conditions and that the karst landscape responded to the torrential rainfall with a threshold behaviour. We exploited the rainfall and the landslide information to design the new ensemble–non-exceedance probability (E-NEP) algorithm for the quantitative evaluation of the possible occurrence of rainfall-induced landslides and of related geohydrological hazards. The ensemble of the metrics produced by the E-NEP algorithm provided better diagnostics than the single metrics often used for landslide forecasting, including rainfall duration, cumulated rainfall and rainfall intensity. We expect that the E-NEP algorithm will be useful for landslide early warning in karst areas and in other similar environments. We acknowledge that further tests are needed to evaluate the algorithm in different meteorological, geological and physiographical settings.

Economic Risk Evaluation in Urban Flooding and Instability-Prone Areas: The Case Study of San Giovanni Rotondo (Southern Italy)

“…In particular, from 1 to 6 September 2014, the study area was affected by a strong meteorological event that caused floods and heavy damage throughout the whole Gargano [19]. The most affected zones were those of recent development in the depressed areas of the basin.…”

Experimental assessment of the relationship between rainfall intensity and sinkholes caused by damaged sewer pipes

“…Both types of sinkholes have similar mechanisms, and the detailed process of occurrence is as follows (Brinkmann et al, 2008;Caramanna et al, 2008;Kuwano et al, 2010a;Martinotti et al, 2017;Oosthuizen and Richardson, 2011;Rogers, 1986): (1) A cavity is formed underground by external factors (the watersoluble ground layer dissolves in groundwater to cause a natural sinkhole, or soil erosion occurs along with the groundwater outflow due to sewage damage or excavation to cause an anthropogenic sinkhole). 2The groundwater level rises during rainfall and falls after the rainfall, causing the soil around the cavity to be lost and the cavity to expand.…”

“…Thus, there is a growing need to study the correlation between rainfall intensity and sinkhole occurrence. Martinotti et al (2017) showed that a period of torrential rain and the rainfall intensity triggered the natural sinkholes in Italy. Gao et al (2013) confirmed that the groundwater level rise due to extremely heavy rainfall has a significant effect on sinkhole generation in a karst environment in China.…”

A Vulnerable Environment Study in Karst Regions between 1991 and 2017: A Bibliometric Analysis

“…Currently, the understanding of the vulnerability of karst environment has reached a new height, which greatly facilitated the settlement of the degradation and pollution problems [5,[9][10][11][12][13][14].…”