Olga Petrucci

Adaptation to flood risk - results of international paired flood event studies

As flood impacts are increasing in large parts of the world, understanding the primary drivers of changes in risk is essential for effective adaptation. To gain more knowledge on the basis of empirical case studies, we analyze eight paired floods, that is, consecutive flood events that occurred in the same region, with the second flood causing significantly lower damage. These success stories of risk reduction were selected across different socioeconomic and hydro-climatic contexts. The potential of societies to adapt is uncovered by describing triggered societal changes, as well as formal measures and spontaneous processes that reduced flood risk. This novel approach has the potential to build the basis for an international data collection and analysis effort to better understand and attribute changes in risk due to hydrological extremes in the framework of the IAHSs Panta Rhei initiative. Across all case studies, we find that lower damage caused by the second event was mainly due to significant reductions in vulnerability, for example, via raised risk awareness, preparedness, and improvements of organizational emergency management. Thus, vulnerability reduction plays an essential role for successful adaptation. Our work shows that there is a high potential to adapt, but there remains the challenge to stimulate measures that reduce vulnerability and risk in periods in which extreme events do not occur.

Occurrence of landslide events and the role of climate in the twentieth century in Calabria, southern Italy

Abstract A methodological approach based on analysing landslides that occurred over a long period and climatic data characterizing that period is presented. The method investigates whether there are any effects of climate on landslide triggering. The approach has been tested in Calabria (Italy). Both landslide and climatic data have been obtained from available databases that have been expanded. Landslide data came from historical archives and newspapers, whereas the climatic analysis is based on daily and monthly series of rainfall and temperature. The method simplifies the comparative analysis of several time series by defining some indices (the monthly, bi-monthly … m-monthly indices of precipitation, temperature, wet days and precipitation, and the monthly landslide number) that can be used to study phenomena, such as landslides, that are characterized by spatial and temporal variability. For Calabria, the number of landslides is correlated to monthly precipitation, wet days and precipitation intensity. Thus, landslide occurrence could be roughly forecast using these climatic data. Despite the favourable climatic trend, landslides are not decreasing because the recent utilization of landslide-prone areas increases the vulnerability.

Slope movements induced by rainfalls damaging an urban area: the Catanzaro case study (Calabria, southern Italy)

Calabria is one of the Italian regions mostly affected by mass movements. The case study of a densely populated neighborhood (Ianò) located in the central-western sector of Calabria is presented. The several landslides triggered in February 2010 caused heavy damages to the built area, infrastructures and productions of this neighborhood, and increased the risk for the inhabitants. The results obtained through field surveys, photo interpretation, analyses of rainfall data and of the urban fabric evolution, historical survey on the reports of the damages caused by landslides, have enabled to formulate hypotheses on the potential causes that triggered landslide events and produced severe consequences on the area. These results have revealed that almost all landslides of February 2010 are partial reactivations of pre-existing landslide deposits. Moreover, the analyses have indicated a critical role of cumulative rainfalls over an interval of 15 days. However, the severe damage framework is explained through an unplanned urbanization which took place across the years on an area characterized by a high level of instability per se. Some buildings have been erected in proximity of or within pre-existing landslide scarps; in other cases, buildings have been constructed even inside the landslide bodies.

Gender, age and circumstances analysis of flood and landslide fatalities in Italy

Floods and landslides are frequent and destructive geo-hydrological hazards that cause harm to people every year. We analysed data on 1292 landslide and 771 flood fatalities that occurred in Italy in the 50-year period 1965-2014, to determine the dependence of the fatalities on gender and age and the circumstances of death by type of hazard. The multinomial probability mass function of the expected fatalities by gender and age, as reported by national census data, were estimated and compared with the observed landslide and flood fatalities. We identified the age categories over or under represented when the observed fatalities were respectively higher or lower than the modelled expected deaths. We found that in Italy males are more vulnerable to floods and landslides for most of the age categories. Apart from children, males are over-represented up to the age of 89 for floods and up to 79 for landslides, whereas females are under-represented up to the age of 59 for floods and landslides, and over-represented above 70 for floods and between 60 and 79 for landslides. To consider the demographic and socio-cultural changes over time, we performed a temporal analysis splitting the record into two non-overlapping subsets of 25year each. The analysis demonstrated that the over-representation of males compared to the females, both for landslide and flood is statistically significant and does not vary in time, indicating a different propensity towards the risk taking and a different degree of exposure between males and females. Analysis of the data allowed to identify the common circumstances of death. Landslides fatalities occurred frequently indoor, whereas the majority of the flood fatalities occurred outdoor, outlining the different dynamics of the hazards. Floods killed numerous people along roads and drivers or passengers travelling in vehicles. We expect that the results of this work will be helpful to design recommendations for self-protecting actions, and proactive policies that can contribute to reduce the human toll of floods and landslides in Italy, and elsewhere.

Assessing future changes in the occurrence of rainfall-induced landslides at a regional scale

According to the fifth report of the Intergovernmental Panel on Climate Change, an increase in the frequency and the intensity of extreme rainfall is expected in the Mediterranean area. Among different impacts, this increase might result in a variation in the frequency and the spatial distribution of rainfall-induced landslides, and in an increase in the size of the population exposed to landslide risk. We propose a method for the regional-scale evaluation of future variations in the occurrence of rainfall-induced landslides, in response to changes in rainfall regimes. We exploit information on the occurrence of 603 rainfall-induced landslides in Calabria, southern Italy, in the period 1981-2010, and daily rainfall data recorded in the same period in the region. Furthermore, we use high-resolution climate projections based on RCP4.5 and RCP8.5 scenarios. In particular, we consider the mean variations between a 30-year future period (2036-2065) and the reference period 1981-2010 in three variables assumed as proxy for landslide activity: annual rainfall, seasonal cumulated rainfall, and annual maxima of daily rainfall. Based on reliable correlations between landslide occurrence and weather variables estimated in the reference period, we assess future variations in rainfall-induced landslide occurrence for all the municipalities of Calabria. A +45.7% and +21.2% average regional variation in rainfall-induced landslide occurrence is expected in the region for the period 2036-2065, under the RCP4.5 and RCP8.5 scenario, respectively. We also investigate the future variations in the impact of rainfall-induced landslides on the population of Calabria. We find a +80.2% and +54.5% increase in the impact on the population for the period 2036-2065, under the RCP4.5 and RCP8.5 scenario, respectively. The proposed method is quantitative and reproducible, thus it can be applied in similar regions, where adequate landslide and rainfall information is available.

Impacts of past and future land changes on landslides in southern Italy

Land use and land cover (LULC), as well as their geographical and temporal variations, affect landslide occurrence and the related risk, in ways that are difficult to determine. Here, we propose a method for the regional analysis of variations in landslide frequency and distribution in response to observed and projected LULC changes. The method is quantitative and reproducible. We test it in Calabria, southern Italy, where a catalogue of 7037 landslides occurred between 1921 and 2010 is available. First, we defined empirical relationships linking the observed LULC variations to landslide occurrence. We found that, in the period 1921–1965, the majority of the landslides occurred in forests and grassland areas, while, in the period 1966–2010, the landslide density became higher in grassland areas, lower in arable lands and remained about constant in the forests. We consider this an evidence of the positive effect of agricultural practices and land management in reducing landslide occurrence. We noticed that both the landslide occurrence and the distribution of the vulnerable elements changed in the observation period. Then, we calculated the projected variations (to 2050) in landslide occurrence related to 32 scenarios of LULC changes. Our projections reveal a modest increase in landslide occurrence in all scenarios, in the range from 0.9 to 3.2%, with an average increase of 2%. Considering all scenarios, we expect an increase in the number of landslides due to LULC variations in 291 municipalities in Calabria (71%), with 4 municipalities where the increase is expected to exceed 50%. We maintain that the observed and the projected variations in the occurrence of landslides in Calabria are related to changes in natural (i.e. the number and distribution of the triggering events) and environmental and societal (i.e. the number and the distribution of the exposed elements) components.

Historical Climatology of Storm Events in the Mediterranean: A Case Study of Damaging Hydrological Events in Calabria, Southern Italy

In this chapter, based on the data available in a regional database, some severe damaging hydrogeological events (DHEs) occurred in the last century in Calabria (Italy) have been described in terms of both triggering rain and damaging effects. Among the analyzed cases, there are only three long standing events (1951, 1953 and 1972), while the others are shorter. As far as the triggering rain, the 1951 and 1953 events are still not surpassed, and fortunately it is the same for the number of victims. If we consider the event occurred on 2000 as an exception caused by the negligence of the municipality that allowed a campsite so close to the river, the number of victims per event shows a decreasing trend. This can be a normal evolution which occurs in developed countries, where, because of an improving event management, damage to people tend do decrease and damage to goods to increase. The seasonality is clear: the majority of the events occurred between September and November, which in Calabria are the rainiest months. In terms of damaging phenomena, landslides were always the most frequent type. Greatest damage, especially in terms of victims, was caused by floods, the effects of which were often amplified by sea storms. The interrelations between the different phenomena, as the relationship between floods and landslides carrying debris into the river network and the connection between floods and sea storms, confirm that DHEs have to be studied with a general approach and taking into consideration all the phenomena and their interrelation which can amplify damage and cause cascading effects.

Hydrogeological monitoring and image analysis of a mudslide in Southern Italy

Abstract This paper describes a methodological example of a data-integration procedure to improve the knowledge of landslide hazard related to a seismic area in the southern Apennine (Italy). Attention is focused on remote sensing data. The analysis is validated using detailed topographical, geophysical, geotechnical and hydrogeological data as ground truth. The investigated phenomenon, which started at the end of 1993, is an earthflow. The presented methodology recommends the combined use of DEM, multi-temporal panchromatic visible aerial photographs and thermal infrared images. The integration between these data and multidisciplinary monitoring data proved useful. The main hydrogeological pattern, the geological and geomorphological framework and the areas of latent instability can be clearly determined. Insight can be gained through the synoptic slope view in the relative short time needed to carry out the analysis. The proposed approach can be regarded as a useful contribution to the evaluation of landslide hazard, particularly during emergency periods.

Rainfall-Related Phenomena Along a Road Sector in Calabria (Southern Italy)

This paper proposes an approach for the relative assessment of damage caused along roads by landslides and floods, which are known as Rainfall-Related Phenomena (RRP). The proposed approach aims to obtain (a) the trend of phenomena occurrences through the analysed period, classified in terms of both the type of triggering phenomenon and relative damage; (b) the location of damage data, allowing the creation of a map of critical points that must either be monitored during rainfall periods or urgently need defensive work; and (c) a sketch of the primary circumstances that lead to human injuries along the analysed road. Finally, an application for a road track in Calabria (Southern Italy) is presented.

Carbonate Coastal Aquifer of Vlora Bay and Groundwater Submarine Discharge (Southwestern Albania)

Abstract The study discusses the large karstic coastal aquifer of Vlora Bay. This case is peculiar, as the submarine groundwater discharge has a relevant rate of terrestrial inflow in an almost closed bay that is located in an environmentally valuable area. The study is based on four methodological activities: geological and hydrogeological conceptualisation, climatic study and hydrological balance, numerical modelling, and monitoring. A geodatabase was created considering hundreds of data points (wells, springs, rivers, lagoons, and seas) and monthly time series of rainfall, temperature, and river discharge. Monitoring activity was realised over a hydrological year, installing a rainfall network tool and using a network of tens of sampling points, including springs, wells, lagoons, and sea. Chemical–physical and stable isotope determinations were realised. Two main groups of aerial springs are fed by the aquifer, one of which is of a coastal type. The total spring discharge is roughly 4 m3/s. The submarine groundwater discharge (SGD) was assessed as being equal to 1.4 m3/s on the basis of the current rate of anthropic discharge and climatic conditions. The study showed the peculiarities of this carbonate coastal aquifer and the importance of its groundwater, which is the chief water source for the third-largest Albanian town.The groundwater quality was generally high, mainly due to the negligible presence of contamination sources on the relief in which the aquifer outcrops. The rate of seawater intrusion effects was also low, thanks to favourable aquifer three-dimensional geometry and high recharge levels. The increasing anthropic activities constitute a relevant risk in the absence of the introduction of rigorous land and water management criteria.