F. Luino

Application of a model to the evaluation of flood damage

This paper presents the initial results of a common methodology for the evaluation of damage produced by a flood. A model has been developed for flood damage estimation based on a geographic information system (GIS). It could be used by land administration bodies and insurance companies to manage flood-related damage data. The model simulates flood scenarios and evaluates expected economic losses from the impact of floodwaters on exposed elements, through the application of a computational model elaborated by GIS. During the development of the model, the Boesio Stream, a small watercourse flowing into Lake Maggiore (Lombardy, northern Italy) which was recently affected by a flash flood, was used as case study to test and calibrate the methodology. The method could be used either as a forecasting tool to define event scenarios, utilizing data from events simulated with a hydraulic model, or for real-time damage assessment after a disaster. The approach is suitable to large-area damage assessment and could be appropriate for land use planning, civil protection and risk mitigation.

Catalogue of Rainfall Events with Shallow Landslides and New Rainfall Thresholds in Italy

In Italy, rainfall-induced shallow landslides are frequent and harmful phenomena. The prediction of their occurrence is of social significance for civil protection purposes. For the operational prediction of rainfall-induced shallow landslides empirical rainfall thresholds based on the statistical analysis of past rainfall conditions that triggered slope failures are commonly used. The paper describes a catalogue of 1981 rainfall events, which caused 2408 shallow landslides in Italy in the period 1996–2012. Information on rainfall-induced landslides was collected searching chiefly online newspaper archives, blogs, and fire brigade reports. For each documented failure, we reconstructed the triggering rainfall conditions (rainfall duration D and cumulated rainfall E) using national and regional rain gauge networks. We analysed the rainfall conditions to determine new ED rainfall thresholds for Italy. The calculated thresholds can be implemented in a landslide forecasting system to mitigate landslide hazard and risk.

Yet another disaster flood of the Bisagno stream in Genoa (Liguria, Italy): October the 9th -10th 2014 event

On 2014, 9th October, short and heavy rainfall hit the Bisagno Valley. The Bisagno stream overflowed again and flooded the center of Genoa, causing severe economic damage and a victim. This is the fourth serious flooding of the stream in the last fifty years, which shows similarities with the previous catastrophic ones in 1970, 1992 and 2011, both because of the trigger conditions, determined by the orography of the city of Genoa, and for the weather situations marked by an anticyclonic block converging over the Liguria Gulf.Between 06:00 a.m. on October the 9th and 12:00 a.m. on October the 10th in the Bisagno catchment were recorded some peaks of rain up to almost 140 mm/h and heaps of more than 550 mm/24hrs, which resulted in a rapid increase in the level of all streams of the Bisagno basin and subsequent flooding in the final stretch of the Bisagno stream, where the watercourse underflows covered by a long manhole for the last 1.4 kilometres.Interventions for risk mitigation through more careful weather-hydrology monitoring in nowcasting, the improvement of the civil protection activities, structural works on the watercourse, maintenance of the territory of the Bisagno catchment, a correct information and a timely communication to the population living in high risk areas are all urgently needed.

Rainfall Thresholds for Possible Occurrence of Shallow Landslides and Debris Flows in Italy

In mountain regions worldwide, rainfall-induced landslides and associated debris flows erode slopes, scour channels, and contribute to the formation of alluvial fans that may harm humans and destroy buildings. Rainfall-induced slope failures are frequent and widespread in Italy, where individual rainfall events can result in single or multiple slope failures in small areas or in very large regions. Most of the harmful failures were rainfall-induced, and several were shallow slides or debris flows. In the 60-year period 1950–2009, casualties due to landslides were at least 6,349, an average of 16 harmful events per annum. The large number of harmful events indicates the considerable risk posed by rainfall-induced shallow landslides and debris flows to the population of Italy (Guzzetti et al. 2005a; Salvati et al. 2010).

Flash Flood Events and Urban Development in Genoa (Italy): Lost in Translation

Coastal locations in the Mediterranean area experienced several geo-hydrological events from the beginning of the 3rd Millennium. Among the most flooded areas featuring the Ligurian coastal environment, Genoa is sorrowfully at international level, for the flash flood characteristics and consequent damage: the last event of 4 November 2011, once again, caused the loss of human lives. Genoa, in fact, can be considered an interesting case study for geo-hydrological risks: it can be said that to a general trend of increasing hazard, due to global and particular climate changes of the Mediterranean area, corresponds an increase of the vulnerability due to the urban growth on the flood plains. In this paper are analyzed the unusual meteorological characteristics of the Gulf of Genoa, the changes in the rate of daily precipitation using the recorded data at the station of Genoa, in use since 1833. The most significant periods of the land urban development are also briefly described. They have determined important changes of the territory, modifying the water balance of the basins in a considerable way.

Influence of geological, morphological and climatic factors in the initiation of shallow landslides in North Western Italy

Landslides are recurrent geomorphic processes in Italy and represent a serious economic and societal problem. Historical catalogues report thousands of landslide casualties since the 9th Century. The importance to predict landslide occurrence is particularly evident to prevent the effects of rapid mass movements. The mitigation of landslide-related risk needs the improvement of prediction skills, obtained with a better understanding of triggering mechanisms, which are peculiar of the specific geological and environmental settings. The prominent role of rainfall in mass movement activations is widely recognised in the scientific community and several authors all over the world have long attempted to define the critical values responsible for landslide initiation. In Italy, the National Department for Civil Protection (DPC) is funding a CNR-IRPI (National Research Council-Research Institute for Hydro-geological Protection) research, aiming at the definition of regional rainfall thresholds for shallow landslides for the entire national territory. In this study, we investigated the role of geological, morphological and climatic factors on the initiation of rainfall-induced slope failures in the Piedmont, the Aosta Valley and the Lombardy regions (NW Italy).

Rainfall events with shallow landslides in the Entella catchment (Liguria, Northern Italy)

In recent decades, the Entella River basin, in the Liguria Apennines, northern Italy, was hit by numerous intense rainfall events that triggered shallow landslides and earth flows, causing casualties and extensive damage. We analyzed landslide information obtained from different sources and rainfall data recorded in the period 2002–2016 by rain gauges scattered throughout the catchment, to identify the event rainfall duration, D (in h), and rainfall intensity, I (in mm h−1), that presumably caused the landslide events. Rainfall-induced landslides affected the whole catchment area, but were most frequent and abundant in the central part, where the three most severe events hit on 23–24 November 2002, 21–22 October 2013 and 10–11 November 2014. Examining the timing and location of the slope failures, we found that the rainfall-induced landslides occurred primarily at the same time or within 6 h from the maximum peak rainfall intensity, and at or near the geographical location where the rainfall intensity was largest. Failures involved mainly forested and natural surfaces, and secondarily cultivated and terraced slopes, with different levels of maintenance. Man-made structures frequently characterize the landslide source areas. Adopting a frequentist approach, we define the event rainfall intensity–event duration (ID) threshold for the possible initiation of shallow landslides and hyperconcentrated flows in the Entella River basin. The threshold is lower than most of the curves proposed in the literature for similar mountain catchments, local areas and single regions in Italy. The result suggests a high susceptibility to rainfallinduced shallow landslides of the Entella catchment due to its high-relief topography, geological and geomorphological settings, meteorological and rainfall conditions, and human interference. Analysis of the antecedent rainfall conditions for different periods, from 3 to 15 days, revealed that the antecedent rainfall did not play a significant role in the initiation of landslides in the Entella catchment. We expect that our findings will be useful in regional to local landslides early warning systems, and for land planning aimed at reducing landslide risk in the study area.

Revision of town planning in the Pioverna basin by the use of a multidisciplinary study to identify flood-prone areas: Valsassina, Lombardy Region, Northern Italy

This case study examines 10 municipal areas of the Pioverna River valley bottom (Valsassina, Northern Italy). Flood-prone areas were identified using historical research and geomorphological analysis. The historical research for different areas utilized records from the State technical office archives, Ministry of Public Works, Hydrographical Offices of the Po River, Civil Engineers, Records Office, public libraries, local and national newspapers archives, and municipal archives. Large amounts of historical data on past floods were collected, reviewed and validated on map flood-damaged locations. A geomorphological analysis was also conducted in which multi-temporal aerial photographs were studied and field surveys conducted to verify the reliability of the historical data and the planform changes of the Pioverna River course. The analysis of historical and geomorphological data produced a flood-prone area map with two different hazard zones identified along the Pioverna River. Aerophotogrammetric and cadastral maps were used to verify and update the urban planning of the 10 municipalities studied. The mosaic map of the urban planning shows four classes of land-use destinations, as defined according to the different levels of building exposure. On a matrix, the four land-use classes were matched to flood hazard sites of the two zones along the Pioverna River. The resulting map defines five classes of different flood risk. The results of the