Guido Nigrelli

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.

A method to reveal climatic variables triggering slope failures at high elevation

The air temperature in the Alps has increased at a rate more than twice the global average in the last century, and a significant increase in the number of slope failures has also been documented, in particular in glacial and periglacial areas. Thus, the relationship between climatological forcing and processes of instability at high elevation is worth analyzing. We provide a simple, statistically based method aimed at identifying a relationship between climate factors and the triggering of geohazards. Our main idea is to compare the meteorological conditions at the time when the instability occurred with the typical conditions in the same place. Carrying out a straightforward analysis based on the use of the empirical distribution function, we are able to determine whether any of the meteorological variables had nonstandard values in the lead-up to the slope failure event, and thus to identify the variables that are likely to have acted as triggering factors for the slope failure. The method has been tested on five events in the glacial and periglacial areas of the Piedmont Alps (Northwestern Italy) occurring between 1989 and 2008. Out of these five case studies, our research shows that four can be attributed to climatic anomalies (rise of temperature and/or heavy precipitation). The results of this study may contribute to developing knowledge about the relationships between climatic variables and slope failures at high elevations, providing interesting insights into the expected impact of ongoing global warming on geohazards.

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).

Climate variability and Alpine glaciers evolution in Northwestern Italy from the Little Ice Age to the 2010s

In this work, we analyze climate variability and glacier evolution for a study area in the Northwestern Italian Alps from the Little Ice Age (LIA) to the 2010s. In this area, glacier retreat has been almost continuous since the end of the LIA, and many glaciers are now extinct. We compared glaciological and climatic data in order to evaluate the sensitivity of glaciers to temperature and precipitation trends. We found that temperatures show significant warming trends, while precipitation shows no clear signal. After the 1980s, the total number of positive trends in temperature increased, particularly minimum temperature. The latter does not seem to be the only cause of glacier shrinkage but rather on acceleration of an ongoing trend documented since the end of the LIA. In some rare cases, the effects of warming trends on glacier dynamics have been accentuated by a concomitant decrease in precipitation. We hope that this study will contribute to increase the knowledge of the relationships between climate variation and glacier evolution in the Greater Alpine Region.

A web-based, relational database for studying glaciers in the Italian Alps

Glaciers are among the best terrestrial indicators of climate change and thus glacier inventories have attracted a growing, worldwide interest in recent years. In Italy, the first official glacier inventory was completed in 1925 and 774 glacial bodies were identified. As the amount of data continues to increase, and new techniques become available, there is a growing demand for computer tools that can efficiently manage the collected data. The Research Institute for Geo-hydrological Protection of the National Research Council, in cooperation with the Departments of Computer Science and Earth Sciences of the University of Turin, created a database that provides a modern tool for storing, processing and sharing glaciological data. The database was developed according to the need of storing heterogeneous information, which can be retrieved through a set of web search queries. The databases architecture is server-side, and was designed by means of an open source software. The website interface, simple and intuitive, was intended to meet the needs of a distributed public: through this interface, any type of glaciological data can be managed, specific queries can be performed, and the results can be exported in a standard format. The use of a relational database to store and organize a large variety of information about Italian glaciers collected over the last hundred years constitutes a significant step forward in ensuring the safety and accessibility of such data. Moreover, the same benefits also apply to the enhanced operability for handling information in the future, including new and emerging types of data formats, such as geographic and multimedia files. Future developments include the integration of cartographic data, such as base maps, satellite images and vector data. The relational database described in this paper will be the heart of a new geographic system that will merge data, data attributes and maps, leading to a complete description of Italian glacial environments.

High Elevation Rock Falls and Their Climatic Control: a Case Study in the Conca di Cervinia (NW Italian Alps)

One of the impacts of climate warming in recent years is the evident increase of the number of rock fall occurrences at high elevations. With few exceptions, these events have small magnitudes and thus are rarely reported and documented, even less so in the past. Therefore it is difficult to use a statistical approach to analyze of the relationships between climate warming and rock slope instability. On the other hand, it is often difficult to carry out a time analysis of meteorological conditions responsible for rock fall triggering, considering that very few automatic weather stations (AWS) are located in the areas and in the altitudinal range that are affected by cryosphere degradation (i.e. above c.a. 3,000 m elevation in the Alps), and that climatic conditions in high elevation environments are spatially and temporally variable. The present study addresses the above-mentioned issues through analysis of a series of small rock falls that occurred in the last 10 years on the Matterhorn and surrounding rock slopes. A specific focus is temperature: we present a preliminary analysis of the spatial and seasonal variability of the vertical temperature gradient in the Conca di Cervinia, where the Matterhorn is located, to illustrate the uncertainty in estimates of the thermometric conditions at high elevation rock fall sites.

A System for Assessing the Past, Present and Future of Glacial Resources

The cryosphere is especially sensitive to the fluctuations of climatic parameters, and specifically to ongoing global warming. Mountain glaciers, in particular, are good indicators of climatic trends, as they have response times to climate forcing which are intermediate between snow (which responds mainly to short-term climate forcing) and permafrost/ground ice, whose response is delayed in time and conditioned by a complex ensemble of factors. When studying glacier response to climate change, the main objectives are: (i) understand the terrestrial, local impacts of global climatic changes, (ii) develop scenarios of the future evolution of glaciated areas, according to the available global climatic projections. This two objectives have both scientific and applied merits. The latter are related to the importance of glaciers in the water cycle, in sediment fluxes, and as a source of natural hazards. The combination of historical and geomorphological information with numerical models of climate systems and glacier response to climate forcing is one of the most robust approaches to address the study of glacier evolution in response to climate fluctuations and change. In order to be promptly available for use, historical and geomorphological data (including climatic ones) need to be properly organized in information management systems, which guarantee the preservation and standardization of data, along with their easy processing and retrieval. The present contribution aims at illustrating the experience gained through the application of this multidisciplinary approach to glaciers of the western Italian Alps.

Relevance of Database for the Management of Historical Information on Climatic and Geomorphological Processes Interacting with High Mountain Landscapes

In the framework of the activities of the GeoClimAlp research group (Geomorphological impacts of Climate change in the Alps), a system of databases has been developed for the storage and management of glacial, periglacial and mountain digital resources, related to the Greater Alpine Region in general, and to the North-Western Italian Alps in particular. These resources are historical documents, publications, photos, aerial photographs, antique and recent maps, instrumental and survey data, related to: (i) alpine glaciers; (ii) natural instability processes and landforms in glacial/periglacial areas; (iii) hydro-climatic conditions of the alpine areas. This wealth of knowledge is mainly referred to the last 150 years. The GeoClimAlp digital resources stored in these databases are mainly used to: (i) study the spatial-temporal evolution of alpine glaciers; (ii) study the geomorphological processes, and in particular natural instability, that occur at high altitude (over 2000 m a.s.l.), in particular as a consequence of climate change; (iii) assess the hydro-climatic conditions of the glacial/periglacial and mountain areas; (iv) conduct research on climate change in the alpine environment.