distributed mass balance modelling on two neighbouring glaciers in ortles cevedale italy from 2004 to 2009

AbstractA 6 year application of an enhanced temperature-index mass-balance model to Careser and La Mare glaciers, Eastern Italian Alps, is presented. The two glaciers exhibit very different characteristics, and a comprehensive dataset of distributed mass-balance measurements was used to test the model performance. The model was run using meteorological data acquired outside the glaciers. The work was focused on two main aspects: (1) the development of a morphological redistribution procedure for snow, and (2) the comparison of three different melt algorithms proposed in the literature. The results show that the simple method proposed for snow redistribution can greatly improve simulation of winter balance, and further improvements would be achievable by collecting data on inaccessible and high-altitude areas. All three melt formulations displayed a good skill level and very similar results in modelling the mass-balance distribution over glacier areas, with slightly better results from a multiplicative algorithm in capturing the vertical balance gradient. The simulation errors are related to aspect and elevation, and tend to be spatially aggregated. Some assumptions concerning the spatial and temporal distribution of air temperature and incoming solar radiation, although reasonable and widely used in the literature, may be responsible for this aggregation. Hence, there is a need to further investigate the processes that regulate the distribution of melt energy, and that appear to control the current deglaciation phase in this area

Impiego di DTM ad alta risoluzione per la misura automatica di larghezze al bankfull

The study of the morphological characteristics of rivers and of their degree morphological alterations, is a basis for a proper management of mountain watershed: the availability of detailed topographic data is a key tool. The evaluation of channel geometry variability, determined by hydrodynamic and geomorphological processes, is usually gathered through field surveys, or through visual interpretations of digital orthophotos. However, the topographic data obtained through visual interpretation are not sufficiently accurate to allow the identification and the correct mapping of channel geometries. On the other hand, even if they provide more reliable data, field surveys require considerable time and financial resources, and they are often challenged by the inaccessibility of the areas under analysis. It is therefore strategic to adopt new and more accurate methods to estimate channel geometries, based on the availability of high-resolution data, such as the one derived from airborne laser scanner (LiDAR). LiDAR technology enables the acquisition of high resolution topographic data over large areas, with vertical and horizontal accuracy of a few centimeters (10-20 cm for the vertical component and 0.5-2 m for horizontal), contributing to a better representation the Earth's surface at more affordable costs. In mountain areas many studies have explored the potential of LiDAR DTM for the proper characterization of the network and the objective of this paper is to highlight their potential in the automatic determination of values representative of bankfull widths. The analysis is based on a topographic index (Elevation Percentile) used to measure the variability of the elevation from 1 m DTM resolution. This index is derived by calculating within a moving window the number of cells with elevation higher than the central pixel. This number is then normalized to the extension of the moving window: channelized areas have an EP value greater than convex areas. Applying a statistical threshold to the EP, it is possible to obtain a Boolean map of potential river bed. The geometries derived from this map are approximated due to the resolution of the DTM, but it is possible to consider the topographic representation of the banks and to approximate the bankfull width. In an automatic manner, moving downstream along the thalweg, it is possible to estimate perpendicularly to the flow directions, the bankfull width at each point of the network, with the above-mentioned limit of the DTM resolution. Automatically derived widths show a good agreement with those detected in the field, with low values of RMSE, and the range of the estimated values is compatible with the surveyed ones

Downstream hydraulic geometry relationships: Gathering reference reach-scale width values from LiDAR

This paper examines the ability of LiDAR topography to provide reach-scale width values for the analysis of downstream hydraulic geometry relationships along some streams in the Dolomites (northern Italy). Multiple reach-scale dimensions can provide representative geometries and statistics characterising the longitudinal variability in the channel, improving the understanding of geomorphic processes across networks. Starting from the minimum curvature derived from a LiDAR DTM, the proposed algorithm uses a statistical approach for the identification of the scale of analysis, and for the automatic characterisation of reach-scale bankfull widths. The downstream adjustment in channel morphology is then related to flow parameters (drainage area and stream power). With the correct planning of a LiDAR survey, uncertainties in the procedure are principally due to the resolution of the DTM. The outputs are in general comparable in quality to field survey measurements, and the procedure allows the quick comparison among different watersheds. The proposed automatic approach could improve knowledge about river systems with highly variable widths, and about systems in areas covered by vegetation or inaccessible to field surveys. With proven effectiveness, this research could offer an interesting starting point for the analysis of differences betweenwatersheds, and to improve knowledge about downstream channel adjustment in relation, for example, to scale and landscape forcing (e.g. sediment transport, tectonics, lithology, climate, geomorphology, and anthropic pressure)

recognition of surface flow processes influenced by roads and trails in mountain areas using high resolution topography

AbstractRoad networks in mountainous forest landscapes have the potential to increase the susceptibility to erosion and shallow landsliding. The same issue is observed also for minor trail networks, with evidences of surface erosion due to surface flow redistribution. This could be a problem in regions such as the Italian Alps where forestry and tourist activities are a relevant part of the local economy. This is just one among the several effects of modern anthropogenic forcing: it is now well accepted by the scientific community that we are living in a new era where human activities may leave a significant signature on the Earth, by altering its morphology, and significantly affecting the related surface processes. In this work, we proposed a methodology for the automatic recognition of roads and trails induced flow direction changes. The algorithm is based on the calculation of the drainage area variation in the presence, or in the absence of anthropic features such as roads and trails on hillslopes. T..

Air temperature variability over three glaciers in the Ortles-Cevedale (Italian Alps): Effects of glacier fragmentation, comparison of calculation methods, and impacts on mass balance modeling

Glacier mass balance models rely on accurate spatial calculation of input data, in particular air temperature. Lower temperatures (the so-called glacier cooling effect), and lower temperature variability (the so-called glacier damping effect) generally occur over glaciers, compared to ambient conditions. These effects, which depend on the geometric characteristics of glaciers and display a high spatial and temporal variability, have been mostly investigated on medium- to large-size glaciers so far, while observations on smaller ice bodies are scarce. Using a dataset from 8 on-glacier and 4 off-glacier weather stations, collected in summer 2010 and 2011, we analyzed the air temperature distribution variability and wind regime over three different glaciers in the Ortles-Cevedale. The magnitude of the cooling effect and the occurrence of katabatic boundary layer (KBL) processes showed remarkable differences among the three ice bodies, highlighting suggesting the likely existence of important reinforcing mechanisms during glacier decay and disintegration. None of the methods proposed in the literature for calculating on-glacier temperature from off-glacier data fully reproduced our observations. Among them, the more physically-based procedure of Greuell and B\uf6hm [1998] provided the best overall results where the KBL prevail, but it was not effective elsewhere (i.e. on smaller ice bodies and close to the glacier margins). The accuracy of air temperature estimations strongly impacted the results from a mass balance model which was applied to the three investigated glaciers. Most importantly, even small temperature deviations caused distortions in parameter calibration, thus compromising the model generalizability

Il servizio WCTS del Geoportale Nazionale

The 2007/2/CE INSPIRE directive requires every Member State to implement a set of services to facilitate the interchange of spatial data; the Coordinate Transformation Service (CTS) is one of the geometric transformation services required by the directive. The Italian National Geoportal (GN) has recently published a new set of public access services that enable the users to transform and convert the coordinate reference system of geographic data within the Italian territory using the high-accuracy correction data provided by the Istituto Geografico Militare Italiano (IGM). This article will illustrate these newly published services: a browser-based web application to transform raster and vector files or sets of coordinates and an OGC-compliant Web Coordinate Transformation Service (WCTS) that performs on the fly transformation of GML (Geography Markup Language) data

High-Resolution monitoring of current rapid transformations on glacial and periglacial environments

Glacial and periglacial environments are highly sensitive to climatic changes. Processes of cryosphere degradation may strongly impact human activities and infrastructures, and need to be monitored for improved understanding and for mitigation/adaptation. Studying glacial and periglacial environments using traditional techniques may be difficult or not feasible, but new remote sensing techniques like terrestrial and aerial laser scanner opened new possibilities for cryospheric studies. This work presents an application of the terrestrial laser scanner (TLS) for monitoring the current rapid changes occurring on the Montasio Occidentale glacier (Eastern Italian alps), which is representative of low-altitude, avalanche-fed and debris-cover glaciers. These glaciers are quite common in the Alps but their reaction to climate changes is still poorly known. The mass balance, surface velocity fields, debris cover dynamics and effects of meteorological extremes were investigated by repeat high-resolution TLS scanning from September 2010 to October 2012. The results were encouraging and shed light on the peculiar response of this glacier to climatic changes, on its current dynamics and on the feedback played by the debris cover, which is critical for its preservation. The rapid transformations in act, combined with the unstable ice mass, large amount of loose debris and channeled runoff during intense rainfalls, constitute a potential area for the formation of large debris flows, as shown by field evidences and documented by the recent literature

The current deglaciation of the Ortles-Cevedale massif (Eastern Italian Alps): impacts, controls and degree of imbalance.

The Ortles-Cevedale is the largest glacierized mountain group of the Italian Alps hosting 112 ice bodies, with a total area of 76.8 km2. Since the 1980\u2019s, this massif is undergoing a rapid deglaciation, as most of the mountain ranges in the European Alps. The aims of this work were: i) to quantify area and volume change of the Ortles- Cevedale glacier system from the 1980s to the 2000s; ii) to improve the knowledge of factors controlling the spatial variability of the deglaciation; and iii) to assess the degree of imbalance of individual glaciers with respect to the present climate conditions. Two inventories were created, based on Landsat5 TM scenes of 20-09-1987 and 31-08-2009. Contrast-enhanced composites (bands TM5, TM4 and TM3), aerial photos and field surveys (for the most recent period) were used to correct the automatic delineation of glaciers derived from a hard classification based on a threshold applied to a TM3/TM5 ratio image. Since Landsat scenes were acquired at the end of the ablation seasons and fresh snow was absent, the accumulation areas could be roughly determined by mapping the snow covered area. This region was identified from the difference in reflectance between snow and ice in the near infrared band of Landsat (TM4), and mapped after correcting topographic effects to determine surface reflectance. The area-averaged geodetic mass budget was then calculated for the individual glaciers by differencing two Digital Terrain Models (2000s minus 1980s, derived from LiDAR and aerial photogrammetry) and combining the result with the glacier outlines. Afterwards, we examined the mass balance data using statistical analyses (Correlation matrices, Principal Component Analysis, Cluster Analysis). This allowed us highlighting clusters of glaciers, which exhibit a similar behavior, identify the outlayers and the relative influence of the factors controlling spatial variability of the mass losses. Finally, we assessed the degree of imbalance of individual glaciers by comparing the current Accumulation Area Ratios (AAR) with the balanced-budget AAR (AAR0), the latter also accounting for the debris cover of glaciers. We found that the total area loss of the Ortles-Cevedale glaciers from 1987 to 2009 amounts to 23.5 km2, i.e. 23.4% of the initial area. On the other hand, the AAR of the entire glacier system was 0.3 in both investigated years. The overall debris cover increased from 10.5% to 16.3%. The geodetic mass balance rate was -0.7 m w.e. y1(as an average on 112 ice bodies), ranging from -0.1 to -1.7 m w.e. y1. We also found that the main controls of the differing change of single glaciers are related to their hypsometry (elevation range and slope), AAR, feeding source and debris cover. Interestingly, a significant correlation was found between AAR, AAR0 and debris cover. This information was used to assess and visualize the needed additional reduction of individual glaciers to reach equilibrium with the current size of their accumulation areas. This amounts on average to a further reduction of 40% of the current areal extent of glaciers

A model-based early warning system for runoff-generated debris-flow occurrence: Preliminary results

Early warning systems for debris flows are low cost measures for mitigating this kind of hazard. The early warning systems provide a timely alert for upcoming events in order to take protective measures, such as closing railways-roads, evacuating people from the threatened areas, and put rescue forces into readiness. These systems usually are sensor-based, and the alert time is the interval between the timing of the first detachment of debris flow by a sensor and its arrival into the threatened area. At the purpose of increasing the alert time, we propose an early warning system based on a model-cascade: nowcasting, hydrological- and triggering models. Nowcasting anticipates rainfall pattern that is transformed into runoff by the hydrological model. The triggering model estimates the volume of sediments that the runoff can entrain, and compares it with a critical threshold. If this is exceeded the alert is launched. The proposed early warning system is tested against the available data of the Rovina di Cancia (Northeast Italy) site