Giancarlo Dalla Fontana

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

Abstract Road 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. To simulate the absence of alteration, the surface was smoothed considering moving windows of varying size. In the analysis, we used a 1 and 0.5 m Airborne Laser Swath Mapping technology (ALSM), using LiDAR (Light Detection And Ranging), and 0.2 m Terrestrial Laser Scanner (TLS) derived Digital Terrain Models (DTMs). The aim of the work is to underline the effectiveness of the proposed method based on high resolution topography in the detailed recognition of surface flow direction alteration due to roads, but also trail networks. We propose an automatic method to map at a large scale such alterations, also in areas where it is difficult to recognize them without a trail network surveyed in the field. This methodology could be considered as a support for modeling (i.e., terrain stability and erosion models), and it can be used to interactively assist the design of new infrastructure to reduce their effects on surface instabilities. The reported methodology could also have a role in risk management and environmental planning for mountain areas where tourism and the related economic activities are critical, and where also trails deserve attention due to induced slope instabilities.

Current Behaviour and Dynamics of the Lowermost Italian Glacier (Montasio Occidentale, Julian Alps)

Abstract Smaller glaciers (<0.5 km2) react quickly to environmental changes and typically show a large scatter in their individual response. Accounting for these ice bodies is essential for assessing regional glacier change, given their high number and contribution to the total loss of glacier area in mountain regions. However, studying small glaciers using traditional techniques may be difficult or not feasible, and assessing their current activity and dynamics may be problematic. In this paper, we present an integrated approach for characterizing the current behaviour of a small, avalanche‐fed glacier at low altitude in the talian lps, combining geomorphological, geophysical and high‐resolution geodetic surveying with a terrestrial laser scanner. The glacier is still active and shows a detectable mass transfer from the accumulation area to the lower ablation area, which is covered by a thick debris mantle. The glacier owes its existence to the local topo‐climatic conditions, ensured by high rock walls which enhance accumulation by delivering avalanche snow and reduce ablation by providing topographic shading and regulating the debris budget of the glacier catchment. In the last several years the glacier has displayed peculiar behaviour compared with most glaciers of the uropean lps, being close to equilibrium conditions in spite of warm ablation seasons. Proportionally small relative changes have also occurred since the Little Ice Age maximum. Compared with the majority of other Alpine glaciers, we infer for this glacier a lower sensitivity to air temperature and a higher sensitivity to precipitation, associated with important feedback from increasing debris cover during unfavourable periods.

Reconstructing Fluctuations of La Mare Glacier (Eastern Italian Alps) in the Late Holocene: New Evidence for a Little Ice Age Maximum Around 1600 AD

Abstract Field observations, old terrestrial photographs and maps, aerial orthophotos and detailed geomorphological mapping were used for compiling and validating a 119‐year cumulative record of terminus changes for a are lacier, astern talian lps. ate olocene glacier maxima preceding direct observations were reconstructed by applying age dating techniques (radiocarbon and lichenometry) to glacial deposits in the proglacial area of the glacier. Results show that the glacier reached its maximal position around 1600 ad, followed by smaller advances in the eighteenth century, while in the nineteenth century it did not reach or overrun these positions. A similar behaviour for neighbouring glaciers was reported by previous works, documenting absolute ate olocene maxima in the seventeenth or eighteenth centuries. By contrast, multi‐century reconstructions available for the north‐western lps show that in the nineteenth century, glaciers were at their maximum or very close to previous maxima achieved in the first half of the seventeenth century. Climatic causes for these discrepancies have been examined, analyzing multi‐proxy climatic reconstructions starting in 1500 ad, but also morphodynamic processes linked to the bedrock characteristics of a are lacier could have played a role in modulating its response to climatic changes.

Enhanced estimation of glacier mass balance in unsampled areas by means of topographic data

Abstract A new method was developed to estimate the mass balance in unsampled areas from existing datasets. Three years of mass-balance data from two glaciers in the central Italian Alps were used to develop and test a multiple-regression method based exclusively on a 10m resolution digital terrain model. The introduction of a relative elevation attribute, which expresses the degree of wind exposure of the gridcells, notably increased the amount of explainable variance in winter balance with respect to altitude itself. The summer balance is highly correlated with elevation, but, in order to obtain reliable extrapolations, the clear-sky shortwave radiation and the diurnal cloud-cover cycle had to be taken into account. The net annual mass balance on a glacier system comprising the two monitored glaciers was calculated by applying both a single regression of winter and summer balance with altitude and the new regression method. The consistency of results was assessed against measured net balances and snow-cover maps drawn in the ablation season. The results of the new method were in close agreement with observations and proved to be less sensitive to the spatial representation of the sampled areas.

DISCOVERY OF COLD ICE IN A NEW DRILLING SITE IN THE EASTERN EUROPEAN ALPS

During autumn 2011 we extracted the first ice cores drilled to bedrock in the eastern European Alps from a new drilling site on the glacier Alto dell’Ortles (3859 m, South Tyrol, Italy). Direct ice core observations and englacial temperature measurements provide evidence of the concomitant presence of shallow temperate firn and deep cold ice layers (ice below the pressure melting point). To the best of our knowledge, this is the first cold ice observed within a glacier of the eastern European Alps. These ice layers probably represent a unique remnant from the colder climate occurring before ~1980 AD. We conclude that the glacier Alto dell’Ortles is now changing from a cold to a temperate state. The occurrence of cold ice layers in this glacier enhances the probability that a climatic and environmental record is fully preserved in the recovered ice cores.

Rocky Headwaters in the Dolomites, Italy: Field Observations and Topographic Analysis

Rock outcrops cover large areas of alpine headwaters and are entrenched by chutes and couloirs, which are controlled by faults in bedrock. These widespread landforms play an important role in delivering sediment to lower basin slopes. High-resolution topographical data from LiDAR surveys allow investigation of morphometric characteristics and sediment transport processes in these features. Using aerial photo interpretation, field surveys, and topographic analyses of LiDAR data, this paper quantifies the morphological characteristics of rocky couloirs and their drainage basins, and the relationship between these features and the structural setting, in a study area in the Dolomites (northeastern Italy). Rock basins are characterized by small sizes (surface area < 0.066 km2) and high average basin slopes (up to 2.1 m m−1). The analysis of contributing area and local slope outlines the difference between these rock basins, and even smaller and steeper rock faces entrenched by very shallow chutes, which were defined as interbasin areas. We consider rocky couloirs and rock basins in the headwaters of the Dolomites to be part of the channel network, since channeled flow occurs in the couloirs during storms. High-intensity rainstorms trigger debris flows as evidenced from local scouring, especially in the lower parts of the couloirs. The longitudinal profiles of the couloirs are overall linear, but the high-resolution data display distinct high-slope and low-slope stretches forming steps, that may function as localized sources and sinks for debris flows. The cross-sectional widths of the couloirs do not appear related to upslope area; this may be due to both structural control on cross-sectional geometry and complex erosion of the couloir by debris flows.

Multi-temporal analysis of sediment source areas and sediment connectivity in the Rio Cordon catchment (Dolomites)

In this study, two sediment source inventories produced in 1994 and 2006 have been compared and an analysis of sediment connectivity has been carried out in a 5 km2 headwater catchment (Rio Cordon catchment, Eastern Italian Alps). The 2006 sediment sources inventory was produced through an integrated approach encompassing field survey and interpretation of geomorphometric parameters (i.e., openness, surface roughness and wetness index) computed on a LiDAR-derived 1-m resolution DTM. The 2006 inventory aimed at updating a sediment source dataset dating back to 1994, which had been implemented by means of traditional techniques, i.e., field survey and interpretation of aerial photographs. Moreover, a topography-based index of connectivity (Cavalli et al., 2013) has been applied in order to evaluate the potential connection of 2006 sediment source areas with regard to the channel network. The analysis indicates that using a geomorphometric approach based on high-resolution LiDAR DTM in combination with field survey helps obtaining reliable and detailed sediment sources inventory and improving sediment delivery assessment.