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The Moscardo Torrent (eastern Italian Alps) is a small rugged catchment (drainage area 4.1 km2, range in elevation between 890 and 2043 m) frequently affected by debris flows that deliver large amounts of sediment to the receiving stream,... more
The Moscardo Torrent (eastern Italian Alps) is a small rugged catchment (drainage area 4.1 km2, range in elevation between 890 and 2043 m) frequently affected by debris flows that deliver large amounts of sediment to the receiving stream, and cause concerns for infrastructures located on the alluvial fan and near the confluence. Over the last decades, hydraulic control works were implemented in the main channel to limit bed erosion and to stabilize channel banks. Although the objectives of training works have been only partly achieved, check dams and hillslope stabilization works have affected the sediment transfer from hillslopes to the channels and along the main channel. The effects of hydraulic control works were investigated by means of multi-temporal Structure from Motion (SfM) surveys based on images taken from the ground and UAV. The ground and air based surveys were carried out over a channel reach in which two check dams have recently been built. SfM surveys were taken before and after three debris-flow events (occurred between June and July 2016), allowing the generation of four high-resolution Digital Elevation Models (DEMs). Geomorphic changes caused by the debris-flow events have been assessed in order to produce the DEM of Differences (DoDs with a 0.2 m spatial resolution) that allowed estimating erosion and deposition volumes in the study area. Furthermore a debris-flow monitoring system has been in operation in the Moscardo Torrent; the analysis of the videos and of the hydrographs recorded by ultrasonic sensors permitted to assess the debris-flow volumes. These estimates were used to characterize the magnitude of events in support of the topographic analysis. By examining the changing pattern of erosion and deposition over time it was possible to understand the check dams\u2019 effects on sediment dynamics. The results show that the new check dams effectively stored sediment transported by the three debris flows. However, once the check dams have been completely filled, they lost their functionality, letting sediment flow downstream along paths drawn accidentally by the torrent control works and by the morphology of debris-flow deposits. Moreover, debris-flow lobes deposited upstream of the check dams could act as sediment sources further increasing downstream debris-flow magnitude
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In mountain basins, long-term instrumental monitoring coupled with high-resolution topographic surveys can provide important information on sediment yield. The Gadria catchment, located in the eastern Italian Alps, typically features... more
In mountain basins, long-term instrumental monitoring coupled with high-resolution topographic surveys can provide important information on sediment yield. The Gadria catchment, located in the eastern Italian Alps, typically features several low-magnitude flood episodes and a few debris-flow events per year, from late spring to late summer. Beginning in 2011, sensors devoted to debris-flow detection (geophones, video cameras, flow stage sensors) were installed along the main channel, upstream of a retention basin. In case of debris flows, high-resolution topographical surveys of the retention basin are carried out multiple times per year. Rainfall is measured in the lower part of the catchment and at the headwaters, while passive integrated transponder tracing of bedload was performed in the main channel during spring and summer 2014. In this work, we present the reconstruction of the sediment dynamics at the catchment scale from 2011 to 2017. Results show that (i) coarse sediment y...
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Research Interests: Geology, Geomorphology, Soil Science, Remote Sensing, Photogrammetry, and 11 moreWorkflow, Environmental Chemistry, Earth and Environmental Sciences, Structure from Motion, Debris Flow, Biogeosciences, Pollution, Earth Surface Processes, Water Science and Technology, Structure from Motion (SFM), and digital elevation model (DEM)
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Digital elevation models (DEMs) built from repeated topographic surveys permit producing DEM of Difference (DoD) that enables assessment of elevation variations and estimation of volumetric changes through time. In the framework of... more
Digital elevation models (DEMs) built from repeated topographic surveys permit producing DEM of Difference (DoD) that enables assessment of elevation variations and estimation of volumetric changes through time. In the framework of sediment transport studies, DEM differencing enables quantitative and spatially-distributed representation of erosion and deposition within the analyzed time window, at both the channel reach and the catchment scale. In this study, two high-resolution Digital Terrain Models (DTMs) derived from airborne LiDAR data (2 m resolution) acquired in 2005 and 2011 were used to characterize the topographic variations caused by sediment erosion, transport and deposition in two adjacent mountain basins (Gadria and Strimm, Vinschgau-Venosta valley, Eastern Alps, Italy). These catchments were chosen for their contrasting morphology and because they feature different types and intensity of sediment transfer processes. A method based on fuzzy logic, which takes into account spatially variable DTMs uncertainty, was used to derive the DoD of the study area. Volumes of erosion and deposition calculated from the DoD were then compared with post-event field surveys to test the consistency of two independent estimates. Results show an overall agreement between the estimates, with differences due to the intrinsic approximations of the two approaches. The consistency of DoD with post-event estimates encourages the integration of these two methods, whose combined application may permit to overcome the intrinsic limitations of the two estimations. The comparison between 2005 and 2011 DTMs allowed to investigate the relationships between topographic changes and geomorphometric parameters expressing the role of topography on sediment erosion and deposition (i.e., slope and contributing area) and describing the morphology influenced by debris flows and fluvial processes (i.e., curvature). Erosion and deposition relations in the slope-area space display substantial differences between the Gadria and the Strimm basins. While in the former erosion and deposition clusters are reasonably well discriminated, in the latter, characterized by a complex stepped structure, we observe substantial overlapping. Erosion mostly occurred in areas that show persistency of concavity or transformation from convex and flat to concave surfaces, whereas deposi-tion prevailingly took place on convex morphologies. Less expected correspondences between curvature and to-pographic changes can be explained by the variable sediment transport processes, which are often characterized by alternation of erosion and deposition between different events and even during the same event.
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ABSTRACT Hydrate project Work package 4 report, December 2007
ABSTRACT Three storm events, occurred in 2006, 2007 and 2009 in the upper Adige River basin (Eastern Alps, northern Italy) have been analyzed. The first storm system (4 October 2006) generated a flash flood with almost no debris flows and... more
ABSTRACT Three storm events, occurred in 2006, 2007 and 2009 in the upper Adige River basin (Eastern Alps, northern Italy) have been analyzed. The first storm system (4 October 2006) generated a flash flood with almost no debris flows and landslides, the second (21 June 2007) triggered a large number of debris flows and was characterized by a relatively minor runoff response, and the third (4 September 2009) resulted in both a relevant flash flood response and debris flows in minor streams. A strong interest both for civil protection and research purposes has been devoted by local authorities and researchers to such events. The study methods include radar rainfall analysis, hydrological modeling and GIS processing of spatial rainfall data and debris-flow locations. Precise information on debris-flow location and related volumes were derived from a geo-spatial database of instability phenomena implemented and managed by the Autonomous Province of Bolzano. Patterns of rainfall distribution and relations between the main hydrological variables (cumulative rainfall, intensity and antecedent moisture) have been analyzed to explain differences in catchments responses between the three studied events. Radar rainfall data have permitted to analyze rainfall fields with high spatial resolution, taking into account also the elevation variability of rainfall rates. The striking responses' contrast among the three events is related to differences in antecedent moisture, space-time structure of the rainstorms, cumulative rainfall and intensity distributions and temperature regime. The frequency analysis of the main hydrological variables revealed to be a powerful tool capable of distinguishing, within a synoptic framework, the space-time-magnitude variability of the events, so as to highlight the differences in flood and debris-flow response.