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2. Evaluating historical, basin-wide landslide activity in a context of land abandonment and climate change: Effects of landslide visibility and temporal resolution

Author

Fondazione Cassa di Risparmio in Bologna, Ministero dell'Istruzione, dell'Università e della Ricerca, Pittau, Sharon, Rossi, Mauro, Llena, Manel, Brardinoni, Francesco, Fondazione Cassa di Risparmio in Bologna, Ministero dell'Istruzione, dell'Università e della Ricerca, Pittau, Sharon, Rossi, Mauro, Llena, Manel, and Brardinoni, Francesco

Abstract

Drainage basins of the Northern Apennines, particularly in the clayey settings, bear among the highest rates of landsliding worldwide. A history of major land cover changes has left a landscape characterized by sparse, coppice-managed forest, transitional shrubs, and actively eroding badlands. Historical trends of landslide occurrence are examined in the Sillaro River basin (139 km2) in relation to land cover and climatic changes. To this purpose we have compiled a multi-temporal (1954–2018) landslide inventory (n = 1164) across twelve sequential photo sets that bears decadal (7- to 15-yr) and finer (2- to 6-yr) temporal resolution respectively before and after 1996. To account for changes in meteorological forcing, we examine: (i) the total annual precipitation (PRCPTOT); (ii) the annual maximum daily precipitation (RX1day); and (iii) the precipitation fraction (R99pTOT) due to extremely wet days. We find that landslide activity is strongly controlled by lithology, with landslide densities in claystones 3-to-4 times higher than in marl-sandstone alternations. This difference is chiefly associated with badlands, which are the most active land cover type and where new scars at a site could recur up to nine times. To evaluate the influence of varying temporal resolution on inventory completeness, hence on inference about land cover and climatic effects, we constrain the time scales of landslide visibility and assess the relative rates of undersampling. We find that visibility functions decline non-linearly with time, and that an inventory compiled at 5-year resolution would be missing up to 20 % of the landslide scars, with the size of an additional 27 % that would be underestimated due to revegetation. Overall, detection of entire landslide scars, which varies with land cover, becomes rare after 13 years in transitional shrubs, and after 17 years in badlands and managed forest. The historical analysis shows that landslide count: (i) increases in 1955–1976, a period o

Published
2024

3. Characterization of a debris flow event using an affordable monitoring system

Author

Berti Matteo, Schimmel Andreas, Coviello Velio, Venturelli Mario, Albertelli Luca, Beretta Luca, Brardinoni Francesco, Ceriani Massimo, Pilotti Marco, Ranzi Roberto, Redaelli Marco, Scotti Riccardo, Simoni Alessandro, Turconi Laura, and Luino Fabio

Subjects
Environmental sciences, GE1-350
Abstract

This study presents monitoring data of a debris flow event in the Central Italian Alps. The debris flow occurred on August 16, 2021 in the Blè basin (Val Camonica valley, Lombardia Region) and was recorded by a monitoring station installed just few weeks before. The monitoring system was deployed to document the hydrologic response of the catchment to rainfall, and was designed to be lightweight, relatively cheap, and easy to deploy in the field. To this purpose, we combined video cameras with geophysical sensors (geophones and infrasound) and optimized the power supply system. The data recorded during the event allowed to identify the triggering rainfall, document the flow behaviour, and estimate surface flow velocity and flow rate using Particle Image Velocimetry algorithms. Moreover, the seismic signal generated by the debris flow revealed a peculiar frequency spectrum compared to regular streamflow. These results show that even a relatively simple monitoring system may provide valuable data on real debris flow events.

Published
2023
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5. A climate-driven, altitudinal transition in rock glacier dynamics detected through integration of geomorphological mapping and synthetic aperture radar interferometry (InSAR)-based kinematics.

Author

Bertone, Aldo, Jones, Nina, Mair, Volkmar, Scotti, Riccardo, Strozzi, Tazio, and Brardinoni, Francesco

Subjects
ROCK glaciers, RADAR interferometry, SYNTHETIC aperture radar, GEOMORPHOLOGICAL mapping, SYNTHETIC apertures, GLOBAL warming, KINEMATICS
Abstract

In dry southwestern South Tyrol, Italy, rock glaciers are dominant landforms of the high-mountain cryosphere. Their spatial distribution and degree of activity hold critical information on the current state of discontinuous permafrost and consequently on the response potential to climate warming. Traditional geomorphologic mapping, however, owing to the qualitative expert-based nature, typically displays a high degree of uncertainty and variability among operators with respect to the dynamic classification of intact (permafrost-bearing) and relict (permafrost-devoid) rock glaciers. This limits the reliability of geomorphologic rock glacier inventories for basic and applied purposes. To address this limitation, (i) we conduct a systematic evaluation of the improvements that synthetic aperture radar interferometry (InSAR) can afford to the detection and dynamic classification of rock glaciers and (ii) build an integrated inventory that combines the strengths of geomorphologic- and InSAR-based approaches. To exploit fully InSAR-based information towards a better understanding of the topo-climatic conditions that sustain creeping permafrost, we further explore how velocity and the spatial distribution of moving areas (MAs) within rock glaciers may vary as a function of simple topographic variables known to exert first-order controls on incoming solar radiation, such as elevation and aspect. Starting from a geomorphologic inventory (n=789), we characterize the kinematics of InSAR-based MAs and the relevant hosting rock glaciers on 36 Sentinel-1 interferograms in the 2018–2019 period. With respect to the original inventory, InSAR analysis allowed us to identify 14 previously undetected rock glaciers. Further, it confirmed that 246 (76 %) landforms, originally interpreted as intact, do exhibit detectable movement (i.e., ≥1 cm yr -1) and that 270 (60 %) of the relict labeled counterparts do not, whereas 144 (18 %) were kinematically undefined due to decorrelation. Most importantly, InSAR proved critical for reclassifying 121 (15 %) rock glaciers, clarifying that 41 (13 %) of those interpreted as being intact do not exhibit detectable movement and that 80 (17 %) of the original relict ones do move. Reclassification (i) allowed us to identify a cluster of intact rock glaciers below 2000 m a.s.l. associated with positive mean annual air temperature (MAAT), and (ii) by increasing the altitudinal overlap between intact and relict rock glaciers, it depicts a broad transition belt in the aspect–elevation space, which varies from 50 m on west-facing slopes to 500 m on easterly ones. This finding deteriorates the significance of elevation and aspect as topographic proxies for modeling permafrost occurrence and highlights the importance of using InSAR to inform such models. From a process-oriented standpoint, InSAR information proves fundamental for imaging how this altitudinal transition manifests through changing rates and styles of rock glacier surface deformation. Specifically, we find that, as rock glaciers move faster, an increasingly larger proportion of their surface becomes kinematically involved (i.e., percent MA cover) and that this proportion increases with elevation up to 2600–2800 m, beyond which an inflection occurs and consistent average values are attained. Considering that the inflection falls between the -1 and -2 °C MAAT – the lower boundary for discontinuous permafrost – and is independent of slope gradient, we conclude that this altitudinal pattern represents a geomorphic signature: the dynamic expression of increasing permafrost distribution, from sporadic to discontinuous. [ABSTRACT FROM AUTHOR]

Published
2024
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10. A climate-driven, altitudinal transition in rock glacier dynamics detected through integration of geomorphological mapping and InSAR-based kinematics.

Author

Bertone, Aldo, Jones, Nina, Mair, Volkmar, Scotti, Riccardo, Strozzi, Tazio, and Brardinoni, Francesco

Abstract

In dry southwestern South Tyrol, Italy, rock glaciers are dominant landforms of the high-mountain cryosphere. Their spatial distribution and degree of activity hold critical information on the past and current state of discontinuous permafrost, and consequently on response potential to climate warming. Traditional geomorphologic mapping, however, owing to the qualitative expert-based nature, typically displays a high degree of uncertainty and variability among operators with respect to the dynamic classification of intact (permafrost bearing) and relict (permafrost devoid) rock glaciers. This limits the reliability of geomorphologic rock glacier inventories for basic and applied purposes. To address this limitation: (i) we conduct a systematic evaluation of the improvements that InSAR-based information can afford to the detection and dynamic classification of rock glaciers; and (ii) build an integrated inventory that wishes to combine the strengths of geomorphologic- and InSAR-based approaches. To exploit fully InSAR-based information towards a better understanding of the topo-climatic conditions that sustain creeping permafrost, we further explore how velocity and the spatial distribution of moving areas (MAs) within rock glaciers may vary as a function of simple topographic variables known to exert first-order controls on incoming solar radiation, such as elevation and aspect. Starting from the compilation of a geomorphologic inventory (n = 789), we characterize the kinematics of InSAR-based MAs and the relevant hosting rock glaciers on thirty-six Sentinel-1 interferograms computed over 6-through 342-day baselines in the 2018-19 period. With respect to the original inventory, InSAR analysis allowed identifying 14 previously undetected rock glaciers. Further, it confirmed that 246 (76%) landforms, originally interpreted as intact, do exhibit detectable movement (i.e., =1 cm yr-1), and that 270 (60%) of the relict labelled counterparts do not, whereas 144 (18 %) resulted kinematically undefined due to decorrelation. Most importantly, InSAR proved critical for reclassifying 121 (15%) rock glaciers, clarifying that 41 (13%) of those interpreted as intact, do not exhibit detectable movement, and that 80 (17%) of the original relict ones do actually move. Reclassification, by increasing the altitudinal overlap between intact and relict rock glaciers depicts a broad transition belt in the aspect-elevation space, the amplitude of which varies from as little as 50 m on west facing slopes to a maximum of 500 m on easterly ones. This finding deteriorates the significance of elevation and aspect as topographic proxies for modelling permafrost occurrence, and highlights the importance of using InSAR for informing such models. From a process-oriented standpoint, InSAR information proves fundamental for imaging how this altitudinal transition manifests through changing rates and styles of rock glacier surface deformation. Specifically, we find that as rock glaciers move faster, an increasingly larger proportion of their surface becomes kinematically involved (i.e., percent MA cover), and that this proportion increases with elevation up to the 2600-2800 m, beyond which an inflection occurs and consistent average values are attained. Considering that the inflection falls between the -1°C and -2 °C MAAT - the lower boundary for discontinuous permafrost - and is independent of slope gradient, we conclude that this altitudinal pattern represents a geomorphic signature: the dynamic expression of increasing permafrost distribution (i.e., from sporadic to discontinuous), until optimal thermal conditions are reached. [ABSTRACT FROM AUTHOR]

Published
2023
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11. Sediment characterisation and analysis - WP 5 & WP 6 report SedInOut Project

Author

Mair, Volkmar, Rabanser, Monika, Scotti, Riccardo, and Brardinoni, Francesco

Abstract

Contemporary atmospheric temperature rise imposes profound physical changes to high- elevation mountain environments. These changes, by directly affecting the mountain cryosphere through glacier retreat and permafrost degradation, can alter the hydrologic regime of mountain drainage basins (Huggel et al., 2015), as well as the amount and caliber of sediment readily available for mass movements and fluvial transport. Although sediment supply exerts a primary control on channel stability and relevant geo-hazard potential, there is a general lack of standard procedures for characterizing sediment sources, sediment typology and for evaluating sediment availability. This gap, which is mainly associated with the variety of existing national and regional protocols of data collection, currently prevents pursuing an unbiased, transnational risk management strategy considering current climatic challenges. SedInOut, through a joint international effort, aims to develop methodologies for the quantification and characterization of sediment across representative pilot catchments, towards a sustainable land management that values geo-risk mitigation and sediment recycling. In this report, we present a methodological approach that relies on existing geological mapping (CARG project), high-resolution digital topography, and historical aerial photos and orthophoto mosaics, while integrating field-based and proximal sensing data in conjunction with multi- temporal, remotely based mapping (Figure 1).Remotely sensed procedures include multi- temporal mapping of glacier extent (Section 3.1.1), Quaternary materials (e.g., bedrock, glacial till, talus debris, colluvium, and alluvium) (Section 3.1.2), the drainage network (Section 3.1.3) and rapid shallow failures (i.e., sediment sources including debris slides, debris flows and bank collapses) (Section 3.1.4). Field-based and proximal sensing data include measurements on shallow landslide geometry (Section 3.2.1), and characterization of surface (i.e., manual Wolman pebble count and photo sieving) and subsurface (i.e., bulk sampling, on-site preliminary sieving, and laboratory sieving) grain size distribution (GSD) conducted at six representative sites (i.e., M1 through M6;Figure 2a) along the mountain channel network that drains the glaciated landscape of Upper Mazia Valley (Sections 3.2.2,3.2.3,3.3, and3.4). Field measurements on landslide geometry are critical for constraining an empirical landslide area-volume relation, which in turn is used for translating landslide areas, as mapped on sequential photo sets, into first-order volumetric estimates of mobilized debris. GSD data allows characterizing the spatial variability of characteristic sediment calibers (i.e., D50, D84, and D90) as well as the armoring ratio (an index of channel stability), starting at glacier and rock glacier fronts and moving downstream. The multi-temporal mapping approach is structured as follows. Through visual inspection of sequential orthophoto sets, we first track changes in glacier extent. Subsequently, as glaciers retreat, we map and quantify the extent of newly exposed Quaternary materials, the occurrence of shallow rapid failures, and the relevant changes in the structure of the main drainage network. In this document, we illustrate SedInOut methodological approach applied to Mazia Valley, here regarded as representative of conditions that characterize the Austroalpine geologic domain. In particular, we integrate two nested spatial scales: (i)Upper Mazia Valley(18.8 km2) over which we conducted extensive fieldwork to constrain the geometry of rapid shallow failures on the hillslopes and low-order streams, and to characterize alluvial sediment along the channel network(Figure 2a); (ii)Proglacial Mazia Area(8.4 km2), where we document decadal geomorphological changes following the retreat of the Mazia glacier (Figure 2b). Time and temporal scales of investigation are summarized inTable 1.

Published
2023
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12. Caratterizzazione e analisi del sedimento - WP 5 & WP 6 report Progetto SedInOut

Author

Mair, Volkmar, Rabanser, Monika, Scotti, Riccardo, and Brardinoni, Francesco

Abstract

Il recente incremento della temperatura atmosferica è causa di profondi cambiamenti in ambienti montani di alta quota. Tali cambiamenti, influenzando direttamente la criosfera montana attraverso il ritiro dei ghiacciai e la degradazione del permafrost, possono alterare il regime idrologico dei bacini montani (Huggel et al., 2015), nonché la quantità e il calibro del sedimento disponibile per i movimenti di massa e il trasporto fluviale. Sebbene l'apporto di sedimento eserciti un controllo primario sulla stabilità dei canali e sul relativo potenziale rischio geologico, si nota una mancanza generale di procedure standard per la caratterizzazione di sorgenti e tipologia del sedimento, nonché per la valutazione della sua disponibilità. Questa lacuna, che è principalmente associata alla varietà dei protocolli nazionali e regionali esistenti per la raccolta dei dati, attualmente impedisce di perseguire una strategia di gestione del rischio oggettiva e transnazionale alla luce delle attuali sfide climatiche. SedInOut, attraverso uno sforzo interregionale congiunto, mira a sviluppare metodologie per la quantificazione e la caratterizzazione del sedimento in bacini idrografici rappresentativi, verso una gestione sostenibile del territorio che valorizzi la mitigazione del rischio geologico e l‘utilizzo del sedimento mobilizzato naturalmente. In questa relazione presentiamo un approccio metodologico che si basa sulla cartografia geologica esistente (progetto CARG), sulla topografia digitale ad alta risoluzione e sulle ortofotocarte storiche, integrando dati di rilevamento di campo e prossimali insieme a una mappatura multitemporale basata su metodi di telerilevamento (Figura 1). Le procedure di telerilevamento comprendono la mappatura multitemporale dell'estensione dei ghiacciai (sezione 3.1.1), dei depositi quaternari (ad es. roccia, till, detrito di versante, colluvium e alluvium) (sezione 3.1.2), del reticolo idrografico (sezione 3.1.3) e dei movimenti superficiali rapidi di versante, che per brevità, in questo documento verranno nominate come “frane rapide superficiali” (ad es. scivolamenti, colate di detrito e collassi spondali) (sezione 3.1.4). I dati di rilevamento sul campo e prossimali includono misurazioni sulla geometria delle frane poco profonde (sezione 3.2.1) e la caratterizzazione della granulometria superficiale (camminata casuale in stile Wolman e setacciatura basata su immagini) e subsuperficiale (ad esempio, campionamento ponderale, setacciatura meccanica preliminare in loco seguita da setacciatura in laboratorio) condotta in sei siti rappresentativi (da M1 a M6; Figura 2a) lungo il reticolo che drena il paesaggio glaciale dell'Alta Valle di Mazia (sezioni 3.2.2, 3.2.3, 3.3 e 3.4). Le misurazioni sul campo della geometria delle frane sono fondamentali per definire una relazione empirica area-volume, che a sua volta viene utilizzata per tradurre le aree di frana, mappate su set di foto sequenziali, in stime volumetriche del detrito mobilitato. I dati della distribuzione granulometrica consentono di caratterizzare la variabilità spaziale dei calibri di percentili caratteristici di una distribuzione granulometrica (D50, D84 e D90) e il rapporto di corazzamento (un indice di stabilità del canale), partendo dalle fronti dei ghiacciai e dei rock glacier, da cui i torrenti di studio si originano, e procedendo verso valle. L'approccio della mappatura multitemporale è strutturato come segue. Attraverso l'ispezione visiva di set di ortofotomosaici multitemporali, vengono tracciati i cambiamenti nell'estensione areale dei ghiacciai. Successivamente, con il ritiro dei ghiacciai, viene mappata e quantificata l'estensione dei materiali quaternari recentemente esposti e i relativi cambiamenti nella struttura del reticolo idrografico principale. In questo documento illustriamo l'approccio metodologico di SedInOut applicato alla Val di Mazia, considerata rappresentativa delle condizioni che caratterizzano il dominio geologico Austroalpino. In particolare, vengono integrate due scale spaziali: (i) l'Alta Val di Mazia (18,8 km2 ), in cui abbiamo condotto un'ampia attività di ricerca sul campo per definire la geometria delle frane rapide superficiali sui versanti e sui corsi d'acqua di basso ordine e per caratterizzare i sedimenti alluvionali lungo il reticolo idrografico (Figura 2a); (ii) l'Area Proglaciale di Mazia (8,4 km2 ), dove abbiamo documentato i cambiamenti geomorfologici decennali in seguito al ritiro del Ghiacciaio di Mazia (Figura 2b). Le scale temporali e spaziali di indagine sono riassunte in Tabella 1., La ricerca è stata finanziata dal Progetto Interreg V-A Italy – Austria ITAT3032 SedInOut – 'Development of a risk management methodology through the assessment of sediment availability for mass wasting in a mountain environment'

Published
2023
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13. Incorporating InSAR kinematics into rock glacier inventories: insights from 11 regions worldwide

Author

Bertone, Aldo, primary, Barboux, Chloé, additional, Bodin, Xavier, additional, Bolch, Tobias, additional, Brardinoni, Francesco, additional, Caduff, Rafael, additional, Christiansen, Hanne H., additional, Darrow, Margaret M., additional, Delaloye, Reynald, additional, Etzelmüller, Bernd, additional, Humlum, Ole, additional, Lambiel, Christophe, additional, Lilleøren, Karianne S., additional, Mair, Volkmar, additional, Pellegrinon, Gabriel, additional, Rouyet, Line, additional, Ruiz, Lucas, additional, and Strozzi, Tazio, additional

Published
2022
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14. Landslide activity in contrasting land-cover settings constrained by multi-temporal inventorying

Author

Brardinoni, Francesco, Pittau, Sharon <1992>, Brardinoni, Francesco, and Pittau, Sharon <1992>

Abstract

This doctoral thesis focuses on the study of historical shallow landslide activity over time in response to anthropogenic forcing on land use, through the compilation of multi-temporal landslide inventories. The study areas, located in contrasting settings and characterized by different history of land-cover changes, include the Sillaro River basin (Italy) and the Tsitika and Eve River basins (coastal British Columbia). The Sillaro River basin belongs to clay-dominated settings, characterized by extensive badland development, and dominated by earth slides and earthflows. Here, forest removal began in the Roman period and has been followed by agricultural land abandonment and natural revegetation in recent time. By contrast, the Tsitika-Eve River basins are characterized by granitic and basaltic lithologies, and dominated by debris slides, debris flows and debris avalanches. In this setting, anthropogenic impacts started in 1960’s and have involved logging operation. The thesis begins with an introductory chapter, followed by a methodological section, where a multi-temporal mapping approach is proposed and tested at four landslide sites of the Sillaro River basin. Results, in terms of inventory completeness in time and space, are compared against the existing region-wide Emilia-Romagna inventory. This approach is then applied at the Sillaro River basin scale, where the multi-temporal inventory obtained is used to investigate the landslide activity in relation to historical land cover changes across geologic domains and in relation to hydro-meteorological forcing. Then, the impact of timber harvesting and road construction on landslide activity and sediment transfer in the Tsitika-Eve River basins is investigated, with a focus on the controls that interactions between landscape morphometry and cutblock location may have on landslide size-frequency relations. The thesis ends with a summary of the main findings and discusses advantages and limitations associated with th

Published
2022

17. Supplementary material to "Incorporating kinematic attributes into rock glacier inventories exploiting InSAR data: preliminary results in eleven regions worldwide"

Author

Bertone, Aldo, primary, Barboux, Chloé, additional, Bodin, Xavier, additional, Bolch, Tobias, additional, Brardinoni, Francesco, additional, Caduff, Rafael, additional, Christiansen, Hanne Hvidtfeldt, additional, Darrow, Margaret, additional, Delaloye, Reynald, additional, Etzelmüller, Bernd, additional, Humlum, Ole, additional, Lambiel, Christophe, additional, Lilleøren, Karianne Staalesen, additional, Mair, Volkmar, additional, Pellegrinon, Gabriel, additional, Rouyet, Line, additional, Ruiz, Lucas, additional, and Strozzi, Tazio, additional

Published
2022
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18. Incorporating kinematic attributes into rock glacier inventories exploiting InSAR data: preliminary results in eleven regions worldwide

Author

Bertone, Aldo, primary, Barboux, Chloé, additional, Bodin, Xavier, additional, Bolch, Tobias, additional, Brardinoni, Francesco, additional, Caduff, Rafael, additional, Christiansen, Hanne Hvidtfeldt, additional, Darrow, Margaret, additional, Delaloye, Reynald, additional, Etzelmüller, Bernd, additional, Humlum, Ole, additional, Lambiel, Christophe, additional, Lilleøren, Karianne Staalesen, additional, Mair, Volkmar, additional, Pellegrinon, Gabriel, additional, Rouyet, Line, additional, Ruiz, Lucas, additional, and Strozzi, Tazio, additional

Published
2022
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22. Variable hillslope-channel coupling and channel characteristics of forested mountain streams in glaciated landscapes

Author

Hassan, Marwan A., Bird, Stephen, Reid, David, Ferrer-Boix, Carles, Hogan, Dan, Brardinoni, Francesco, Chartrand, Shawn, Hassan, Marwan A., Bird, Stephen, Reid, David, Ferrer-Boix, Carle, Hogan, Dan, Brardinoni, Francesco, and Chartrand, Shawn

Subjects
landslide, channel classification, hydraulic geometry, mountain stream, process domain, divide breaching, glacial history, hillslope–channel coupling, wood
Abstract

Channel morphology of forested, mountain streams in glaciated landscapes is regulated by a complex suite of processes, and remains difficult to predict. Here, we analyze models of channel geometry against a comprehensive field dataset collected in two previously glaciated basins in Haida Gwaii, B.C., to explore the influence of variable hillslope–channel coupling imposed by the glacial legacy on channel form. Our objective is to better understand the relation between hillslope–channel coupling and stream character within glaciated basins. We find that the glacial legacy on landscape structure is characterized by relatively large spatial variation in hillslope–channel coupling. Spatial differences in coupling influence the frequency and magnitude of coarse sediment and woody material delivery to the channel network. Analyses using a model for channel gradient and multiple models for width and depth show that hillslope–channel coupling and high wood loading induce deviations from standard downstream predictions for all three variables in the study basins. Examination of model residuals using Boosted Regression Trees and nine additional channel variables indicates that ~10 to ~40% of residual variance can be explained by logjam variables, ~15–40% by the degree of hillslope–channel coupling, and 10–20% by proximity to slope failures. These results indicate that channel classification systems incorporating hillslope–channel coupling, and, indirectly, the catchment glacial legacy, may present a more complete understanding of mountain channels. From these results, we propose a conceptual framework which describes the linkages between landscape history, hillslope–channel coupling, and channel form. © 2018 John Wiley & Sons, Ltd.

Published
2019

26. Un approccio multiscala alle dinamiche fluviali di alvei montani

Author

Brardinoni, Francesco, Balzano, Mariateresa <1989>, Brardinoni, Francesco, and Balzano, Mariateresa <1989>

Abstract

Questo lavoro di tesi è finalizzato allo studio delle morfodinamiche fluviali in ambiente montano, in risposta a forzanti antropiche e naturali. In particolare, si prendono in considerazione sistemi Appenninici (i.e., Fiume Santerno) e Alpini (i.e., Rii Grigno, Tolvà e Ussaia), integrando due approcci che si sviluppano su scale spazio-temporali differenti. Nel caso Appenninico vengono esaminati i cambiamenti planimetrici dell’alveo attivo del Fiume Santerno in risposta ad impatti antropici, quali l’estrazione di inerti in alveo, la costruzione di opere idrauliche e l’alterazione di uso del suolo a scala di bacino. Nei tre casi Alpini, che si differenziano in termini di forzante idro-meteorologica ed apporto di sedimento da monte, si è valutato il trasporto solido di fondo (bedload transport) mediante tecnologia RFID., The present study refers to the fluvial morphodynamics study in mountain environments by a multi-scale approach.

Published
2020

33. Indices of sediment connectivity: opportunities, challenges and limitations

Author

UCL - SST/ELI/ELIE - Environmental Sciences, Heckmann, Tobias, Cavalli, Marco, Cerdan, Olivier, Foerster, Saskia, Javaux, Mathieu, Lode, Elve, Smetanová, Anna, Vericat, Damià, Brardinoni, Francesco, UCL - SST/ELI/ELIE - Environmental Sciences, Heckmann, Tobias, Cavalli, Marco, Cerdan, Olivier, Foerster, Saskia, Javaux, Mathieu, Lode, Elve, Smetanová, Anna, Vericat, Damià, and Brardinoni, Francesco

Abstract

Indices of connectivity are critical means for moving from qualitative to (semi-)quantitative evaluations of material (e.g., water, sediment and nutrients) transfer across the building blocks of a terrestrial system. In geomorphology, compared to closely related disciplines like ecology and hydrology, the development of indices has only recently started and as such presents opportunities and challenges that merit attention. In this paper, we review existing indices of sediment connectivity and suggest potential avenues of development for meeting current basic and applied research needs. Specifically, we focus on terrestrial geomorphic systems dominated by processes that are driven by hydro-meteorological forcing, neglecting seismically triggered events, karstic systems and environments controlled by eolian processes. We begin by setting a conceptual framework that combines external forcings (drivers) and system (intrinsic) structural and functional properties relevant to sediment connectivity. This framework guides our review of response variables suitable for sediment connectivity indices. In particular, we consider three sample applications concerned with sediment connectivity in: (i) soil studies at the plot scale, (ii) bedload transport at the reach scale, and (iii) sediment budgets at the catchment scale. In relation to the set of response variables identified, we consider data availability and issues of data acquisition for use in indices of sediment connectivity. We classify currently available indices in raster based, object or network based, and indices based on effective catchment area. Virtually all existing indices address the degree of static, structural connectivity only, with limited attention for process-based, functional connectivity counterparts. Most recent developments in indices of sediment connectivity deal, to some extent, with different styles of anthropogenic and hydro-meteorological forcings and with the temporal variability of sediment con

Published
2018

34. Evaluating debris‐flow and anthropogenic disturbance on 10Be concentration in mountain drainage basins: implications for functional connectivity and denudation rates across time scales.

Author

Brardinoni, Francesco, Grischott, Reto, Kober, Florian, Morelli, Corrado, and Christl, Marcus

Subjects
FUNCTIONAL connectivity, WATERSHEDS, LAST Glacial Maximum, DIVERSION structures (Hydraulic engineering), HYDRAULIC structures
Abstract

We examine the sensitivity of 10Be concentrations (and derived denudation rates), to debris‐flow and anthropogenic perturbations in steep settings of the Eastern Alps, and explore possible relations with structural geomorphic connectivity. Using cosmogenic 10Be as a tracer for functional geomorphic connectivity, we conduct sampling replications across four seasons in Gadria, Strimm and Allitz Creek. Sampling sites encompass a range of structural connectivity configurations, including the conditioning of a sackung, all assessed through a geomorphometric index (IC). By combining information on contemporary depth of erosion and sediment yield, disturbance history and post‐LGM (Last Glacial Maximum) sedimentation rates, we constrain the effects of debris‐flow disturbance on 10Be concentrations at the Gadria sites. Here, we argue that bedrock weakening imparted by the sackung promotes high depth of erosion. Consequently, debris flows recruit sediment beyond the critical depth of spallogenic production (e.g., >3 m), which in turn, episodically, due to predominantly muogenic production pathways, lowers 10Be concentration by a factor of 4, for at least 2 years. In contrast, steady erosion in Strimm Creek yields very stable 10Be concentrations through time. In Allitz Creek, we observe two‐ to fourfold seasonal fluctuations in 10Be concentrations, which we explain as the combined effects of water diversion and hydraulic structures on sediment mixing. We further show that 10Be concentration correlates inversely with the IC index, where sub‐basins characterized by high concentrations (long residence times) exhibit low IC values (structurally disconnected) and vice versa, implying that, over millennial time scales a direct relation exists between functional and structural connectivity, and that the IC index performed as a suitable metric for structural connectivity. The index performs comparably better than other metrics (i.e., mean slope and mean normalized channel steepness index) previously used to assess topographic controls on denudation rates in active unglaciated ranges. In terms of landscape evolution, we argue that the sackung, by favouring intense debris‐flow activity across the Holocene, has aided rapid postglacial reshaping of the Gadria basin, which currently exhibits a topographic signature characteristic of unglaciated debris‐flow systems. © 2020 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Published
2020
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39. Time constrains for post-LGM landscape response to deglaciation in Val Viola, Central Italian Alps

Author

Scotti, R, Brardinoni, F, Crosta, G, Cola, G, Mair, V, Scotti, Riccardo, Brardinoni, Francesco, Crosta, Giovanni Battista, Cola, Giuseppe, Mair, Volkmar, Scotti, R, Brardinoni, F, Crosta, G, Cola, G, Mair, V, Scotti, Riccardo, Brardinoni, Francesco, Crosta, Giovanni Battista, Cola, Giuseppe, and Mair, Volkmar

Abstract

Across the northern European Alps, a long tradition of Quaternary studies has constrained post-LGM (Last Glacial Maximum) landscape history. The same picture remains largely unknown for the southern portion of the orogen. In this work, starting from existing10Be exposure dating of three boulders in Val Viola, Central Italian Alps, we present the first detailed, post-LGM reconstruction of landscape (i.e., glacial, periglacial and paraglacial) response south of the Alpine divide. We pursue this task through Schmidt-hammer exposure-age dating (SHD) at 34 sites including moraines, rock glaciers, protalus ramparts, rock avalanche deposits and talus cones. In addition, based on the mapping of preserved moraines and on the numerical SHD ages, we reconstruct the glacier extent of four different stadials, including Egesen I (13.1 ± 1.1 ka), Egesen II (12.3 ± 0.6 ka), Kartell (11.0 ± 1.4 ka) and Kromer (9.7 ± 1.4 ka), whose chronologies agree with available counterparts from north of the Alpine divide. Results show that Equilibrium Line Altitude depressions (ΔELAs) associated to Younger Dryas and Early Holocene stadials are smaller than documented at most available sites in the northern Alps. These findings not only support the hypothesis of a dominant north westerly atmospheric circulation during the Younger Dryas, but also suggest that this pattern could have lasted until the Early Holocene. SHD ages on rock glaciers and protalus ramparts indicate that favourable conditions to periglacial landform development occurred during the Younger Dryas (12.7 ± 1.1 ka), on the valley slopes above the glacier, as well as in newly de-glaciated areas, during the Early Holocene (10.7 ± 1.3 and 8.8 ± 1.8 ka). The currently active rock glacier started to develop before 3.7 ± 0.8 ka and can be associated to the Löbben oscillation. Four of the five rock avalanches dated in Val Viola cluster within the Early Holocene, in correspondence of an atmospheric warming phase. By co

Published
2017

41. Patterns of bedload entrainment and transport in forested headwater streams of the Columbia Mountains, Canada

Author

Green, K, Alila, Y., BRARDINONI, FRANCESCO, Green, K, Alila, Y, Brardinoni, F, Alila, Y., and Brardinoni, F.

Subjects
rating curve, Earth-Surface Processe, Geography, Planning and Development, transport formulae, Earth and Planetary Sciences (miscellaneous), bedload transport, resistance to flow, bedload entrainment
Abstract

We monitor bedload transport and water discharge at six stations in two forested headwater streams of the Columbia Mountains, Canada. The nested monitoring network is designed to examine the effects of channel bed texture, and the influence of alluvial (i.e.step pools and riffle pools) and semialluvial morphologies (i.e.boulder cascades and forced step pools) on bedload entrainment and transport. Results indicate that dynamics of bedload entrainment are influenced by differences in flow resistance attributable to morphology. Scaled fractional analysis shows that in reaches with high form resistance most bedload transport occurs in partial mobility fashion relative to the available bed material, while calibers finer than 16mm attain full mobility during bankfull flows. Equal mobility transport for a wider range of grain sizes is achieved in reaches exhibiting reduced form resistance. Our findings confirm that the Shields value for mobilization of the median surface grain size depends on channel gradient and relative submergence; however, we also find that these relations vary considerably for cobble and gravel bed channels due to proportionality between dimensionless shear stress and grain size. Exponents of bedload rating curves across sites correlate most with the D90s of the mobile bed, however, where grain effects are controlled (i.e.along individual streams), differences in form resistance across morphologies exert a primary control on bedload transport dynamics. Application of empirical formulae developed for use in steep alpine channels present variable success in predicting transport rates in forested snowmelt streams. Formulae that explicitly account for reductions in mobile bed area and high morphological resistance associated with woody debris provide the best approximation to observed empirical data.

Published
2015

42. Tracing bedload transport in Alpine mountain streams by means of PIT-tagged particles: interplay between sediment supply and hydro-meteorological forcing

Author

Fraccarollo, Luigi, Brardinoni, Francesco, Toro, Matteo, Fraccarollo, Luigi, Brardinoni, Francesco, and Toro, Matteo

Abstract

Conceptual models of first-order controls governing river channel dynamics in mountain streams have been rarely tested in the field. In this Ph.D. thesis we examine the effects of hydro-meteorological forcing and sediment supply on the bedload transport dynamics of mountain streams. To this purpose we select three step-pool mountain streams that share identical granitic lithology, but exhibit contrasting sediment supply and hydro-climatic conditions. The three study sites, which are located in Trentino, Eastern Italian Alps, include the Ussaia Creek (2.3 km2) in Val di Sole, and the Grigno and Tolvà Creeks (7 km2) in Valsugana. The former is characterized by high, sand-rich sediment supply delivered by some 20 m-thick glacigenic deposits. The latter two, which flow through glacially carved bedrock terrain, are disconnected from colluvial sediment inputs so that sediment sources are limited to channel banks and bars during high flows. Mean annual precipitation is respectively 844 mm in Ussaia Creek and 1511 mm in Grigno and Tolvà Creeks. All study streams experience, to variable extents, snowmelt and rainfall-induced bedload transporting flows. To estimate quantitatively the effects and the interactions associated with sediment supply and hydro-meteorological forcing, we monitor precipitation and atmospheric temperature. Hydrological levels at instrumented sections are recorded via pressure transducers. Bedload transport is monitored by tagging and tracking 632 stones (b-axis: 30 to 131 mm; weight 88-4004 g). The tracking of these PIT-tagged tracers was conducted from December 2013 to December 2015 by means of an RFID portable pole antenna. Cumulatively, a total of 16, 11 and 19 bedload events were monitored respectively at Grigno, Tolvà and Ussaia Creek. We measured displacement lengths occurred during inter-survey periods, induced by peak flows associated to snowmelt, rainfall or a combination of the two (mixed-type). Active channel depth was evaluated via direct d

Published
2016

43. Inherited anthropogenic disturbance and decadal sediment dynamics in a mountain fluvial system: The case of the Marecchia River canyon, Northern Apennines.

Author

Llena, Manel, Simonelli, Tommaso, and Brardinoni, Francesco

Subjects
*AGGRADATION & degradation, *RIVER channels, *FLUVIAL geomorphology, *SEDIMENTS, *DIGITAL elevation models
Abstract

We evaluate decadal coarse sediment dynamics along the Marecchia River of the Northern Apennines, a fluvial system with a history of gravel mining that led to the incision of a 6-km-long canyon. To this purpose, we subdivided the river into 21 reaches, seen as sediment reservoirs, to examine (1) historical variations in active channel width (1955-2019) in conjunction with (2) change in alluvial sediment storage (2009-2019), by differencing two sequential LiDAR digital elevation models (DEMs) within the active channel footprint. Combined examination of lateral (widening or narrowing) and vertical (aggradation or degradation) channel changes allowed the identification of composite styles of reservoir adjustment, as well as the refinement of geomorphic inference solely based on changes in active channel width. In particular, we find that different styles of decadal adjustment (1) are compatible with supply- and transport-limited conditions, as constrained by degree of confinement, stream channel slope, and active channel width; and (2) indicate different stages of evolution at reservoirs located upstream and downstream of the canyon head (dynamic equilibrium vs. transient response). The persistence of this geomorphic divide is supported over historical time scales by distinctive trends in planform channel changes, suggesting that sedimentary signal propagation downstream becomes abruptly interrupted at the canyon head. Over this 10-year natural experiment, the spatial pattern of erosion along the canyon exemplifies a striking case of transient response to anthropogenic forcing, where decadal topographic change, modulated by varying styles of hillslope-channel coupling, declines nonlinearly downstream. Depth of incision along the canyon increases progressively upstream, suggesting that the canyon head has been evolving toward a more unstable configuration with no significant change in sediment supply. This tendency, which points to a possible runaway style of development as bedload wearing on weak pelitic side walls continues, may hold basic implications for our understanding of channel incision into bedrock and strath terrace formation. [ABSTRACT FROM AUTHOR]

Published
2024
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45. Landslide activity in contrasting land-cover settings constrained by multi-temporal inventorying

Author

Pittau, Sharon <1992> and Brardinoni, Francesco

Subjects
GEO/04 Geografia fisica e geomorfologia
Abstract

This doctoral thesis focuses on the study of historical shallow landslide activity over time in response to anthropogenic forcing on land use, through the compilation of multi-temporal landslide inventories. The study areas, located in contrasting settings and characterized by different history of land-cover changes, include the Sillaro River basin (Italy) and the Tsitika and Eve River basins (coastal British Columbia). The Sillaro River basin belongs to clay-dominated settings, characterized by extensive badland development, and dominated by earth slides and earthflows. Here, forest removal began in the Roman period and has been followed by agricultural land abandonment and natural revegetation in recent time. By contrast, the Tsitika-Eve River basins are characterized by granitic and basaltic lithologies, and dominated by debris slides, debris flows and debris avalanches. In this setting, anthropogenic impacts started in 1960’s and have involved logging operation. The thesis begins with an introductory chapter, followed by a methodological section, where a multi-temporal mapping approach is proposed and tested at four landslide sites of the Sillaro River basin. Results, in terms of inventory completeness in time and space, are compared against the existing region-wide Emilia-Romagna inventory. This approach is then applied at the Sillaro River basin scale, where the multi-temporal inventory obtained is used to investigate the landslide activity in relation to historical land cover changes across geologic domains and in relation to hydro-meteorological forcing. Then, the impact of timber harvesting and road construction on landslide activity and sediment transfer in the Tsitika-Eve River basins is investigated, with a focus on the controls that interactions between landscape morphometry and cutblock location may have on landslide size-frequency relations. The thesis ends with a summary of the main findings and discusses advantages and limitations associated with the compilation of multi-temporal inventories in the two settings during different periods of human-driven, land-cover dynamics.

Published
2022

46. A multi-scale approach to evaluate fluvial morphodynamics in mountain environments

Author

Balzano, Mariateresa and Brardinoni, Francesco

Subjects
GEO/04 Geografia fisica e geomorfologia
Abstract

Questo lavoro di tesi è finalizzato allo studio delle morfodinamiche fluviali in ambiente montano, in risposta a forzanti antropiche e naturali. In particolare, si prendono in considerazione sistemi Appenninici (i.e., Fiume Santerno) e Alpini (i.e., Rii Grigno, Tolvà e Ussaia), integrando due approcci che si sviluppano su scale spazio-temporali differenti. Nel caso Appenninico vengono esaminati i cambiamenti planimetrici dell’alveo attivo del Fiume Santerno in risposta ad impatti antropici, quali l’estrazione di inerti in alveo, la costruzione di opere idrauliche e l’alterazione di uso del suolo a scala di bacino. Nei tre casi Alpini, che si differenziano in termini di forzante idro-meteorologica ed apporto di sedimento da monte, si è valutato il trasporto solido di fondo (bedload transport) mediante tecnologia RFID., The present study refers to the fluvial morphodynamics study in mountain environments by a multi-scale approach.

Published
2020

47. Multi-risk and interdependency modeling: The case of landslide triggering by earthquakes and other phenomena

Author

Jafarimanesh, Ahoura, Giardini, Domenico, Mignan, A., Ivy-Ochs, Susan, and Brardinoni, Francesco

Subjects
Physics, Generalities, science, Data processing, computer science, Earth sciences, Natural sciences, FOS: Mathematics, ddc:000, ddc:550, ddc:530, ddc:500, Landslides, Risk, Multi-risk, Multi-hazard, Earthquake, Climate change, Weather, Rainfall, Natural hazards, Risk modeling, Multi-risk assessments, Geophysics, Geotechnical Engineering, Hydro-geological risk assessment, Civil Engineering, Environmental Engineering, Seismology, Cellular Automata, Computer science, self-organised criticality, Slope Stability, Risk harmonisation, Risk management, Risk mitigation, Earthquake disaster, Statistical sciences, Statistical modeling, machine learning, Climate models, Landslide forecasting, Hazard footprint, Loss estimate, Loss curves, Risk curves, Probabilistic modeling, Seismic hazard, Seismic risk, Landslide Risk, Catastrophe modeling, Risk mitigation, Nat Cat data analysis, Geothermal energy, Hydraulic energy, Decision-making, Induced seismicity, Machine learning, Energy research, Exceedance probability curve, Probabilistic analysis, Data modeling, Database management, ddc:004, ddc:510, FOS: Natural sciences, Mathematics
Published
2020

48. Evaluating millennial to contemporary time scales of glacier change in Val Viola, Central Italian Alps

Author

R. Scotti, Francesco Brardinoni, Scotti, Riccardo, and Brardinoni, Francesco

Subjects
010506 paleontology, geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, biology, Lateglacial, Geography, Planning and Development, Geology, Glacier, European Alp, Forcing (mathematics), Climate–glacier decoupling, biology.organism_classification, 01 natural sciences, paleo-climate, Paleoclimatology, Little Ice Age, Deglaciation, Glacier fluctuation, Physical geography, Little ice age, 0105 earth and related environmental sciences, Viola (butterfly)
Abstract

To improve current understanding of ongoing deglaciation dynamics in relation to climatic forcing, it is critical to build long-term series of climate and glacier changes. This task is typically hampered by availability and resolution of Quaternary glacier paleo-reconstructions. To explore opportunities and challenges, we present a case study from Val Viola, which integrates area, volume and ELA changes across a 13k-year time window, including four Younger Dryas–Early Holocene glacier stadials and eight post-LIA periods. Results suggest that relevant shifts in climatic forcing associated with the Pleistocene–Holocene transition and post-LIA deglaciation phases are of comparable magnitude, with an atmospheric temperature increase of about 1.5–2°C. Post-LIA decline in glacierized areas (68.9 ± 6%) is comparable with retreat rates recorded in other Italian glaciers, but is greater than elsewhere in the Alps, where glaciers are comparably larger. Glacier stability in the particularly warm 2007–2015 period testifies to the decoupling attained by small glaciers from synoptic atmospheric conditions. We argue that this is caused by enhanced wind drift and avalanche accumulation, occurred in response to morphological changes on ice surfaces following progressive glacier shrinking. This positive feedback not only could delay glacier extinction in certain physiographic settings but also could introduce bias in paleo-glaciological reconstructions of climatic conditions.

Published
2018

49. Indices of sediment connectivity: opportunities, challenges and limitations

Author

Olivier Cerdan, Anna Smetanova, Marco Cavalli, Saskia Foerster, Elve Lode, Mathieu Javaux, Francesco Brardinoni, Tobias Heckmann, Damià Vericat, Bureau de Recherches Géologiques et Minières (BRGM) (BRGM), Université Catholique de Louvain = Catholic University of Louvain (UCL), Technische Universität Berlin (TU), University of Lleida (UL), Heckmann, Tobias, Cavalli, Marco, Cerdan, Olivier, Foerster, Saskia, Javaux, Mathieu, Lode, Elve, Smetanová, Anna, Vericat, Damià, and Brardinoni, Francesco

Subjects
Response variables, 010504 meteorology & atmospheric sciences, Relation (database), 0208 environmental biotechnology, Geomorphic coupling, Scales, Context (language use), 02 engineering and technology, 01 natural sciences, Response variable, Applied research, Temporal scales, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, Forcing (recursion theory), Sediment transfer, Structural and functional connectivity, Sediment, Geomorphic systems, Field (geography), Scale, 020801 environmental engineering, [SDU]Sciences of the Universe [physics], 13. Climate action, Geomorphic system, [SDE]Environmental Sciences, General Earth and Planetary Sciences, Environmental science, Physical geography, Scale (map), Earth and Planetary Sciences (all)
Abstract

Indices of connectivity are critical means for moving from qualitative to (semi-)quantitative evaluations of material (e.g., water, sediment and nutrients) transfer across the building blocks of a terrestrial system. In geomorphology, compared to closely related disciplines like ecology and hydrology, the development of indices has only recently started and as such presents opportunities and challenges that merit attention. In this paper, we review existing indices of sediment connectivity and suggest potential avenues of development for meeting current basic and applied research needs. Specifically, we focus on terrestrial geomorphic systems dominated by processes that are driven by hydro-meteorological forcing, neglecting seismically triggered events, karstic systems and environments controlled by eolian processes. We begin by setting a conceptual framework that combines external forcings (drivers) and system (intrinsic) structural and functional properties relevant to sediment connectivity. This framework guides our review of response variables suitable for sediment connectivity indices. In particular, we consider three sample applications concerned with sediment connectivity in: (i) soil studies at the plot scale, (ii) bedload transport at the reach scale, and (iii) sediment budgets at the catchment scale. In relation to the set of response variables identified, we consider data availability and issues of data acquisition for use in indices of sediment connectivity. We classify currently available indices in raster based, object or network based, and indices based on effective catchment area. Virtually all existing indices address the degree of static, structural connectivity only, with limited attention for process-based, functional connectivity counterparts. Most recent developments in indices of sediment connectivity deal, to some extent, with different styles of anthropogenic and hydro-meteorological forcings and with the temporal variability of sediment connectivity, by incorporating additional variables and parameters in existing indices. We believe that, in order to use structural connectivity as explanatory or predictive tool, indices need to be interpretable in relation to geomorphic processes, material properties, and forcing styles and magnitude-frequency spectra. Improvements in this direction can be made through studies shaped to constrain structural-functional correlations across a range of hydro-meteorological scenarios, for example employing field-based techniques such as particle tracking and sediment provenance analysis, as well as numerical simulations. We further consider existing indices in relation to spatial and temporal scales. The latter have immediate implications on the distinction and application between indices and models of sediment connectivity. In this context, we suggest that sediment connectivity over millennial or longer time scales should be dealt with models, as opposed to indices. This paper forms part of the activities of the EU-funded COST action “CONNECTEUR” (ES1306; http://connecteur.info). Working group 4 (on “useable indices of connectivity”) thanks CONNECTEUR for funding two workshops in Eichstaett and Tallinn during which this paper has been developed. Damià Vericat is supported by a Ramon y Cajal Fellowship (RYC-2010-06264). Authors acknowledge the support from the Economy and Knowledge Department of the Catalan Government through the Consolidated Fluvial Dynamics Research Group (2014 SGR 645), and the CERCA Programme.

Published
2018

50. High-resolution seismic imaging of debris-flow fans, alluvial valley fills and hosting bedrock geometry in Vinschgau/Val Venosta, Eastern Italian Alps

Author

Vincenzo Picotti, Francesco Brardinoni, Pier Paolo Bruno, Volkmar Mair, Stefano Maraio, Maraio, Stefano, Bruno, Pier Paolo G., Picotti, Vincenzo, Mair, Volkmar, Brardinoni, Francesco, Maraio, S., Bruno, P. P. G., Picotti, V., Mair, V., and Brardinoni, F.

Subjects
geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Bedrock, Fluvial, Geometry, 010502 geochemistry & geophysics, 01 natural sciences, Debris flow, Nappe, Tectonics, Geophysics, Tributary, Alluvium, Sedimentary rock, Geology, 0105 earth and related environmental sciences
Abstract

High-resolution active-source seismic surveys target the stratigraphic and structural configuration of the mid-Venosta Valley, which hosts two mega fans located at the confluence between the Adige River and its tributaries: the Gadria-Strimm fan and the Lasa fan. We aimed at imaging with high detail: 1) the postglacial sediment accumulation within the fans, 2) the characteristics of Adige river deposits, and 3) the stratigraphic/structural relationships among fans, alluvial deposits and top of the bedrock (i.e. Otztal- Ortles-Campo Nappe units). Alluvial and debris-flow fan environments often pose significant challenges to high-resolution seismic exploration , due to the high heterogeneity and the rugged topography of the near surface. We processed our data by integrating first-arrivals refraction tomography with Common Midpoint, and Common Reflection Surface seismic reflection techniques. All methods produced complementary results which allowed us reaching a well-constrained imaging of the internal architecture of the Quaternary sedimentary cover, as well as of the geometry of the hosting bedrock surface. Our result show that the sedimentary record investigated by our profiles is nested in a strongly asymmetrical valley geometry, suggesting that the tectonic forcing associated with the contact between Otztal- Ortles-Campo Nappe units has interacted closely with fluvial and/or glacial valley incision over the past millennia. We provide also a quantitative estimation of the overall thickness of sediment accumulation in the valley and allow to evaluate the complex postglacial sediment dynamics between the Adige River and the Gadria and Lasa fans, with the Gadria system playing a dominant role in terms of sediment supply.

Published
2018

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