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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.

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'

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.

Steep mountain channels are intrinsically transitional systems, in that they connect water, sediment, and wood fluxes from hillslopes, chiefly dominated by colluvial processes, to highorder streams, in which fluvial transport prevails. Owing to the variety of colluvial–alluvial interactions, the transient forcing of tectonic activity and Pleistocene glaciations, in conjunction with ongoing atmospheric temperature rise and increasing anthropogenic impacts, mountain channels exhibit complex, largely unknown hydro-geomorphic dynamics. An improved understanding of these systems is needed for addressing fundamental scientific issues such as hillslope-channel coupling mechanisms and landscape evolution, as much as for solving more practical problems, including sediment management and the prevention/mitigation of flood- and debris flowinduced disasters. This special issue encompasses a number of studies addressing the morphodynamics of steep mountain channels while focusing on different geomorphic processes and spatial/temporal scales, and across a variety of physiographic settings, all testifying to the dynamic and diverse nature of such channel typologies. The wide range of techniques presented here, exemplifies how direct and surrogate bedload measurements, flume experiments, sedimentology and dendrochronology can all help shed some new light on the hydrogeomorphic functioning of steep channels.

_, Geomorphology for Society, Conference proceedings

Climate change, human activity and other environmental disturbances can affect Earth surface systems via alteration of vegetation cover, hydrologic regime, permafrost distribution, and glacier fluctuations. For example, Pleistocene temperature drop had profound climatic and geomorphic influences worldwide, including abrupt glacial advance in vast terrestrial areas that have both sculpted the topography and deposited extensive mantles of glacigenic materials. In consideration of such legacies, formerly glaciated landscapes today can be considered at a unique stage of readjustment (recovery) with respect to the spatial organization of currently active geomorphic process domains (Brardinoni and Hassan, 2006), and the magnitude and patterns of sediment fluxes (Church and Slaymaker, 1989; Hewitt et al., 2002;Warburton, 2007). Accordingly, both contemporary environmental changes and disturbances over the Quaternary are significantly influencing patterns of weathering, detachment, transport, and deposition of material across landscape components. It is a challenge to develop a better understanding of how such changes and disturbances interact to modulate sedimentary source-to-sink fluxes and budgets in the light of peculiar landscape sensitivities (Slaymaker et al., 2009).

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.

To characterize channel-network morphodynamics and response potential in the Gadria-Strimm basin (14.8 km^2) we conduct a concerted effort entailing: (i) high-resolution mapping of landforms, channel reaches, and sediment sources; and (ii) historical evolution of colluvial channel disturbance through sequential aerial photosets (1945-59-69-82-90-00-06-11). The mapping was carried out via stereographic inspection of aerial photographs, examination of 2.5-m gridded DTM and DSM, and extensive field work. The study area is a formerly glaciated basin characterized by peculiar landform assemblages imposed by a combination of tectonic and glacial first-order structures. The most striking feature in Strimm Creek is a structurally-controlled valley step separating an upper hanging valley, dominated by periglacial and fluvial processes, and a V-notched lower part in which lateral colluvial channels are directly connected to Strimm’s main stem. In Gadria Creek, massive kame terraces located in proximity of the headwaters provide virtually unlimited sediment supply to frequent debris-flow activity, making this sub-catchment an ideal site for monitoring, hence studying the mechanics of these processes. Preliminary results point to a high spatial variability of the colluvial channel network, in which sub-sectors have remained consistently active during the study period while others have become progressively dormant with notable forest re-growth. In an attempt to link sediment flux to topography and substrate type, future work will involve photogrammetric analysis across the sequential aerial photosets as well as a morphometric/geomechanical characterization of the surficial materials.

To evaluate landslide response of mountain drainage basins to forest management we examine a historical inventory in northeastern Vancouver Island. The study area is underlain by extrusive (upper Triassic Karmutsen Formation) and intrusive rocks (Jurassic Island Intrusions). The dataset, compiled via interpretation of sequential aerial photosets, helicopter traverses, and extensive fieldwork, comprises a total of 1961 sediment sources, including 798 field-measured events. Field- and photo-based data cover a time window of approximately 70 years. The effects of forest management on landslide activity are assessed in terms of landslide density, sediment production, landslide geometry, landslide magnitude-frequency relations, topographic conditions of landslide initiation and deposition, and sediment redistribution across landscape components. Results indicate that forest management alters natural landslide dynamics in many respects. Logging-related debris avalanches are typically smaller. Consequently, the magnitude-frequency relation in logged terrain occupies the small-medium magnitude spectrum (< 6000 m3), with frequencies increasing by over an order of magnitude. Lithologic effects on sediment production appear amplified, in that terrain underlain by extrusive rocks become increasingly more unstable than intrusive ones. Analysis of landslide initiation and deposition zones reveals that forest management promotes colluvial aggradation on mid and lower hillslopes and in gullies. This pattern, which accelerates sediment recharge of gully systems, has the potential of increasing the frequency of channelized debris-flows, hence cause an extended period of disturbance, before sediment dynamics recover to pre-logging conditions. The effects of forest clearing on hillslope-channel coupling are composite: in cutblocks the percentage of sediment delivered to streams is reduced by 20-60% whereas road-related landslides are associated with highestconnectivity to streams.

Basin-wide erosion rates can be determined through the analysis of in situ-produced cosmogenic nuclides based on the idea that samples taken at the outlet of a catchment are representative of the entire upstream basin. However, this is only true when a certain number of assumptions are verified. Among the most important assumptions is that denudation rates are uniform through space and time; i.e. the catchment is in cosmogenic steady-state. If this is the case, then the in-going nuclide flux through production is equal to the out-going flux through decay and erosion, and the system is in isotopic equilibrium. When this condition is not matched, the calculation of basin-wide erosion rates through cosmogenic nuclides is subject to the well-mixing conditions of the alluvial sediment in the rivers. Here, we bring a new contribution towards the understanding of sediment mixing effects on in-situ cosmogenic nuclide concentrations in alluvial sediment. We proceed by following the methodology proposed by Binnie et al. (2006), and present the results from a sediment mixing model for a small ( 42 km2) catchment in the Alps. The model results show the importance of the sampling location and of the catchment’s size to have reliable erosion rates. However, the models also highlight the importance of knowing the sediment transfer mechanisms and the processes magnitude. When the transport of sediment mainly occurs through soil creep and shallow landslides, high concentration material is supplied into the fluvial system, increasing the 10Be concentration in the alluvial sediment. Likewise, the high-frequency of mass-wasting processes or the occurrence of sporadic but large-magnitude events, allow the supply of low-concentration sediment that result in a lower cosmogenic nuclide signal in the channels. A strong bias arises for the calculation of basin-wide erosion rates if mass-wasting processes dominate the mechanisms of sediment transfer in the catchment. In this situation the use of cosmogenic nuclides signal results in an over- or underestimation of the erosion rates. Therefore, our results suggest that when using cosmogenic nuclides, the achievement of mixing conditions in alluvial sediment is of primary importance for the correct estimation of the erosion rates and that this latter has to be accurately interpreted when the mixing conditions are unknown or not achieved.

Debris flows are the most efficient processes of sediment transfer from slope base to alluvial fan terminus in mountain drainage basins. To advance current understanding of debris-flow sediment dynamics at the regional scale we analyze historical debris-flow events in 82 basins of the Alto Adige Province, north-eastern Italy. By combining historical information on event-based debris-flow volumetric deposition and high-resolution (LiDARderived) digital topography we (i) identify seasonal trends in debris-flow activity; (ii) characterize the principal topographic conditions at which debris-flow initiation, transportation, and deposition occur; (iii) detail debris-flow sediment transfer at the basin and the regional scales; and (iv) identify lithologic dependences on debris-flow activity. For the first time, we show that basin-wide specific sediment yield describes a negative scaling relation with basin area, which in turn, is modulated by dominant bedrock geology and chiefly by the abundance of glacial and paraglacial surficial materials.

Debris flows are efficient processes of sediment transfer from slope base to alluvial fans in mountain drainage basins. To advance current understanding of debris-flow sediment dynamics at the regional scale we analyze a historical (1998-2009) database of debris flows in 82 selected basins of the Alto Adige Province, north-eastern Italy. By combining historical information on event-based debris-flow volumetric deposition, high-resolution (LiDAR-derived) digital topography, and mapping of Quaternary sediment stores we are able to (i) characterize the principal topographic conditions at which debris-flow initiation, transportation, and deposition operate; (ii) detail debris-flow sedimentary signatures across spatial scales; and (iii) link debris-flow sediment flux to morphometry, lithologic variability, and sediment availability. We show that basin-wide specific yield obeys a negative scaling relation with basin area, which in turn is strongly controlled by dominant bedrock geology and abundance of Quaternary deposits. When the event-based sediment flux is subsumed across spatial scales, a more complex sedimentary signature is apparent, regardless of sediment availability. We hypothesize that this signature is characteristic of most debris-flow dominated settings.

Debris flows are one of the most relevant natural hazards in mountain regions. A combination of structural (e.g. check-dams) and non structural (e.g. warning systems) measures is needed in most cases to reduce debris flow risks, and both benefit from experimental data on debris-flow characteristics. A new experimental site is being equipped in the Autonomous Province of Bolzano (Italy) for both monitoring purposes and testing warning systems. The study site (Gadria basin) is a small channel subjected to frequent debris flows. The overall system includes the following components: 4 rain gauges located at different elevations, 5 radar sensors and 5 geophones, and 3 video cameras and flash lights to record the propagation and the deposition of the debris flow. Transmission of data and alerts from the instruments will use radio technology because GSM coverage is not available in the basin.

Landslides exert prominent controls on the morphology of mountain drainage basins and drive the overall sediment flux across landscape components. In this context, historical landslide inventories are critical for quantifying landslide sediment dynamics through time and assessing relevant contributions to regional sediment budgets. We present an historical inventory that combines the mapping of deep-seated gravitational slope deformations (DSGSD) and shallow landslides in Val di Sole (707 km2), eastern Central Alps, Italy. The study area was selected for two reasons: (i) the composite geological setting including intrusive, metamorphic, and sedimentary formations, which provides the opportunity to evaluate lithological effects on landslide sediment transfer; and (ii) the homogeneous distribution of forest cover, which warrants higher reliability of landslide identification through time. In so doing we avoid areas dominated by large rock walls and sedimentary linkages (e.g., unvegetated talus slopes and screes), typically associated to a chronic flux of colluvial sediment. In these conditions, owing to the subtle contrast between parent material and freshly eroded debris, the identification of fresh landslide scars in sequential photosets is difficult and unreliable. For the same reason, evaluation of the visibility time window for clusters of landslides would become highly uncertain. Data collection involved interpretation of seven sequential photosets (1959, 1969, 1973, 1983, 1996, 2000, 2006) and LiDAR-derived hillshade rasters in conjunction with field measurements. Fieldwork served to measure landslide depths and obtain a volumetric transformation factor for remotely-sensed landslide areas. Inspection of LiDAR hillshades allowed to identify and delineate the perimeter of large slope deformations, otherwise masked by a number of environmental conditions during aerial photo interpretation (e.g., forest cover, shadow, and snow). In the compilation of the inventory, the use of high-resolution hillshades and aerial photos did not prove to be mutually exclusive. If on hand, the former method reduces uncertainty in the identification and delineation of landslide features, on the other it is too expensive to be repeated in time and obtain a multi-temporal dataset. Aerial photographs have limitations in terms of landslide identification, but they are relatively affordable, they have good coverage for large parts of the country since 1950s, and allow to analyse landslide sediment dynamics through time. Results show that the two methodologies should be employed in an integrated approach. We identify a total of 220 DSGSD and 3369 shallow rapid failures that cover an area of 174 km2 and 92 km2 respectively. The corresponding sediment flux exhibits lithologic and topographic controls. Metamorphic, sedimentary, and intrusive terrain are associated with progressively lower rates of sediment production and subsequent delivery to the drainage network. In this context, local confounding modulated by the presence of thick glacigenic deposits is common. Interestingly, lithologies with high density of DSGSD events exhibit higher rates of shallow-rapid failures. This finding suggests that DSGSD events by favouring/preparing the occurrence of shallow rapid failures may control, in an indirect way, landslide sediment flux at the regional scale.

Landscape evolution in mountainous catchments is the result of multiple factors acting at different scales in time and space. The main components affecting basin morphologies are: uplift, glacial cycles, erosion (long timescale), mass movements and cycles of freeze-thaw (short timescale). In this study, we quantify the rates of sediment production and transfer from an alpine catchment in which debris flows are a dominant geomorphic agent. We use cosmogenic nuclides to determine the connectivity between source areas and sinks and to estimate the timescale of sediment production and the fluxes of sediment through the basin. The Zielbach basin consists of a ca. 30 km2-large central basin where cascade and step-pool channels have eroded into the highly fractured and foliated metamorphic bedrock, and a ca. 10 km2-large eastern tributary basin where a network of debris flow channels are perched on a deep-seated sackung. Whereas the central basin shows a poor connectivity between hillslopes and the channel network, the debris flow channels of the eastern tributary basin are closely connected with the bordering hillslopes. In the central basin, the geometry of the channel network is strongly affected by the litho-tectonic fabric as channels parallel the major faults and foliations. In the headwaters, rock glaciers and rock fall deposits tens of meters thick form transverse topographic ridges which retain the sediment in a semi-closed sedimentary traps. Moreover field work and GIS analysis reveal a strong relationship between structural setting and sediments production in which sediment production is high in weakened shear and fault zones. The eastern tributary basin has highly fractured bedrock, partially related to ice retreat after the LGM age. The whole catchment is characterize by a high production of sediments related both to tectonic structure present in the area and to the steep slopes left by the glacial retreat. The geomorphology shows a clear difference between the main basin and the debris flow tributary: the first one is composed by several lateral valley in which sediment can be stored before reaching the channel network, while the tributary is characterize by a long steep slope where the sediments produced can be easily moved down to the fan. 10Be based denudation rates confirm these differences: rates are nearly constant at between 0.3-0.6 mm/yr in the decoupled hillslope-channel segments. This central tributary system of the Zielbach basin can thus be understood as a supply-limited basin with a poor connectivity between sediment sources and drainage network. In contrast, basin averaged denudation rates are high and locally exceed 2.7 mm/yr in the eastern debris flow basin revealing a high connectivity between hillslopes and channel network. Mass balance calculations reveal that individual debris flows contribute up to 90% of the sediment budget of the entire Zielbach basin. These results reveal the importance of stochastic sediment transfer from a high-connectivity tributary on the sediment budget of an entire drainage basin.

In coastal British Columbia, Canada, the glacial palimpsest profoundly affects the geomorphic structure of mountain drainage basins. In this context, by combining remotely sensed, field- and GIS-based data, we examine the scaling behavior of bankfull width and depth with contributing area in a process-based framework. We propose a novel approach that, by detailing interactions between colluvial and fluvial processes, provides new insights on the geomorphic functioning of mountain channels. This approach evaluates the controls exerted by a parsimonious set of governing factors on channel size. Results indicate that systematic deviations from simple power-law trends in bankfull width and depth are common. Deviations are modulated by interactions between the inherited glacial and paraglacial topography (imposed slope), coarse grain-size fraction, and chiefly the rate of colluvial sediment delivery to streams. Cumulatively, departures produce distal cross-sections that are typically narrower and shallower than expected. These outcomes, while reinforcing the notion that mountain drainage basins in formerly glaciated systems are out of balance with current environmental conditions, show that cross-sectional scaling relations are useful metrics for understanding colluvial-alluvial interactions.

Mountain drainage basins are complex systems due to the variety of active geomorphic processes,their interactions at different spatial/temporal scales, and the history of the landscape in terms of climate and tectonic activity. geomorphic coupling. These systems encompass hillslopes dominated by diffusive surface erosion and/or landsliding, steep confined channels dominated by debris flows, and purely alluvial channels flowing along major valley floors where fluvial transport prevails. In this context, the overall process of sediment transfer across landscape components and the associated disturbance-cascade are poorly understood, including the relative importance of one geomorphic process over the others at the watershed scale. In places where hillslopes and channels are well-connected, transport processes overlap, hence strongly interact via geomorphic coupling. The term coupling is used in geomorphology (e.g.,Brunsden and Thornes, 1979; Caine and Swanson, 1989) to indicate the degree of connectivity between hillslope and fluvial processes. Coupled systems exhibit direct colluvial-alluvial interaction, as opposed to decoupled (or buffered) systems, where colluvial sediment inputs do not reach the channel network. Evaluation of degree of coupling is critical to drainage basin sediment dynamics as it controls (i) sediment and process-disturbance cascades, and (ii) in what proportion hillslope denudation rate contributes to drainage basin sediment storage and fluvial sediment yield respectively (e.g., Roberts and Church, 1986; Reid and Dunne, 1996). In geomorphology, the importance of coupling between channels and adjacent hillslopes has been long acknowledged (e.g., Korup, 2005; Fryirs et al., 2007). However, relatively little work has attempted to assess its role in a systematic way. Partly because only very few empirical studies (both field-based and remotely-sensed) have tried to combine hillslopes and channelized landscape components (Benda et al., 1998). In this lecture, we will (i) evaluate how hillslope-channel connectivity can affect channel-reach morphology, channel geometry, and sediment transport potential through published examples and unpublished datasets; (ii) propose future research needs on the topic.

We examine basin-wide colluvial sediment dynamics in the Tsitika and Eve Rivers(about 600 km2), coastal British Columbia, Canada. The colluvial sediment cascade is documented by classifying landslide types, characterizing the dominant sediment sources, and identifying preferential sites of colluvial delivery across the landscape. The study is based on the compilation and analysis of a 70-year landslide inventory. This analysis reveals that open-slope landslides delivering material to seasonal or perennial channels and fluvial terraces are the dominant source-to-sink pathways. This finding indicates high instability of the headwaters drainage network and its ongoing adjustment after generalized sediment recharge occurred in the Last Glacial Maximum (LGM). To quantify interactions between colluvial and fluvial processes the landscape has been subdivided into geomorphic domains, which include planar slopes, unchannelled valleys, erosional (source) and depositional (sink) colluvial channels, as well as fluvial channels. In the study period, landslide activity across landscape components has generated net sediment degradation on planar slopes and source colluvial channels, whereas unchannelled valleys, sink colluvial channels and fluvially-dominated channels have been accumulating material. The newly-developed scaling relation of the landslide sediment yield appears to be controlled by the spatial organization of relict glacial structures. It follows that landslide yield is highest in unchannelled topography, decreases at the scale of channel initiation(drainage area (Ad) about 0.002 km2), and remains constant for scales where source colluvial and hanging fluvial domains overlap (0.002 < Ad< 0.06). Landslide sediment injections start declining consistently beyond areas larger than 0.6 km2 (the scale of relict trough initiation), where fluvial environments are still partially connected to adjacent hillslopes. Cumulative daily yield indicates that landslide sediment redistribution across the landscape is limited to relatively small drainage areas;specifically, 90% of the colluvial load is released at scales smaller than about 0.6 km2. Evaluation of the studied landslide yield trend in conjunction with British Columbia fluvial sediment yield allows us to identify landscape scales of sediment aggradation and degradation, hence to infer preferential scales of contemporary sediment storage.

We examine basin-wide colluvial sediment dynamics through the compilation of a 70-year landslide inventory in mountain environments of coastal British Columbia. In particular, we document the colluvial sediment cascade by characterizing the dominant sediment sources, and by identifying preferential sites of colluvial delivery and storage across landscape scales. Results reveal that open-slope landslides evacuating material to ephemeral or permanent streams and fluvial terraces are the preferential source-to-sink pathways. This pattern suggests high instability of the headmost channel network and its ongoing re-organization after generalized sediment recharge occurred during the last glacial maximum. In the study period, the colluvial sediment budget calculated across geomorphic process domains indicates net volume loss on planar slopes and source colluvial channels, whereas unchannelled valleys, sink colluvial channels and fluvially-dominated channels have been aggrading. In this context, we propose a novel approach to represent colluvial sediment yield as a function of drainage area. This scaling relation appears to be controlled by the spatial organization of geomorphic process domains, as imposed by the morphometry of the glacial palimpsest. It follows that colluvial yield is highest in unchannelled topography, decreases at the scale of channel initiation, and remains constant for drainage areas where source colluvial and hanging fluvial domains overlap. Colluvial sediment injections start declining consistently beyond areas larger than 0.6 km2, where fluvial environments are still partially coupled. Evaluation of the colluvial scaling trend in conjunction with British Columbia fluvial sediment yield, allows us to identify landscape scales of sediment aggradation and degradation, hence to infer preferential scales of contemporary sediment storage.

Landslide magnitude-frequency (LMF) and yield-area relations are examined for evaluating landslide-driven sediment dynamics in the Tsitika and Eve Rivers (612 km{2}), British Columbia. Research methods couple field work and air photo interpretation (API) in a GIS environment. API covers a seventy year time window. Results show that the long history of glacial erosion and the more recent forest management affect contemporary landslide activity in many respects. First, the nature and distribution of Quaternary-derived surficial deposits confounds primary lithologic effects; therefore, topographies underlain by less resistant geology are not typically associated with higher rates of landsliding. Second, the stratifications of LMF by landslide and terrain attributes have allowed detecting for the first time characteristic landslide length scales dependent on (i) movement style (i.e., slide, avalanche, and flow); (ii) type of material mobilized (i.e., bedrock and debris); and (iii) land use (i.e., forest clearing). As a conclusion, landscape bio-morphometric controls override the theoretical self-organized criticality of LMF relations. Third, slope-area analysis of landslide initiation and deposition zones reveals that bedrock landslides dominate the landscape on mountain summits and ridges; these processes deliver material to colluvial channels, in which debris is temporarily stored until remobilization occurs via full-scale debris flows. In undisturbed forest, during the seventy years examined, colluvial activity across geomorphic process domains (seen as sediment reservoirs) has generated net volume accumulation in unchannelled valleys, sink colluvial, and fluvially-dominated channels; in contrast, planar slopes and gullies have been degrading. Logging operations have accentuated aggradation in gullies and in unchannelled topographies. Finally, the area-based scaling relation of landslide sediment yield appears to match the spatial organization of geomorphic process domains. In this context, the contemporary, specific fluvial sediment yield (suspended) of British Columbia exceeds the specific landslide yield for drainage areas comprised between 5 and 50 km{2}. Cumulative daily yield indicates that colluvial sediment redistribution across landscape scales is limited to relatively small drainage areas; specifically, 90% of the colluvial load is injected within contributing area of about 0.6 km{2}.

The spatial distribution of channel types in mountain drainage basins of coastal British Columbia is examined. Using field- and GIS-based data we show that the local channel slope and degree of colluvial-alluvial coupling imposed by the glacial valley morphology dictate the spatial organization of channel-reach morphology. In particular, the glacially-induced channel long profile generates characteristic sequences of channel reaches (with repetitions and inversions) that depart from the downstream succession distinctive of unglaciated mountain streams. For example, the presence of one hanging valley in the river long profile produces and separates two full successions of channel types a headmost one characterized by an ephemeral/seasonal hydrologic regime, and a downstream one, where water runoff is perennial. Exploratory scatter plots indicate that slope, shear stress, and relative roughness ensure best separation between reach types. At a confirmatory level, highest prediction of channel types is achieved by discriminant functions containing the same three variates. Success rates, depending on whether or not boulder-cascade reaches are grouped with step-pools, vary between 89% and 76%. Notwithstanding the glacially-inherited slope and the transient geomorphic dynamics of this landscape, similar to the case of unglaciated mountain streams, channel types are chiefly segregated by local slope (albeit characterized by significantly higher ranges), and to a lesser extent by shear stress and relative roughness. This outcome, while adding considerable strength to prior empirical knowledge, indicates that first-order physical conditions at which distinct channel states form are insensitive to very different landscape structures, hence histories.

In glaciated regions of British Columbia, Canada, Quaternary climate changes are responsible for profound spatial reorganization of earth surface processes. These changes have left a landscape characterized by topographic anisotropy associated with a hierarchy of glacial troughs. Currently, fluvial and hillslope processes dominate the landscape, and are slowly reshaping the glacial inherited anisotropy. The aim of our study is to examine the evolution of glaciated mountainous landscapes by analysing the structure of geomorphic process domains, channel long-profiles, downstream trends of hydraulic geometry and channel morphology. The methodological approach entailed extensive channel surveys and GIS analysis to plot area-slope transects along the main stem of drainage basins. This analysis reveals generalized process-form disequilibrium with a mismatch between topographic signatures and currently active geomorphic process domains. In debris-flow dominated channels the glacial/paraglacial signature commonly overrides that produced by contemporary debris flows. Along the axis of former ice flows, relict glacial cirques introduce a “hanging” fluvial domain at contributing areas as small as 6*10-2 km2 and produce channel long-profiles similar to those observed for rivers responding to tectonic forcing. The well-established area-slope relations with simple downstream power law relations for unglaciated environments do not apply here, although the concept of process domains appears to hold. In other words, the spatial distribution of process domains on an area-slope plot may be similar but where the topography plots on these process domains varies between landscape types. At the reach scale, these same glaciated basins display significant deviations from simple downstream variation of channel slope, width, stream power and consequently the sequencing of channel morphology. Such variations are due to local, glacially-induced influences that typically reset downstream trends. The combination of glacial and post-glacial fingerprints and the effects of ongoing earth surface processes generate a more complex landscape pattern of process domains and morphologies than typical for “equilibrium” unglaciated watersheds.

In glaciated regions of British Columbia, Canada, Quaternary climate changes are responsible for profound spatial reorganization of earth surface processes. These changes have left a landscape characterized by topographic anisotropy associated with a hierarchy of glacial troughs. Currently, fluvial and hillslope processes dominate the landscape, and are slowly reshaping the glacial inherited anisotropy. The aim of our study is to examine the evolution of glaciated mountainous landscapes by analysing the structure of geomorphic process domains, channel long-profiles, downstream trends of hydraulic geometry and channel morphology. The methodological approach entailed extensive channel surveys and GIS analysis to plot area-slope transects along the main stem of drainage basins. This analysis reveals generalized process-form disequilibrium with a mismatch between topographic signatures and currently active geomorphic process domains. In debris-flow dominated channels the glacial/paraglacial signature commonly overrides that produced by contemporary debris flows. Along the axis of former ice flows, relict glacial cirques introduce a “hanging” fluvial domain at contributing areas as small as 6*10-2 km2 and produce channel long-profiles similar to those observed for rivers responding to tectonic forcing. The well-established area-slope relations with simple downstream power law relations for unglaciated environments do not apply here, although the concept of process domains appears to hold. In other words, the spatial distribution of process domains on an area-slope plot may be similar but where the topography plots on these process domains varies between landscape types. At the reach scale, these same glaciated basins display significant deviations from simple downstream variation of channel slope, width, stream power and consequently the sequencing of channel morphology. Such variations are due to local, glacially-induced influences that typically reset downstream trends. The combination of glacial and post-glacial fingerprints and the effects of ongoing earth surface processes generate a more complex landscape pattern of process domains and morphologies than typical for “equilibrium” unglaciated watersheds.

We present a new rock glacier inventory compiled for the Orobic Alps (2000 sqkm) and the Livigno Valley (270 sqkm), Lombardy Region, Italy. This effort is part of a larger ongoing project that aims at building a region-wide database of periglacial landforms. The two study areas represent the extremes, in terms of hydro-climatic and physiographic characteristics, within the spectrum of alpine terrain variability in Lombardy. The inventory of the two study areas has been conducted by combining a number of remotely-sensed images with field traverses. Specifically, the interpretation of high-resolution (0,5 x 0,5 m) digital aerial photos flown in 2000, 2003 and 2007 in conjunction with a 2-m DSM (Digital Surface Model), allowed identifying and mapping 416 and 108 rock glaciers in the Orobic Alps and in the Livigno Valley respectively. Measurements and photographs taken during fieldwork provided critical ground control for the validation of data extracted from remotely-based analysis. Attributes for each rock glacier include type (talus-lobate, talus-tongue shaped, debris-lobate, debristongue shaped, and protalus rampart), activity (active/inactive, or relict), minimum and maximum elevation, aspect, slope, geographic location, area, and dominant lithology. Preliminary results sh ow that in both study areas rock glaciers are quite uniformly distributed, with lower spatial densities in the most heavily glacierized areas. This pattern seems to reflect the geomorphological classification between glacial and periglacial environments. In the Orobic Alps, 388 (93%) rock glaciers were classified as relict while only 23 (21%) in Livigno Valley with 75 (89%) active or inactive. The most common rock glacier type in both areas are protalus ramparts (59% in the Orobic Alps and 36% in the Livigno Valley) followed by talus lobate rock glaciers (35% in the former and 32% in the latter). The active/inactive rock glacier’s minimum elevation, often considered discontinuous permafrost’s lower limit, is set a 2747 m a.s.l. in the Livigno Valley and 2386 m a.s.l. in the Orobic Alps. In both study areas, rock glaciers sit at similar slopes (chiefly around 20-25_), face predominantly north sectors, and are composed by metamorphic debris, in agreement with local dominant lithologies. The identification and classification of rock glaciers in Lombardy will form the basis to draft a preliminary regionwide mapping of discontinuous permafrost potential; hence, test and refine available physically-based models of permafrost spatial distribution.

We present a new rock glacier inventory compiled for the Orobic Alps (2000 sqkm) and the Livigno Valley (270 sqkm), Lombardy Region, Italy. This effort is part of a larger ongoing project that aims at building a region-wide database of periglacial landforms. The two study areas represent the extremes, in terms of hydro-climatic and physiographic characteristics, within the spectrum of alpine terrain variability in Lombardy. The inventory of the two study areas has been conducted by combining a number of remotely-sensed images with field traverses. Specifically, the interpretation of high-resolution (0,5 x 0,5 m) digital aerial photos flown in 2000, 2003 and 2007 in conjunction with a 2-m DSM (Digital Surface Model), allowed identifying and mapping 416 and 108 rock glaciers in the Orobic Alps and in the Livigno Valley respectively. Measurements and photographs taken during fieldwork provided critical ground control for the validation of data extracted from remotely-based analysis. Attributes for each rock glacier include type (talus-lobate, talus-tongue shaped, debris-lobate, debristongue shaped, and protalus rampart), activity (active/inactive, or relict), minimum and maximum elevation, aspect, slope, geographic location, area, and dominant lithology. Preliminary results sh ow that in both study areas rock glaciers are quite uniformly distributed, with lower spatial densities in the most heavily glacierized areas. This pattern seems to reflect the geomorphological classification between glacial and periglacial environments. In the Orobic Alps, 388 (93%) rock glaciers were classified as relict while only 23 (21%) in Livigno Valley with 75 (89%) active or inactive. The most common rock glacier type in both areas are protalus ramparts (59% in the Orobic Alps and 36% in the Livigno Valley) followed by talus lobate rock glaciers (35% in the former and 32% in the latter). The active/inactive rock glacier’s minimum elevation, often considered discontinuous permafrost’s lower limit, is set a 2747 m a.s.l. in the Livigno Valley and 2386 m a.s.l. in the Orobic Alps. In both study areas, rock glaciers sit at similar slopes (chiefly around 20-25_), face predominantly north sectors, and are composed by metamorphic debris, in agreement with local dominant lithologies. The identification and classification of rock glaciers in Lombardy will form the basis to draft a preliminary regionwide mapping of discontinuous permafrost potential; hence, test and refine available physically-based models of permafrost spatial distribution.

In glaciated British Columbia, Canada, Quaternary climate changes are responsible for profound spatial reorganization of earth surface processes. These changes have left a landscape characterized by topographic anisotropy associated with a hierarchy of glacial troughs. The evolution of formerly glaciated landscapes is examined by considering a set of scaling relations and assessing their departures from known unglaciated trends. Ultimately, the magnitude of these departures should provide a measure of the state of landscape recovery (transience) from glacial disturbance. The set of scaling dependences studied includes slope-area relations, for assessing geomorphic process domains; landslide magnitude-frequency (LMF) and yield-area relations, for evaluating landslide-driven sediment dynamics; and the spatial organization of channel-reach morphology. In addition, along channel long-profiles the scaling between drainage area and channel cross-sectional variates (downstream hydraulic geometry), coarse grain-size fraction, and stream power indices are examined. The methodological approach couples extensive field surveys, GIS-based topographic analysis, air photo interpretation, and multivariate statistical analysis. Slope-area analysis reveals generalized process-form disequilibrium with a mismatch between topographic signatures and currently active geomorphic process domains. At the landscape scale of "source" colluvial channels, the glacial/paraglacial signature commonly overrides that produced by contemporary debris flows. Along the axis of former ice flows, relict glacial cirques introduce a "hanging" fluvial domain at contributing areas as small as 8*10⁻² km² and produce complex channel long-profiles similar to those observed for rivers responding to tectonic forcing. The concept of process domains appears to hold; however, some major glacially-forced modifications in the alluvial-colluvial transition are observed and the definition of a depositional colluvial sub-domain is proposed. Direct spatial scale linkages and generalized departure from unglaciated scaling relations are observed at all levels of investigation. Glacial macro-forms, by imposing local channel gradient and degree of colluvial-alluvial coupling, dictate the spatial distribution of process domains, which in turn affect LMF relations, landslide yield, channel-reach morphology, downstream hydraulic geometry, and stream power. The combination of glacial and post-glacial fingerprints and the effects of ongoing earth surface processes generate a complex landscape whose glacial signatures may persist until the onset of the next ice age.

Episodes of climate change are responsible for profound reorganization of rates and spatial distributions of earth surface processes. In glaciated British Columbia the series of climate changes that occurred during the Quaternary have left a landscape characterized by a peculiar hierarchy of topographic anisotropies. Currently, fluvial and hillslope processes dominate the landscape, and are slowly reshaping these anisotropies. By means of extensive channel surveys, air photo interpretation, and GIS analysis we extracted slope-area transects along the main stem of drainage basins - area ranging between 1 km2 and 50 km2 - located in three different physiographic regions of British Columbia. Results display generalized process-form disequilibrium, where topographic signatures do not match with currently active geomorphic process domains. The landscape has not recovered yet from past glacial perturbations, accordingly, the combination of glacial legacies and the effects of ongoing earth surface processes generate a more complex geomorphic picture than that described elsewhere for unglaciated mountains. This emphasizes the importance of climatic and geomorphic history in interpreting contemporary landscape dynamics.

Magnitude-frequency analysis is used here as a statistical method to quantify the erosion produced by rapid shallow failures in a glaciated basin of coastal British Columbia. Coupling air photo and ground-derived data we prove that the deviation from power-law distribution observed for small magnitude is an artefact of detection deficiencies. However, the total distribution shows to be not sensitive to the occurrence of small mass failures and total erosion remains well represented in the API-derived data. Our dataset also denotes a real deviation from simple scaling at much higher magnitudes, the cause of which is currently under investigation.

In the Pacific Northwest landslide inventories are routinely compiled by means of aerial photo interpretation. When examining photo pairs the forest canopy, notably in old-growth forest, hides a population of "not visible" landslides. The present study attempts to estimate how important is the contribution of landslides not detectable from aerial photographs, to the global mass of sediment production from mass failures on forested terrain of the Capilano basin. To achieve this, aerial photo interpretation has been coupled with intensive fieldwork for identification and measurement of all landslides. In order to minimise bias in the comparison and integration of field-collected and air photo-collected data it was decided to define a 30-year time window. Incidentally, it has been possible to prove how landslide scars that appear on a single photo set would date further back than 30 years. Results show that "not visible" landslides can represent up to 85 percent of the total number of failures and can account for up to 30 percent the total volume of debris mobilised. Rates of sediment production differ greatly (one order of magnitude) between two sub-basins of the study area, suggesting that such figures should be generalised with care within a physiographic region. The difference in denudation rate is explained qualitatively by GISbased analysis of slope frequency distributions, drainage density and spatial distribution of surficial materials. Fieldwork has demonstrated that gully-related failures have a greater importance than one could expect from air photo interpretation. ANOVA and nonparametric tests indicate that careful logging in East Cap Creek has produced no detectable effects on mass wasting. Similarly, Sisters Creek, where timber harvesting stopped about 20 years before the start of our 30-year time window, has apparently recovered from the signs of past extensive logging. The existence of "not visible" events affected in a minor way conclusions about the impact of logging on slope stability in terms of land use (management) effects. It had a major impact on the nature of landslide magnitude-frequency relations and, finally is demonstrated to have implications for British Columbia Terrain Stability Classification from the terrain sensitivity point of view.

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.

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.

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.

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.

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.

We reconstruct the post-Last Glacial Maximum (LGM) evolution of the upper Adige River floodplain, Eastern Italian Alps. In particular, we are interested in constraining the time scales associated with fan building and understanding how the relevant sediment supply at tributary confluences has interacted with the Adige River to form the present landscape configuration. By combining high-resolution seismic imaging with drillhole data and radiocarbon dating, we show (i) that ~80% of the valley fill was deposited in post-LGM times, (ii) that sediment evacuation from tributaries began with local deglaciation at the end of the Younger Dryas; and (iii) that tributary basin aspect and size, by controlling the local pattern of deglaciation, may have delayed fan building by up to two millennia. Debris-flow sediment supply from the Gadria-Strimm system drove the evolution of this valley segment between 12 and 6.25 k.y. B.P., first deflecting, then damming the course of the Adige River, forming a lake, and affecting the shape and size of the neighboring fans. Our data show an anisotropic development of the Gadria fan, with growth focused on the central and eastern portion of the fan between 10 and 8.5 k.y. B.P., followed by gradual lateral shifting toward west for about the next two millennia. The estimated sediment yield associated with the fan formation describes a debris flow-driven paraglacial sedimentary wave that conforms to the conceptual model originally proposed by Church and Ryder (1972), but never tested before in upland basins with empirical data. The wave lasted for ~4 k.y. and around 9 k.y. B.P. peaked at ~390,000 m3yr-1. At the valley profile scale, results suggest that similar fans functioned as effective sediment traps, which prevented, and still limit, fluvial reworking and valley floor incision. We argue that these geomorphic barriers, which have enhanced fragmentation of the valley long profile, with knickpoints located at major tributary fans, have delayed postglacial landscape recovery until today. © 2018 Geological Society of America.

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 existing 10Be 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 Lobben oscillation. Four of the five rock avalanches dated in Val Viola cluster within the Early Holocene, in correspondence of an atmospheric warming phase. By contrast, the timing of the main Val Viola rock avalanche, 7.7 ± 0.3 ka during the Holocene Thermal Optimum, suggests a possible causal linkage to permafrost degradation. Overall, Schmidt-hammer proved to be an effective, inexpensive and versatile tool for improving the spatial resolution of Val Viola post-LGM landscape history, starting from existing numerical age constrains.

Rock avalanches are large flow-like movements of fragmented rock that can cause extensive and rapid topographic changes, for which very few quantitative data are available. This paper analyses the geomorphological and hydrological impact of the 3 million m 3 Thurwieser rock avalanche (2004, Italian Central Alps) by using Terrestrial Laser Scanner, airborne Lidar and GNSS data collected from 2005 to 2014. Sediment yield with respect to the normal valley regime, the dynamic and mass balance of affected glaciers, and the reorganization of superficial and groundwater flow networks are quantified. In the middle portion of the avalanche deposit, a natural sediment trap collected sediments from a new stream channel developed along the upper portion of the deposit and from a lateral drainage basin. This made possible to assess the 10-year impact of the rock avalanche on the sediment yield, which increased from about 120 to about 400 t km − 2 ·a − 1 . The rock avalanche partially covered a glacier with a shallow debris layer that acted as a thermal insulator, limiting ice ablation and producing a 10-m high scarp between the free surface of the glacier and the debris-covered portion. A reduction of 75% of ice ablation was observed due to thermal insulation. The rock avalanche filled a tributary valley, splitting the original drainage basin in two. Under ordinary flows, seepage occurs within the avalanche deposit along the old valley axis. During high flow conditions, a new stream channel is activated along the middle and lower margin of the deposit, which has produced a new alluvial fan on the main valley floor. The fan evolution is described up to the present volume of about 2000 m 3 .

We examine preliminary data from a landslide inventory that combines the mapping of landslides and deep-seated gravitational slope deformations (DSGSDs) in Val di Sole, eastern Central Alps, Italy. Landslide identification and classification was conducted via interpretation of sequential airphotos (API), LiDAR shaded-relief rasters. Landslide geometries were measured in the field for a sample of events. Seeking to evaluate landslide-driven sediment flux, we consider landslides as sediment sources and we classify them into rapid, full-mobility failures and slow, partial-mobility ones. The corresponding sediment flux, solely associated with rapid failures, exhibits clear lithologic controls, with metamorphic rocks displaying markedly higher landslide activity. DSGSDs occur exclusively in metamorphic terrain and landslides tend to cluster around them. Accordingly, these large-scale slope deformations could play a prominent role in modulating the contemporary landslide sediment flux. In the compilation of the inventory, the use of LiDAR and airphotos did not prove to be mutually exclusive. We recommend the two methodologies be employed in an integrated framework. © Springer-Verlag Berlin Heidelberg 2013.