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This research was funded by the European Space Agency Permafrost-CCI project (grant number 4000123681/18/I-NB). Rock glaciers are landforms related to permafrost creep that are sensitive to climate variability and change. Their spatial distribution and kinematic behaviour can be critical for managing water resources and geohazards in periglacial areas. Rock glaciers have been inventoried for decades worldwide, often without assessment of their kinematics. The availability of remote sensing data however makes the inclusion of kinematic information potentially feasible, but requires a common methodology in order to create homogeneous inventories. In this context, the International Permafrost Association (IPA) Action Group on rock glacier inventories and kinematics (2018-2023), with the support of the European Space Agency (ESA) Permafrost Climate Change Initiative (CCI) project, is defining standard guidelines for the inclusion of kinematic information within inventories. Here, we demonstrate the feasibility of applying common rules proposed by the Action Group in 11 regions worldwide. Spaceborne interferometric synthetic aperture radar (InSAR) was used to characterise identifiable moving areas related to rock glaciers, applying a manual and a semi-automated approach. Subsequently, these areas were used to assign kinematic information to rock glaciers in existing or newly compiled inventories. More than 5000 moving areas and more than 3600 rock glaciers were classified according to their kinematics. The method and the preliminary results were analysed. We identified drawbacks related to the intrinsic limitations of InSAR and to various applied strategies regarding the integration of non-moving rock glaciers in some investigated regions. This is the first internationally coordinated work that incorporates kinematic attributes within rock glacier inventories at a global scale. The results show the value of designing standardised inventorying procedures for periglacial geomorphology. Copyright: © 2022 Aldo Bertone et al. Publisher PDF

In mountain, clay-rich physiographic settings of the Northern Apennines, earth slides and earth flows are dominant processes of hillslope sediment transfer, which cause hazard and pose risk to lives and man-made structures. In Emilia-Romagna (E-R), information drawn from a region-wide inventory is customarily used for assessing landslide hazard potential and partly guides decision making on land management and urban planning. However, the inventory's historical (i.e., post-1954) degree of completeness is presently unknown. To address this gap, we integrate and compare the existing E-R inventory with a multi-temporal landslide mapping approach at four selected study sites of the Sillaro River basin, where we perform visual interpretation of thirteen sequential aerial photo sets in the 1954- 2020 period and conduct confirmatory fieldwork. Specific objectives include evaluating the advantages of higher resolution mapping for characterizing (i) landslide extent, geometry and activity through time; and (ii) landslide interaction with the drainage network. With reference to the E-R inventory, multi-temporal mapping allowed reducing mapping uncertainty through the identification of additional first occurrences and recurrences (up to a factor of 5), additional mapped landslide area (up to a factor of 12), and combined footprint area (up to a factor of 9). Our findings indicated that the proposed approach does not always result in mapping larger (or smaller) landslide polygons, or previously undetected landslides, but provides insights on process understanding. Therefore, an added value of this mapping approach lies in its ability to detect different styles of landsliding and define most likely scenarios of evolution at the site scale. Insights were drawn through detection of: (i) headscarp upslope migration (or revegetation); (ii) newly formed gully channels and/or revegetation on landslide depositional features; and (iii) changes at landslide terminus, which allowed identifying new sediment pulses, exact delivery targets (e.g., fan, valley floor, and stream channel), as well as induced changes in channel bed texture and geometry.

River canyons are characteristic features of transient fluvial systems responding to perturbations in base level and/or sediment supply. Investigating the dynamics of canyon formation and development is challenging due to the typically long time scales and the possible experimental confounding involved. In this context, the lower portion of the Marecchia River, with a history of gravel mining on alluvial deposits resting on highly erodible (i.e., claystones and poorly consolidated sands) bedrock, offers the opportunity to set up a natural experiment and investigate the onset of canyon incision and its subsequent stages of development across five decades (1955-1993). To these ends, we evaluate decadal geomorphic changes of 10-km valley segment of the Marecchia River between Ponte Verucchio and Rimini (Northern Italy) through analysis of Digital Elevation Models derived from the application of Structure from Motion to archival aerial imagery (i.e., 1955, 1969, 1976, 1985, 1993) and from a reference-LiDAR survey (i.e. 2009), in conjunction with analysis of planimetric changes in active channel width and lateral confinement.During the 1955-2009 period, fluvial incision led to the formation of a 6-km canyon, with average vertical incision of about 15 m (in places exceeding 25 m) and a corresponding annual knickpoint migration rate of about 100 m/yr. In volumetric terms, canyon formation and evolution has involved 6.1 106 m3 (95%) of degradation and 0.29 106 m3 of aggradation (5%), with a corresponding net volume loss of 5.8 106 m3. As a result of canyon development, the active channel has narrowed by about 80%, and channel pattern has drastically changed from braided unconfined to single-thread tightly confined one. These processes were especially important during the 1955-1993 period. Since 1993 to the present, main channel is characterized by a general stability of the active channel width with evidences of a slight recovery through mass wasting processes within it. Local disturbance associated with ongoing canyon development have propagated and are still propagating upstream, posing immediate threat to infrastructures.

In mountain drainage basins, constraining source-to-sink sediment fluxes over decadal time scales is critical for evaluating hillslope and fluvial response to ongoing climate change and holds practical implications for sediment management. To this end, we combine geomorphic change detection (GCD) (Wheaton et al., 2010) and sediment provenance analysis in the reservoirs of Gioveretto (1850 m a.s.l.), Vernago (1665 m a.s.l.) and San Valentino (1499 m a.s.l.), western South Tyrol, Italy. The reservoirs are located in the Austroalpine domain and the main outcropping lithologies consist of metamorphic rocks (e.g., metapelites and gneisses).Through GCD analysis conducted on recently acquired lake-bottom DTMs (i.e., SfM-UAV and multibeam surveys) and pre-dam (i.e., contour-based) counterparts, we have mapped the spatial distribution of erosion and deposition, and have assessed the relevant sediment yields over the last six decades. The three systems, which drain areas of 69 km2 (Vernago), 77 km2 (Gioveretto) and 163 km2 (San Valentino), exhibit varying degree of glacier extent, and have experienced a different history of lake-bottom anthropogenic disturbance. Preliminary, conservative GCD results constrain net aggradation volumes that correspond to sediment yields of 35*103 m3/yr at Gioveretto (1954-2019), and 68*103 m3/yr at San Valentino (1959-2020). In this context, the much lower figure of 6.5*103 m3/yr (1962-2021) at Vernago refers to a small portion (20%) of the lake bottom, which was spared from sediment removal during maintenance work occurred in 2001-2002.To quantify the contribution of each tributary stream to the sediment yield in each reservoir, quantitative provenance analysis was carried out on 18 sand/silt samples collected from fluvial bars of major tributaries and on the 3 reservoirs. The similarity between petrographic composition of river sediments supplied by different combinations of diverse end-member sources (e.g., parent lithologies) and the observed detrital mode of the sediments in the reservoirs was quantified using a statistical distance. Next, the relative contribution to the total sediment load from each of these tributaries was calculated by forward mixing modelling (Garzanti et al., 2012). Sediments in the study streams are dominated by quartz, feldspars, and metamorphic lithic grains. Heavy minerals include hornblende, garnet, and epidote. Results of the provenance analysis indicate that in Lakes San Valentino, Gioveretto and Vernago, the dominant contributions derive respectively from Rio Carlino (Mt. Palla Bianca – Weißkugel; 3738 m a.s.l.), Rio Plima (Mt. Cevedale – Zufallspitze; 3769 m a.s.l) and Tisentalbach (Mt. Similaun 3607 m a.s.l). This contribution is part of the SedInOut project (2019-2022), funded through the V-A Italia-Österreich Interreg Programme (European Regional Development Fund). Modern bathymetric data, processed by Cartorender Srl, are kindly made available by Alperia Srl. ReferencesGarzanti E., Resentini A., Vezzoli G., Andò S., Malusà M., and Padoan M. 2012. Forward compositional modelling of Alpine orogenic sediments. Sedimentary Geology, 280, 149-164.Wheaton J.M., Brasington J., Darby S.E., Sear D.A. 2010. Accounting for uncertainty in DEMs from repeat topographic surveys: improved sediment budgets. Earth Surface Processes and Landforms, 35, 136-156.

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. ISSN:0197-9337 ISSN:1096-9837

The dependence of rock glaciers on permafrost and thus their sensitivity to climatic parameters makes the spatial distribution of these landforms very important for hydrological and climate changes reasons. Inventories of rock glaciers have been produced for decades worldwide, often without an assessment of their kinematics; the availability of remote sensing data makes the inclusion of kinematic information potentially feasible, but the absence of a common methodology makes it challenging to create homogeneous inventories. In this context, the IPA Action Group on rock glacier inventories and kinematics (2018–2023), with the support of the ESA Permafrost_CCI project, is promoting the definition of standard guidelines for the inclusion of kinematic information within inventories. Here, we test the feasibility of applying common rules proposed by the Action Group in eleven regions worldwide. Satellite interferometry is used to characterize identifiable areas with slope movements related to rock glaciers; subsequently, these areas are used to assign kinematic information to rock glaciers in existing or newly compiled inventories. More than 5,000 slope movements and more than 3,600 rock glaciers are classified according to their kinematics. The analyzes conducted on the method and on the preliminary results show small irregularities related to the detection capacity of interferometry and to lack of rock glaciers without detectable movements in some regions investigated. This is the first internationally coordinated effort of rock glacier inventories. We demonstrate the feasibility of applying common rules to implement kinematic attributes within inventories at a global scale, despite the various regions and intensive manual effort.

In mountain environments, landslides are dominant geomorphic processes of sediment transfer and as such, they play a fundamental role in landscape evolution and sediment management at the watershed scale. While monitoring of landslide dynamics at the scale of the single slope failure provides precious site-specific information, an appraisal of landslide-driven sediment dynamics at more representative spatial scales is rarely pursued. In this context, the compilation of multi-temporal, high-resolution landslide inventory represents a challenging but critical task.In the Emilia-Romagna region (Italy), landslides cover about the 24% of the hilly and mountain areas within the Northern Apennines. Here, the most common types of landslides are earth slides and earthflows that mainly involve the terrain of clay Ligurian Units and usually are the re-activations of preexisting mass movements. Since the mid ’80, the Geological Survey of Emilia-Romagna Region (RER) has started compiling and updating a region-wide landslide inventory, which includes all movement types, as well as both active (n = 44,377) and dormant (n = 36,608) landforms. The inventory update is customarily performed in selected areas, mainly where landslides have created damages or pose risk to infrastructures, or where ad hoc land planning is needed. In this context, a systematic multi-temporal approach that could provide robust information on landslide occurrence and recurrence is missing.To address this gap, in this contribution we propose a multi-temporal inventory prototype, which includes a set of attributes aimed at characterizing landslide sediment transfer across decades. The prototype is developed in the mountain portion of the Sillaro River basin (139 km2). The basin is chiefly underlain by argillites of the Ligurian domain, where earth slide and earthflow activity is pervasive.The compilation of the multi-temporal landslide inventory is conducted through visual inspection of 10 sequential aerial photo sets (1954, 1969, 1976, 1985-88, 1996, 2000, 2006, 2008, 2011, and 2014), as well as Google Earth satellite imagery (2016 and 2018). In particular, each landslide polygon encloses the total disturbed area, which includes initiation, transport and deposition zones. Polygon planimetric changes are then recorded across sequential photosets. In this way, it is possible to record recurring landslide movements.Landslide planimetric geometry includes length, width, and area. Landslide attributes include movement type, photo year of occurrence, morphologic position at initiation (source), and sediment delivery target (sink). Subsequently, for each landslide we subdivide total disturbed area into initiation-transport and deposition polygons. For recurring landslides, we note whether the movement involved: (i) the whole landslide body or only part of it; (ii) headscarp migration; and (iii) advance of the landslide terminus. Finally, we note whether the landslide deposition zone displayed headward incision by means of gully development and/or revegetation.This work, as part of the projects BEDFLOW and BEFLOW PLUS, is partially funded by Fondazione Cassa di Risparmio in Bologna.

Anthropogenic disturbance is one of the main drivers of contemporary river adjustment. In mountain streams, information and prior work on post-disturbance recovery rates is limited, compared to lowland counterparts. The BEDFLOW initiative aims to investigate fluvial morphodynamics along the mountain portion of the Sillaro River (138 km2), Northern Apennines, to guide local strategies of sediment management at the basin scale and improve environmental quality of this fluvial system. Of particular interest is the understanding of the historical and contemporary response of the Sillaro River to gravel mining activities, which focused in the mid-to-lower portions of the river between the mid-1940s and the early 1980s. To this end, BEDFLOW adopts a multi-scale approach that integrates: (1) historical analysis of planform channel changes across the entire montane channel main stem over the past 100 years; (2) hydraulic and bed texture characterization of 14 representative reaches that encompass drainage areas comprised between 2.7 and 113 km2; and (3) flood-event scale, RFID bedload monitoring in two reaches, complemented by topo-photogrammetric surveys of the subaerial and submerged channel bed.Analysis of historical channel changes was conducted by mapping active channel width on historical topographic maps (1928) and across 11 sequential aerial photo sets (1954, 1969, 1976, 1988, 1996, 2000, 2008, 2011, 2014, 2016 and 2018), along a valley segment of about 26 kilometers (i.e., 35 homogeneous reaches). Vertical channel adjustment was assessed by comparison of long profiles extracted from 1928 and 1976 topographic maps.Preliminary results indicate that the river has experienced intense channel narrowing between 1969 and 1996. This pattern has progressively slowed down, even though narrowing continues until today. Cumulatively, reduction in active channel width has been highest in the distal most unconfined reaches, where median width has decreased from >120 m in 1954 to about 20 m in 2018, intermediate in semi-confined reaches (from 99 m to 28 m), and least in the upper confined reaches (from 30 m to 15 m). In the semi-confined and unconfined reaches, where most of the gravel mining took place, channel pattern has changed from braided to wandering and/or from wandering to single-thread. Today, after about 35 years since in-channel gravel mining became interdicted, the river still exhibits signs of incomplete recovery, as bedrock sporadically outcrops amidst mid channel bars, formerly occupied by braided plains.The two monitoring reaches, which are active since February 2020, have contrasting morphology and degree of hillslope coupling. The upper one (drainage area = 35 km2) is a riffle-pool, uncoupled reach, characterized by a fine-to-coarse gravel texture and a channel slope of 0.8 %. The lower one (50 km2) is a transitional reach with dominantly plane-bed morphology and lesser riffle-pool and step-pool stretches; it is characterized by fine gravel to boulder texture, and by a channel slope of 1.5 %. The b-axis of deployed tracer stones spans from 36 to 180 mm.The Sillaro River basin functions also as a training site for students. This work, as part of the projects BEDFLOW and BEFLOW PLUS, is partially funded by Fondazione Cassa di Risparmio in Bologna.https://site.unibo.it/bedflow/enhttps://site.unibo.it/bedflow/it

In mountain environments, landslide sediment supply is one of the main factors that can affect fluvial morphodynamics. In settings underlain by clay-rich lithologies, where earthflows are the dominant agents of hillslope sediment transfer, limited quantitative information is available on the contribution of these processes to the sediment budget. This is a critical aspect both for addressing basic scientific questions on landscape evolution, as well for tackling more applied issues on river sediment management.This study focuses on the mountain portion of the Sillaro River basin (138 km2), a fluvial system underlain by argillites and siltstones of the Ligurian domain, Northern Apennines (Italy). Here, earthflows are the most common landslide type. Through the compilation of a multi-temporal earthflow inventory (1954-2019), we aim to: (i) characterize earthflow source-to-sink sedimentary pathways, with special reference to sediment delivery to ephemeral and perennial streams; (ii) explore possible litho-topographic controls on earthflow size, frequency and recurrence; (iii) examine historical trend of earthflow activity in relation to rainfall variability and land use changes. Finally, the high and extended temporal resolution of the inventory, will offer the opportunity to test how relevant information could complement the existing inventory of the Emilia-Romagna region, for evaluating earthflow hazard and risk potential.Data collection entailed inspection of 12 sequential aerial photo sets (1954, 1969, 1976, 1988, 1996, 2000, 2006, 2008, 2011, 2014, 2016, and 2018), through which earthflows were classified and mapped in GIS environment. This remotely-based activities were complemented by confirmatory field visits on a subset of most recent events. Overall, we have mapped a total of 506 earthflows, which collectively extend over an area of 4.1 km2.Preliminary results show that earthflow size (i.e., total disturbed area) ranges from 400 m2 to 98000 m2, with frequencies peaking around 10000 m2. In terms of source-to-sink pathways, we find that earthflows chiefly tend to deliver sediment to ephemeral gully channels (61%) and perennial tributaries (25%). Whereas, 5% of the events remain on the slopes, and another 5% are buffered by roads and similar anthropogenic barriers. Only a very limited proportion of earthflows (4%) makes it directly to the Sillaro River main stem.This work, as part of the projects BEDFLOW and BEFLOW PLUS, is partially funded by Fondazione Cassa di Risparmio in Bologna.

This paper aims to evaluate sources of uncertainty and variability associated with rock glacier inventories compiled from remotely sensed imagery. To this end, we ran three mapping exercises in Kaiserbergtal, Austria. To evaluate interactions between mapping style and imagery resolution, we asked six operators to map and assess the degree of activity of all rock glaciers they could identify – first on Google Earth™ (GE) imagery and then on a set of higher‐resolution orthophotos and LiDAR‐derived images (LO) (Exercise 1). To compare the mapping attributes on a common set of rock glaciers, we asked 14 operators to delineate the outline of four designated rock glaciers (Exercise 2) and to classify the activity of 15 designated rock glaciers (Exercise 3) on LO. Results show strikingly high inter‐operator variability. Specifically, we show that the number of mapped rock glaciers on GE can vary up to a factor of 3, and that using LO lowers this figure to a factor of 2, while producing an increase in the number of mapped landforms, which become systematically smaller (Exercise 1). Examination of polygon outlines identifies highest inter‐operator variability at the transition with the rooting zone and, in polymorphic rock glaciers, on adjacent creeping lobes. Variability is higher for relict landforms (Exercise 2). Operators’ activity assessments, evaluated against an independent quantitative activity index (RGI), display reasonable agreement for active and relict landforms, whereas inactive counterparts meet least consensus and therefore are problematic (Exercise 3). We further show that this variability in mapping outcomes propagates across compound variables, and must be considered when assessing uncertainties and confidence levels of environmental evaluations that rely on rock glacier inventories, such as the lower altitudinal limit of discontinuous permafrost, or water storage potential. We call for an international effort to establish guidelines for rock glacier classification and mapping, towards more homogeneous inventories. © 2019 John Wiley & Sons, Ltd.

Rock glaciers are the best visual expression of creeping mountain permafrost. Their dynamics, which largely depend on climatic forcing, provide information about the mountain permafrost and may locally pose risk to infrastructures.The International Permafrost Association (IPA) Action Group on Rock glacier inventories and kinematics, launched in 2018, fosters the activities of a research network focused on the definition of standardized guidelines for inventorying rock glaciers, including information on rock-glacier displacement rate. The ESA Permafrost_CCI project further sustains this initiative, and proposes a standardized method to implement kinematics-based rock glacier inventories.The proposed method exploits interferometric data from spaceborne Synthetic Aperture Radar (InSAR) to derive the kinematic information of existing or newly-compiled rock glacier inventories. In particular, areas identified as slope movements within rock glacier polygons are delineated on interferograms as “moving areas”, and are assigned a velocity class. Subsequently, a specific kinematic class is assigned to each rock glacier unit according to the velocity class and extension of the relevant moving areas.This method is applied on two regions: the Western part of the Swiss Alps and the South-Western part of the South Tyrol (Italian Alps). Both are located at the same latitude, with rock glaciers in the Swiss part lying at slightly higher altitudes, and experiencing higher mean annual precipitation. Rock glacier polygons were drawn from existing inventories, the kinematic information was extracted exploiting InSAR data acquired between 2018 and 2019 from the Sentinel-1 constellation.In the Swiss and Italian parts, we inventoried 660 and 783 moving areas (1443 in total). Collectively, it was possible to assign a kinematic attribute to 913 rock glaciers, providing a more objective and quantitative activity classification (compared to the qualitative active, inactive, and relict categories). In the Swiss part, 14% of the rock glaciers are moving in the magnitude order of a meter/year or faster, 43% in the magnitude order of one to several dm/yr, 36% from one to several cm/yr, the others are with unreliable movements (7%). In the Italian part, these percentages are 1% (meter/year or faster), 42% (one to several dm/yr), 39% (one to several cm/yr) and 18% (no reliable), respectively. Preliminary analyses on the Italian part are conducted on 467 additional rock glaciers recognized as geomorphologically relict: 68% are not moving or not moving fast enough to be detected, 9% have sectors moving up to several cm/yr, and the remaining 23% of relict rock glaciers have no reliable information on movement.Preliminary results show how this approach allows to provide complementary kinematic information to the geomorphological approach, improving the knowledge on the activity status in a given time and in a given region. Since several studies have reported trends towards displacement acceleration, applying this approach over long periods will allow assessing the response of a wide selection of landforms to (warmer) climatic forcing. Furthermore, this approach is a very useful tool to help select representative rock glaciers of a region, on which to apply more accurate monitoring approaches.

River canyons are transient geomorphic systems shaped by river incision into bedrock and coupled by instability of the adjacent valley walls. Investigating the evolution of river canyons is typically challenging due to the geologic time scales involved. In this context, the Marecchia River, which hosts in its intermediate portion a 6-km canyon, developed since the early 1950’s following intense gravel mining, may be instructive. Indeed, this setting offers the opportunity to: (i) document canyon development through highly erodible pelitic rocks; and (ii) evaluate relevant upstream and downstream effects on fluvial morphodynamics. To these ends, we subdivide the 50-km stretch of the Marecchia River main stem into 22 homogeneous reaches and evaluate decadal geomorphic changes through analysis of LiDAR-derived digital elevation models (i.e., 2009 and 2019) in conjunction with planimetric changes of active channel width delineated on orthophoto-mosaics (i.e., 2009, 2012, 2014, 2017, 2019). The estimation of patterns and rates of fluvial erosion into bedrock and its geomorphic effects are essential for understanding landscape evolution and for applying sustainable sediment management plans.In terms of volumetric changes, the entire river stretch recorded a decadal degradation of 2,516,150 m3 (57%) and 1,884,700 m3 of aggradation (43%), with a corresponding net volume loss of -631,450 m3. Highest specific volumes of aggradation were observed in a homogeneous reach located in the lower part of the study segment (0.5 m3/m2), while highest values of degradation were observed in the upper reach of the canyon (-2.3 m3/m2). During the 2009-2019 period, knickpoint headward migration within the canyon has progressed for approximately 500 m, producing an average bedrock incision of about 10 m. As documented by area and volume changes, both rates of fluvial incision and canyon widening, as modulated by landslide activity and valley wall collapses, are highest in proximity of the main knickpoint and tend to decrease progressively downstream. By March 2019, when the second LiDAR survey was conducted, the main knickpoint had reached the foundations of a major check dam, which eventually collapsed two months later. Upstream of the canyon, channel reaches displayed narrowing dynamics with an alternation of degradation and aggradation processes. In terms of total volumetric changes, these reaches presented an indirect correlation with confinement, with the most confined reaches acting as sediment transfer zones. In contrast, the segment downstream of the canyon displayed widening dynamics (+ 11 m on average) together with an increase of aggradation processes. Due to the pelitic nature of the hosting bedrock, despite the high geomorphic change observed, most of the material supplied by the canyon walls gets transported in suspension, contributing very little to the estimated budget of the Marecchia River's distalmost reaches. In this way, we argue that most part of the aggradation observed in this segment was originated upstream, bypassing the canyon.

Coarse bed load transport is a crucial process in river morphodynamics, but it is difficult to monitor in mountain streams. Predicting bed load is a difficult task especially in steep step-pool streams, where the critical dimensionless shear stress is affected by local channel slope and relative submergence, and only part of the flow energy is available to entrain and transport sediments as some is dissipated in local hydraulic plunging and jumps. Here we present a new sediment transport dataset obtained from two years of field-based monitoring (2014-2015) at the Estero Morales, a high-gradient stream in the central Chilean Andes. This stream features step-pool bed geometry and a glacier-fed hydrologic regime characterized by abrupt daily fluctuations in discharge. Bed load was monitored directly using Bunte samplers and by surveying the mobility of passive integrated transponder (PIT) tags. We used the competence method to quantify the effective slope, which is the fraction of the total slope responsible for bed load transport. This accounts for only 10% of the total slope, confirming that most of the energy is dissipated on macroroughness that characterize step-pool stream. We used the displacement lengths of PIT tags to derive the statistics of flight and resting times, observing that the average length of a flight scales inversely with grain size.

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.

Digital elevation models (DEMs) built from repeated topographic surveys permit producing DEM of Difference (DoD) that enables assessment of elevation variations and estimation of volumetric changes through time. In the framework of sediment transport studies, DEM differencing enables quantitative and spatially-distributed representation of erosion and deposition within the analyzed time window, at both the channel reach and the catchment scale. In this study, two high-resolution Digital Terrain Models (DTMs) derived from airborne LiDAR data (2 m resolution) acquired in 2005 and 2011 were used to characterize the topographic variations caused by sediment erosion, transport and deposition in two adjacent mountain basins (Gadria and Strimm, Vinschgau - Venosta valley, Eastern Alps, Italy). These catchments were chosen for their contrasting morphology and because they feature different types and intensity of sediment transfer processes. A method based on fuzzy logic, which takes into account spatially variable DTMs uncertainty, was used to derive the DoD of the study area. Volumes of erosion and deposition calculated from the DoD were then compared with post-event field surveys to test the consistency of two independent estimates. Results show an overall agreement between the estimates, with differences due to the intrinsic approximations of the two approaches. The consistency of DoD with post-event estimates encourages the integration of these two methods, whose combined application may permit to overcome the intrinsic limitations of the two estimations. The comparison between 2005 and 2011 DTMs allowed to investigate the relationships between topographic changes and geomorphometric parameters expressing the role of topography on sediment erosion and deposition (i.e., slope and contributing area) and describing the morphology influenced by debris flows and fluvial processes (i.e., curvature). Erosion and deposition relations in the slope-area space display substantial differences between the Gadria and the Strimm basins. While in the former erosion and deposition clusters are reasonably well discriminated, in the latter, characterized by a complex stepped structure, we observe substantial overlapping. Erosion mostly occurred in areas that show persistency of concavity or transformation from convex and flat to concave surfaces, whereas deposition prevailingly took place on convex morphologies. Less expected correspondences between curvature and topographic changes can be explained by the variable sediment transport processes, which are often characterized by alternation of erosion and deposition between different events and even during the same event.

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.

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 16 mm 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. Copyright © 2014 John Wiley & Sons, Ltd.

Basin-wide erosion rates can be determined through the analysis of in situ-produced cosmogenic nu- clides. In transient landscapes, and particularly in mountain catchments, erosion and transport processes are often highly variable and consequently the calculated erosion rates can be biased. This can be due to sediment pulses and poor mixing of sediment in the stream channels. The mixing of alluvial sediment is one of the principle conditions that need to be verified in order to have reliable results. In this paper we perform a field-based test of the extent of sediment mixing for a w42 km2 catchment in the Alps using concentrations of river-born 10Be. We use this technique to assess the mechanisms and the spatio- temporal scales for the mixing of sediment derived from hillslopes and tributary channels. The results show that sediment provenance and transport, and mixing processes have a substantial impact on the 10Be concentrations downstream of the confluence between streams and tributary channels. We also illustrate that the extent of mixing significantly depends on: the sizes of the catchments involved, the magnitude of the sediment delivery processes, the downstream distance of a sample site after a con- fluence, and the time since the event occurred. In particular, continuous soil creep and shallow land- sliding supply high 10Be concentration material from the hillslope, congruently increasing the 10Be concentrations in the alluvial sediment. Contrariwise, a high frequency of mass-wasting processes or the occurrence of sporadic but large-magnitude events results in the supply of low-concentration sediment that lowers the cosmogenic nuclide concentration in the channels. The predominance of mass-wasting processes in a catchment can cause a strong bias in detrital cosmogenic nuclide concentrations, and therefore calculated erosion rates may be significantly over- or underestimated. Accordingly, it is important to sample as close as possible to the return-period of large-size sediment input events. This will lead to an erosion rate representative of the “mass-wasting signal” in case of generally high-frequency events, or the “background signal” when the event is sporadic. Our results suggest that a careful con- sideration of the extent of mixing of alluvial sediment is of primary importance for the correct estimation of 10Be-based erosion rates in mountain catchments, and likewise, that erosion rates have to be inter- preted cautiously when the mixing conditions are unknown or mixing has not been achieved. Basin-wide erosion rates can be determined through the analysis of in situ-produced cosmogenic nuclides. In transient landscapes, and particularly in mountain catchments, erosion and transport processes are often highly variable and consequently the calculated erosion rates can be biased. This can be due to sediment pulses and poor mixing of sediment in the stream channels. The mixing of alluvial sediment is one of the principle conditions that need to be verified in order to have reliable results. In this paper we perform a field-based test of the extent of sediment mixing for a w42 km2 catchment in the Alps using concentrations of river-born 10Be. We use this technique to assess the mechanisms and the spatiotemporal scales for the mixing of sediment derived from hillslopes and tributary channels. The results show that sediment provenance and transport, and mixing processes have a substantial impact on the 10Be concentrations downstream of the confluence between streams and tributary channels. We also illustrate that the extent of mixing significantly depends on: the sizes of the catchments involved, the magnitude of the sediment delivery processes, the downstream distance of a sample site after a confluence, and the time since the event occurred. In particular, continuous soil creep and shallow landsliding supply high 10Be concentration material from the hillslope, congruently increasing the 10Be concentrations in the alluvial sediment. Contrariwise, a high frequency of mass-wasting processes or the occurrence of sporadic but large-magnitude events results in the supply of low-concentration sediment that lowers the cosmogenic nuclide concentration in the channels. The predominance of mass-wasting processes in a catchment can cause a strong bias in detrital cosmogenic nuclide concentrations, and therefore calculated erosion rates may be significantly over- or underestimated. Accordingly, it is important to sample as close as possible to the return-period of large-size sediment input events. This will lead to an erosion rate representative of the “mass-wasting signal” in case of generally high-frequency events, or the “background signal” when the event is sporadic. Our results suggest that a careful consideration of the extent of mixing of alluvial sediment is of primary importance for the correct estimation of 10Be-based erosion rates in mountain catchments, and likewise, that erosion rates have to be interpreted cautiously when the mixing conditions are unknown or mixing has not been achieved.

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 .

Colluvial sediment dynamics are examined using a 70-year landslide inventory in formerly glaciated mountain drainage basins of coastal British Columbia, Canada. Landslide sediment transfer is documented by identifying landslide types, and by characterizing preferential sites of landslide initiation, delivery, and storage across spatial scales. Data analysis reveals that open-slope landslides delivering material to seasonal or perennial channels and fluvial terraces are the dominant mechanisms of sediment transfer. This finding suggests high instability of the low-order channel network and its ongoing re-organization (degradation) after generalized sediment recharge occurred in the last glacial maximum. In the study period, landslide activity across the landscape has generated net degradation on planar slopes and first-order colluvial channels, whereas unchannelled valleys, higher-order colluvial channels and alluvial channels have accumulated material. The scaling relation of the landslide sediment yield appears to be controlled by the spatial arrangement of the relict glacial macro-forms. Landslide yield is highest in unchannelled topography, decreases at the scale of channel initiation (Ad~0.002 km2), and remains constant for drainage areas where length scales of cirque/valley walls and hanging valley floors overlap (0.002bAdb0.06). Injections of landslide material start declining consistently beyond areas larger than 0.6 km2 (the scale of relict glacial trough initiation), where fluvial environments become increasingly disconnected from landslide inputs. Cumulative yield indicates that colluvial sediment redistribution is limited to small basins; specifically, 90% of the colluvial load is released at scales smaller than about 0.6 km2

We present a regional inventory of rock glaciers ( n = 1514) and protalus ramparts (228) for the Lombardy region, central Italian Alps. To identify and classify the landforms we inspect three sequential air-orthophoto mosaics and a 2 m-DSM, and conduct confirmatory field work. The inventory forms an empirical basis to analyze: (i) the relative contribution of hillslope (i.e., talus slopes) and glacial (i.e., moraines) sediment stores to rock glacier sediment supply; (ii) linkages between the landforms inventoried and local topographic attributes; (iii) the spatial variability of periglacial activity in relation to a parsimonious set of environmental variables (i.e., elevation, precipitation, and lithology); and (iv) the effects of the Pleistocene–Holocene climatic transition on the distribution of intact and relict landforms. This analysis reveals that the elevation of rock glacier termini can vary over 200 m as a function of slope aspect. In turn, the distribution of rock glaciers among aspect categories is controlled by the structure of the valley network that promotes NW and SE exposures. Talus rock glaciers prevail numerically over the glacier-related typology, even though the latter population appears to have increased during the Holocene. Relict and intact rock glaciers have distinct spatial patterns in that the former display, on average, a 400-m elevation drop and a less clustered distribution towards northern aspects, suggesting that they have developed in more “permafrost-prone” climatic conditions. Analyzing the study region through a 27.5 km-grid has been instrumental for showing that the rock glacier specific area and terminus elevation are: (i) positively correlated with terrain elevation; and (ii) negatively correlated with mean annual precipitation. As a consequence, in relation to Holocene generalized atmospheric temperature rise, intact rock glaciers have progressively disappeared from the wetter and milder portions of the central Italian Alps. Analysis of rock glacier occurrence across litho-tectonic sectors does not provide conclusive dependences and requires further analysis. This inventory, which represents a necessary preliminary step for modelling the spatial distribution of discontinuous permafrost at the regional scale, fills a critical geographic gap in the context of ongoing permafrost research in the European Alps (e.g., PermaNET).

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In formerly glaciated mountain settings, Pleistocene glaciations are responsible for profound spatial reorganization of the landscape structure. By imposing local channel slope and the degree of hillslope–channel connectivity, glacial macro-forms can exert first-order controls on the downstream strength and continuity of the coarse sediment cascade. To estimate quantitatively these controls we trace bedload transport for 3 years along Strimm Creek, Eastern Italian Alps. Specifically, we monitor the travel distance of 490 PIT-tagged particles (b axis: 23–229 mm; weight: 83–6525 g) at two contrasting sites: Upper Strimm Creek (US; 4 km2), which flows through a fluvially dominated hanging valley, and Lower Strimm Creek (LS; 7.5 km2), located downstream, in a relict glacial trough where it experiences periodic colluvial sediment inputs from lateral tributaries. Tracer positioning within the streambed is periodically tracked in the field with a portable antenna in order to assess progressive travel distances, as well as the extent of the channel active layer, in relation to snowmelt and rainfall-driven peak flows. Interestingly, we show that tracer virtual velocities for selected inter-survey periods are independent of tracer weight at both study sites. Cumulatively, tracers in US have travelled across distances (i.e. inner quartiles) shorter than 2 m, which correspond to over 2 orders of magnitude less than what was observed in LS. These figures translate, after calculations of tracer inter-survey virtual velocities, into estimated bedload volumes equal to about 3 m3 in US and 600 m3 in LS, with most of the transport (75 % in US, and 93 % in LS) occurring during snowmelt. A similar contrast in bedload transport rates, even without considering the additional volumes of material mobilized by mass-wasting processes in LS, testifies the extent to which the glacial imprinting can still affect contemporary sediment transfer, and thus postglacial landscape evolution, in mountain drainage basins.

This paper reviews sediment transport and ch a n n e l morphology in small, forested streams in the Pacific Northwest region of North America to assess current knowledge of ch a n n e l stability and morphology relevant to riparian management practices around small streams. Small channels are defined as ones in w h i ch morphology and hydraulics may be significantly influenced by individual clasts or wood materials in the channel. Such channels are headwater channels in close proximity to sediment sources, so they reflect a mix of hillslope and channel processes. Sediment inputs are derived directly from adjacent hillslopes and from the channel banks. Morphologically significant sediments move mainly as bed load, mainly at low intensity, and there is no standard method for measurement. The larger clastic and woody elements in the channel form persistent structures that trap significant volumes of sediment, reducing sediment transport in the short term and substantially increasing channel stability. The presence of such structures makes modeling of sediment flux in these channels – a potential substitute for measurement – difficult. Channel morphology is discussed, with some emphasis on wood related features. The problem of classifying small channels is reviewed, and it is recognized that useful classifications are purpose oriented. Reach scale and channel unit scale morphologies are categorized. A “disturbance cascade” is introduced to focus attention on sediment transfers through the slope channel system and to identify management practices that affect sediment dynamics and consequent ch a n n e l m o r p h o l o g y. Gaps in knowledge, errors, and uncertainties hav e been identified for future research.

Landslide inventories are routinely compiled by means of aerial photo interpretation (API). When examining photo pairs, the forest canopy (notably in old-growth forest) hides a population of "not visible" landslides. In the present study, we attempt 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, coastal British Columbia. API was coupled with intensive fieldwork for identification and measurement of all landslides. A 30-year framework was adopted. We show that "not visible" landslides can represent up to 85% of the total number of failures and account for 30% of the volume of debris mobilised. Such percentages display high sub-basin variability with rates of sediment production varying by one order of magnitude between two sub-basins of the study area. This is explained qualitatively by GIS-based analysis of slope frequency distributions, drainage density, and spatial distribution of surficial materials. Such observations find further support in the definitions of transport-limited and supply-limited basins. As a practical consideration to land managers, we envisage that supplementary fieldwork for landslide identification is mandatory in transport-limited systems only. Fieldwork has demonstrated that gully-related failures have a greater importance than one could expect from API. © 2002 Elsevier Science B.V. All rights reserved.

The variability of glacier response to atmospheric temperature rise in different topo-climatic settings is still a matter of debate. To address this question in the Central Italian Alps, we compile a post-LIA (Little Ice Age) multitemporal glacier inventory (1860–1954–1990–2003–2007) along a latitudinal transect that originates north of the continental divide in the Livigno Mountains and extends south through the Disgrazia and Orobie ranges, encompassing continental-to-maritime climatic settings. In these sub-regions, we examine the area change of 111 glaciers. Overall, the total glacierized area has declined from 34.1 to 10.1 km2, with a substantial increase in the number of small glaciers due to fragmentation. The average annual decrease (AAD) in glacier area has risen by about 1 order of magnitude from 1860–1990 (Livigno: 0.45; Orobie: 0.42; and Disgrazia: 0.39 % a−1) to 1990–2007 (Livigno: 3.08; Orobie: 2.44; and Disgrazia: 2.27 % a−1). This ranking changes when considering glaciers smaller than 0.5 km2 only (i.e., we remove the confounding caused by large glaciers in Disgrazia), so that post-1990 AAD follows the latitudinal gradient and Orobie glaciers stand out (Livigno: 4.07; Disgrazia: 3.57; and Orobie: 2.47 % a−1). More recent (2007–2013) field-based mass balances in three selected small glaciers confirm post-1990 trends showing the consistently highest retreat in continental Livigno and minimal area loss in maritime Orobie, with Disgrazia displaying transitional behavior. We argue that the recent resilience of glaciers in Orobie is a consequence of their decoupling from synoptic atmospheric temperature trends, a decoupling that arises from the combination of local topographic configuration (i.e., deep, north-facing cirques) and high winter precipitation, which ensures high snow-avalanche supply, as well as high summer shading and sheltering. Our hypothesis is further supported by the lack of correlations between glacier change and glacier attributes in Orobie, as well as by the higher variability in ELA,sub>0 positioning, post-LIA glacier change, and interannual mass balances, as we move southward along the transect.

In this paper we quantify the sediment dynamics in the formerly glaciated Ziel- bach catchment in the Italian Alps from the end of the Last Glacial Maximum (LGM) until today. As a basis for our quantifica- tion, we use the stratigraphic record offered by a 3.5 km2 large fan that we explore with a seismic survey, stratigraphic analyses of drillhole material, and 14C ages measured on organic matter encountered in these drill- ings. In addition, we calculate past denuda- tion rate variability in the fan deposits using concentrations of cosmogenic 10Be. We merge this information into a scenario of how the sediment flux has changed through time and how this variability can be related to cli- matic variations, framed within well-known paraglacial models. The results document a highly complex natural system. From the LGM to the very early Holocene, ice-melted discharge and climate variability promoted a high sediment flux (sedimentation rate up to 40 mm/yr). This flux then dramatically decreased toward interglacial values (0.8 mm/yr at 5–4 calibrated kyr B.P.). However, in contrast to the trend of classic paraglacial models, the flux recorded at Zielbach shows secondary peaks at 6.5 ka and 2.5 ka, with values of 13 mm/yr and 1.5 mm/yr, respec- tively. Paleo-denudation rates also decrease from ~33 mm/yr at the beginning of the Holocene to 0.42 mm/yr at 5 ka, with peaks of ~6 mm/yr and 1.1 mm/yr at 6.5 ka and 2.5 ka. High-amplitude climate change is the most likely cause of the secondary peaks, but anthropogenic activities may have contrib- uted as well. The good correlation between paleo-sedimentation and paleo-denudation rates suggests that the majority of the degla- ciated material destocked from the Zielbach catchment is stored in the alluvial fan. In this paper we quantify the sediment dynamics in the formerly glaciated Zielbach catchment in the Italian Alps from the end of the Last Glacial Maximum (LGM) until today. As a basis for our quantification, we use the stratigraphic record offered by a 3.5 km2 large fan that we explore with a seismic survey, stratigraphic analyses of drillhole material, and 14C ages measured on organic matter encountered in these drillings. In addition, we calculate past denudation rate variability in the fan deposits using concentrations of cosmogenic 10Be. We merge this information into a scenario of how the sediment flux has changed through time and how this variability can be related to climatic variations, framed within well-known paraglacial models. The results document a highly complex natural system. From the LGM to the very early Holocene, ice-melted discharge and climate variability promoted a high sediment flux (sedimentation rate up to 40 mm/yr). This flux then dramatically decreased toward interglacial values (0.8 mm/yr at 5-4 calibrated kyr B.P.). However, in contrast to the trend of classic paraglacial models, the flux recorded at Zielbach shows secondary peaks at 6.5 ka and 2.5 ka, with values of 13 mm/yr and 1.5 mm/yr, respectively. Paleo-denudation rates also decrease from ̃33 mm/yr at the beginning of the Holo cene to 0.42 mm/yr at 5 ka, with peaks of ̃6 mm/yr and 1.1 mm/yr at 6.5 ka and 2.5 ka. High-amplitude climate change is the most likely cause of the secondary peaks, but anthro pogenic activities may have contributed as well. The good correlation between paleo-sedimentation and paleo-denudation rates suggests that the majority of the deglaciated material destocked from the Zielbach catchment is stored in the alluvial fan. © 2014 Geological Society of America.

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.

article i nfo This study examines channel-reach morphology and bedload yield dynamics in relation to landscape structure and snowmelt hydrology in headwater streams of the Columbia Mountains, Canada. Data collection relies on field surveys and geographic information systems analysis in conjunction with a nested monitoring network of water discharge and bedload transfer. The landscape is characterized by subdued, formerly- glaciated upland topography in which the geomorphic significance of landslides and debris flows is negligible and fluvial processes prevail. While the spatial organization of channel morphology is chiefly controlled by glacially imposed local slope in conjunction with wood abundance and availability of glacigenic deposits, downstream patterns of the coarse grain-size fraction, bankfull width, bankfull depth, and stream power are all insensitive to systematic changes of local slope along the typically stepped long profiles. This is an indication that these alluvial systems have adjusted to the contemporary snowmelt-driven water and sediment transport regimes, and as such are able to compensate for the glacially-imposed boundary conditions. Bedload specific yield increases with drainage area suggesting that fluvial re-mobilization of glacial and paraglacial deposits dominate the sedimentary dynamics of basins as small as 2 km 2 . Stepwise multiple regression analysis shows that annual rates of sediment transfer are mainly controlled by the number of peak events over threshold discharge. During such events, repeated destabilization of channel bed armoring and re-mobilization of sedi- ment temporarily stored behind LWD structures can generate bedload transport across the entire snowmelt season. In particular, channel morphology controls the variability of bedload response to hydrologic forcing. In the present case studies, we show that the observed spatial variability in annual bedload yield appears to be modulated by inter-basin differences in morphometric characteristics, among which slope aspect plays a critical part.

Debris flow is an efficient process of sediment transfer from slope base to piedmont depositional fans in mountain drainage basins. To advance understanding of debris-flow sediment dynamics at the regional scale, we analyze a historical (1998–2009) database of debris flows from 77 basins of Alto Adige Province, northeastern Italy. By combining information on event volumetric deposition, high-resolution digital topography, and Quaternary sediment mapping we are able to link debris-flow sediment flux to morphometry, lithologic variability, and sediment availability. We show that basin-wide specific sediment yield (SSY) scales as an inverse power function of basin area. This function is strongly controlled by the way rock type and abundance of Quaternary deposits affect the rate of downstream sediment recruitment. When sediment flux associated with each debris-flow event is subsumed across discrete spatial increments of the entire region, a complex sedimentary signature in the area-SSY space is apparent. That is, SSY increases downstream up to areas as large as 1 km2, and starts to decline beyond this scale, regardless of sediment availability. We propose that this area-SSY relation is characteristic of debris flow–dominated settings.

[1] We examine the spatial distribution of channel-reach morphologies in formerly glaciated mountain drainage basins of coastal British Columbia, Canada. Using field- and geographic information systems-derived data, we show that the local channel slope and the degree of colluvial-alluvial coupling imposed by the glacial valley morphology dictate the spatial organization of channel types. In particular, the complex, glacially induced channel long profile produces characteristic sequences of channel reaches that depart from the downstream succession (colluvial/boulder-cascade/step-pool/rapids/riffle-pool) distinctive of simple unglaciated mountain streams. Typically, 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. We document that channel types are well separated in plots of slope versus shear stress, area versus shear stress, and slope versus relative roughness. In agreement with these outcomes, multivariate discriminant analyses coupled with principal component analysis of 98 study reaches yield a highly successful channel-type classification when slope, shear stress, and relative roughness are considered. Success rates, depending on whether or not boulder-cascade reaches are pooled together with step-pools, are 88% and 75%, respectively. Previous work in unglaciated settings has suggested that mountain channels have distinct bed morphology states that vary primarily with slope; our study reveals that even in formerly glaciated valleys, where slope is largely inherited from glacial times, these distinct bed states exist and vary (mostly) with slope, adding considerable strength to this empirical knowledge.

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 glaciated landscapes is examined by analyzing the structure of geomorphic process domains and channel long profiles. To identify process domains we use channel surveys and GIS analysis to construct slope-area transects of the channel network. This 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 (contributing area

The impacts of logging activities on mass wasting were examined in five watersheds in the coastal mountains of British Columbia. Historical aerial photos were used to document mass wasting events, and their occurrence was related to logging activities in the study basins. Logged and forested areas were compared in terms of mass wasting magnitude and frequency, with reference to site characteristics. The recovery time of the landscape after logging was assessed. Bedrock type and basin physiography had no identifiable effect on mass wasting frequency and magnitude. Mass wasting failure was primarily controlled by slope gradient. Basin vulnerability increased, following clearcutting relative to forested areas, in that mass wasting was initiated on gentler slopes. The volume of sediment produced from logged slopes is of the same order as that from forested areas, which are steeper by as much as 10°. In both logged and forested areas, the size distribution of mass wasting events follows an exponential distribution. However, the variability in mass wasting size in forested areas is much higher than that obtained for logged areas. The recovery time after forest harvesting is over 20 years, which confirms published estimates based on vegetation reestablishment. Continuous disturbance of the basin, however, may extend the recovery time for the whole basin well beyond 20 years. © 2002 Elsevier Sciece B.V. All rights reserved.