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In the warming Arctic, retrogressive thaw slumping (RTS) has emerged as the primary thermokarst modifier of ice-rich permafrost slopes, raising urgency to investigate the distribution and intensification of disturbances and the cascade of effects. Tracking RTS is challenging due to the constraints of remote sensing products and a narrow understanding of complex, thaw-driven landforms; however, high-resolution elevation models provide new insights into geomorphic change. Structural traits, such as RTS depth of thaw or volume, can be obtained through allometric scaling. To address fundamental knowledge gaps related to area–volume scaling of RTS, a suitable surface interpolation technique was first needed to model pre-disturbance topography upon which volume estimates could be based. Among eight methods with 32 parameterizations, natural neighbour surface interpolation achieved the best precision in reconstructing pre-disturbed slope topography (90th percentile root mean square difference ±1.0 m). An inverse association between RTS volume and relative volumetric error was observed, with uncertainties < 10 % for large slumps and < 20 % for small to medium slumps. Second, a multisource slump inventory (MSI) for two study areas in the Beaufort Delta (Canada) region was developed to characterize the diverse range of disturbance morphologies and activity levels, which provided consistent characterization of thaw-slump-affected slopes between regions and through time. The MSI delineation of high-resolution hillshade digital elevation models (DEMs) for three time periods (airborne stereo-imagery, lidar, ArcticDEM) revealed temporal and spatial trends in these chronic mass-wasting features. For example, in the Tuktoyaktuk Coastlands, a + 38 % increase in active RTS counts and + 69 % increase in total active surface area were observed between 2004 and 2016. However, the total disturbance area of RTS-affected terrain did not change considerably (+ 3.5 %) because the vast majority of active thaw slumping processes occurred in association with past disturbances. Interpretation of thaw-driven change is thus dependent on how active RTS is defined to support disturbance inventories. Our results highlight that active RTS is tightly linked to past disturbances, underscoring the importance of inventorying inactive scar areas. Third, the pre-disturbance topographies, MSI digitizations, and DEMs were integrated to explore allometric scaling relationships between RTS area and eroded volume. The power-law model indicated non-linearity in the rates of RTS expansion and intensification across scales (adj- R2 of 0.85, n= 1522) but also revealed that elongated, shoreline RTS reflects outliers poorly represented by the modelling. These results indicate that variation in the allometric scaling of RTS populations is based on morphometry, terrain position, and complexity of the disturbance area, as well as the method and ontology by which slumps are inventoried. This study highlights the importance of linking field-based knowledge to feature identification and the utility of high-resolution DEMs in quantifying rates of RTS erosion beyond tracking changes in the planimetric area. [ABSTRACT FROM AUTHOR]

In New Zealand's East Cape, gully complexes are a major component of catchment sediment budgets, and they drive persistent river dynamism, including catastrophic aggradation and braid-channel avulsion. Despite their overwhelming influence on the sediment cascade, the genesis of these complexes is poorly understood. In this paper, we reconstructed the initiation of one such gully complex and the associated debris train, which fills a second-order valley to more than 40 m and significantly impacts the trunk channel. Cut-and-fill analyses (1957-2012-2015) using light detection and ranging (LiDAR) and structure-from-motion (SfM) data suggest the valley-fill deposit totals 6.87 × 106 m³, with historic aggradation rates of almost 1 m yr-1. This long-term perspective was made possible through the combination of archival aerial photos and SfM techniques. The sediment delivery ratio between the scar zone and the main-stem Raukokore River had a long-term average of 20% over the first 55 yr, as the valley was filled and the deposit steepened. In the last 3 yr, the ratio was 74%, suggesting improved efficiency in delivery. This considerable increase in connectivity resulted from the rapid aggradation of the debris train, which achieved a quasi-linear profile with mean slope of 0.077 m m-1 by 2015. The major implication of this work is that the peak effects of these long-lived, valley-filling features arrive decades after the initial disturbance. Digital elevation models of difference from SfM techniques provide numerous insights into the changing configuration of gully-deposit-trunk channel linkages, which govern this temporal change in sediment delivery. Moreover, the presence of many such complexes in the soft-rock, steepland terrain of the Waikura, Whangaparaoa, and Raukokore Rivers, and notable absence from the Motu River, suggests their distribution is primarily controlled by lithology rather than land use. Given the vast stores of unconsolidated sediment in valley fills such as this, the regime of river aggradation is likely to continue for decades. [ABSTRACT FROM AUTHOR]

The Waiapu River catchment (drainage area of 1734-km 2 ) is one of the most prolific conveyors of sediment in the world, annually delivering roughly 35 Mt of fine material to the ocean from eroding gullies, hillslopes, and reworked sediment on valley floors. Tectonic and geologic influences, in combination with a dynamic climate influenced by tropical cyclones and clearance of vegetation from steep hillslopes, predisposes this region to high rates of erosion. The bedload sediment regime of the river is strongly influenced by several exceptionally large gullies and gully complexes that produce a coarse-grained, poorly sorted sediment mixture. Rapid abrasion and breakdown leads to high rates of suspended sediment yield. A wave of bedload material, manifesting as elevated bed levels and significant widening of active alluvial fills, has been triggered by large inputs of hillslope material from a few key tributary catchments following Cyclone Bola in 1988. We review the evidence for the relaxation process of the sedimentary system in the subsequent 29 years, appraising some of the legacy effects that may endure, as associated with reworking of the considerable alluvial stores within the Waiapu system. We use Structure-from-Motion (SfM) techniques and archival aerial photos to quantify changes in sediment storage at the base of two major gully systems in recent decades. A record of over 850 cross section surveys at 62 sites on 10 rivers throughout the catchment (1958–2017) indicates recent transition from a trend of continuous accumulation to downcutting and remobilisation of valley-bottom deposits. The channel cross sections provide a minimum estimate of sediment flux from source areas to the lower reaches of the river, giving a rudimentary but spatially extensive picture of the wave of material cascading through the drainage network. The largest impacts occur in the upper steepland rivers, closest to the landslide-derived sediment supply. Transport rates here, as inferred from cross section change, are at a maximum during an aggradational phase following Cyclone Bola then taper off, despite the large sediment accumulations remaining in the system. As of 2017, the river is in the process of incising the upper extents of this deposit on a trajectory of recovery toward pre-Bola conditions. The compilation of cross section data provides us with new insights into the sensitivity of particular sites in the landscape, as well as the changing relationship between reach sediment storage and transport rates during the response and relaxation phase of a major disturbance in a large catchment. [ABSTRACT FROM AUTHOR]

Lateral inputs from hillslopes and tributaries exert a variable impact upon the longitudinal connectivity of sediment transfer in river systems with differing drainage network configurations. Network topology influences channel slope and confinement at confluence zones, thereby affecting patterns of sediment storage and the conveyance of sediments through catchments. Rates of disturbance response, patterns of sediment propagation, and the implications for connectivity and recovery were assessed in two neighbouring catchments with differing network configurations on the East Cape of New Zealand. Both catchments were subject to forest clearing in the late 1940s and a major cyclonic storm in 1988. However, reconstruction of landslide runout pathways, and characterization of connectivity using a Tokunaga framework, demonstrates different patterns and rates of sediment transfer and storage in a dendritic network relative to a more elongate, herringbone drainage network. The dendritic network has a higher rate of sediment transfer between storage sites in successive Strahler orders, whereas longitudinal connectivity along the fourth-order mainstem is disrupted by lateral sediment inputs from multiple low-order tributaries in the more elongate, herringbone network. In both cases the most dynamic (‘hotspot’) reaches are associated with a high degree of network side-branching. [ABSTRACT FROM AUTHOR]

Tunnicliffe, J., Church, M. & Enkin, R. J. 2012 (January): Postglacial sediment yield to Chilliwack Lake, British Columbia, Canada. Boreas, Vol. 41, pp. 84-101. 10.1111/j.1502-3885.2011.00219.x. ISSN 0300-9483. Seismic records and evidence from sediment cores at Chilliwack Lake provide the basis for a long-term (postglacial) sediment budget for a 324-km2 Cordilleran catchment. Chilliwack Lake (11.8 km2 surface area), situated in the North Cascade Mountains, near Chilliwack, British Columbia, was formed behind a valley-wide recessional moraine in the final phase of post-Fraser alpine glaciation. Seismic surveys highlight the postglacial lacustrine record, which is underlain by a thick layer of sediments related to deglacial sedimentation. Sediment cores provide details of grain-size fining from the delta to the distal lake basin. The cores also show a record of intermittent fire and debris flows. Magnetic measurements of lake sediments provide information on grain size, as well as a dating framework. The total postglacial lake-floor deposit volume is estimated to be 397 ± 27 × 106 m3. Including estimates of fan and delta deposition, the specific postglacial yield to the lake is calculated to be ∼86 ± 13 Mg km2 a−1. The sediment volume in the uppermost (Holocene) lacustrine layer is 128 ± 9 × 106 m3, representing ∼41 ± 4 Mg km2 a−1 in the Holocene. Compared with other Cordilleran lakes of similar size, particularly those with glacial cover in the watershed, Chilliwack Lake has experienced relatively modest rates of sediment accumulation. This study provides an important contribution to a growing database of long-term (postglacial) sediment yield data for major Cordilleran lakes, essential for advancing our understanding of the pace of landscape evolution in formerly glaciated mountainous regions. [ABSTRACT FROM AUTHOR]

• Climate change would cause an increasing trend for temperatures and decreasing amount of precipitation. • Climate change would contribute to a drier condition in the upper Siem Reap catchment. • Climate change could influence on water supply of the Angkor Temple Complex, livelihood of the people and cultivation. • Forest plantation is an effective and practical solution to cope with climate change. Cambodia is one of the most vulnerable countries to climate change impacts such as floods and droughts. Study of future climate change and drought conditions in the upper Siem Reap River catchment is vital because this river plays a crucial role in maintaining the Angkor Temple Complex and livelihood of the local population since 12th century. The resolution of climate data from Global Circulation Models (GCM) is too coarse to employ effectively at the watershed scale, and therefore downscaling of the dataset is required. Artificial neural network (ANN) and Statistical Downscaling Model (SDSM) models were applied in this study to downscale precipitation and temperatures from three Representative Concentration Pathways (RCP 2.6, RCP 4.5 and RCP 8.5 scenarios) from Global Climate Model data of the Canadian Earth System Model (CanESM2) on a daily and monthly basis. The Standardized Precipitation Index (SPI) and Standardized Precipitation Evapotranspiration Index (SPEI) were adopted to develop criteria for dry and wet conditions in the catchment. Trend detection of climate parameters and drought indices were assessed using the Mann-Kendall test. It was observed that the ANN and SDSM models performed well in downscaling monthly precipitation and temperature, as well as daily temperature, but not daily precipitation. Every scenario indicated that there would be significant warming and decreasing precipitation which contribute to mild drought. The results of this study provide valuable information for decision makers since climate change may potentially impact future water supply of the Angkor Temple Complex (a World Heritage Site). [ABSTRACT FROM AUTHOR]

Large wood (LW) commonly forms log jams, influencing bed composition and biota via complex flow-sediment-wood interactions. A LW blockage, often induced by river-crossing infrastructure, can strongly alter channel hydraulics and sediment transport patterns, thus inducing a 'forced' channel morphology. For studying the deposition of bedload gravel fractions in the presence of a rigid LW jam, a novel experimental setup is presented. Using a mobile bed stream table, the effects of a channel-spanning blockage (a 'dam jam'), resting at a bridge pier, on sediment transport and scour dynamics are examined. Changes in channel morphology were measured using Structure from Motion (SfM) photogrammetry and manually obtained bedload measurements. For the experiment without LW accumulation in place, natural bedload transport was observed over the entire channel length - about 20% of fed colour gravel was recovered from the sediment trap at the outlet, while a total bedload interruption occurred in presence of the LW accumulation, resulting in trapping all fed gravel material upstream of the obstructed cross-section. The volumetric deviation between SfM and manual measurements was less than 0,4%. The porosity characteristics of the LW accumulation were analysed using volumetric meshing techniques. With our experiments, we demonstrated that a relatively high log jam porosity has significant impact on channel morphology. By interrupting the hydraulic energy gradient, the movement of coarse sediment transport is damped, forcing deposition and initiating the development of a sediment wedge upstream of the infrastructure. Our quantitative results provide new insights into how LW can force channel morphology (particularly sediment storage) through the alteration of channel hydraulics. We further elaborate on how novel laboratory-based SfM techniques can be used to enhance the current understanding of complex flow-sediment-wood interaction processes at engineered in-stream structures. In a laboratory study, we used Structure from Motion (SfM) photogrammetry and manually-obtained sediment transport measurements to quantify how a large wood (LW) accumulation can lead to a total interruption of bedload transport processes in a river section. With the introduction of a LW blockage, we observed substantial deposition of all gravel size fraction previously in motion. The laboratory model provides an effective demonstration of how storage dynamics in streams with large jams can be moderated by wood. Unlabelled Image [ABSTRACT FROM AUTHOR]

The formation of large wood (LW) accumulations during floods represents a major hazard for constricted river cross-sections, e.g. bridges and weirs, as it affects flow hydraulics and sediment transport. To better assess LW accumulations, reliable strategies and techniques are required. There are currently practical limits on monitoring accumulation configurations. Both laser scans and photogrammetric techniques can be used to scan the outer contours of LW accumulations, but cannot practically assess the wood content and porosity. Details of the outer deposit are captured in high resolution, but the core of the deposit remains occluded, and estimation is necessary. This becomes more challenging for deposits of increasing size (relative to wood elements). To develop a more efficient workflow for LW accumulation assessment in the field, we performed a laboratory study to develop a relationship between the envelope volume of water-worked LW jams during a single flood hydrograph and the volume of woody elements within (explicitly accounting for porosity). We used photogrammetric techniques, now in common use for reconnaissance surveys of debris accumulations, on wood accumulations scaled for the laboratory. The study's aim is to develop a semi-automated assessment method, enabling efficient image acquisition, processing and computation of LW accumulation volume. Using a multi-camera array above the laboratory channel, and applying Structure from Motion photogrammetry, we developed 3D models for 16 experimental flow-formed wood accumulations, each with >50 individual wooden dowels. No correlations were found between porosity and flow magnitude; porosity was found to be similar for most deposits (~66%). As a result of this accumulation structure, the envelope volume used in 3D and 2.5D photogrammetric methods tended to overestimate wood content by 3× and 2.6×, respectively. The results obtained here will contribute to a more reliable volumetric assessment for inventories of wood mass in river systems. • Structure from Motion (SfM) photogrammetry is applied to log jam assessment. • Semi-automated computation of large wood (LW) accumulation volume and porosity • Porosity of LW accumulations was found to be similar for most experiments (~66%). • Results reveal consistency of jam porosity with mathematical models of cylinders. • A cost-efficient approach for future application in LW management is presented. [ABSTRACT FROM AUTHOR]

• Novel experimental setup using scaled large wood (LW) accumulations in the laboratory. • Structure from Motion (SfM) photogrammetry successfully applied in LW research. • Volume assessment of LW accumulations in 2.5D and 3D resolution by means of SfM. • Porosity estimates of LW accumulations from 2.5D and 3D volumetric measurements. • Generation of high quality point cloud and watertight 3D mesh accumulation models. A Structure from Motion (SfM) photogrammetry-based methodology for precise mapping of large wood (LW) accumulations in fluvial systems is presented. The technique may be useful for routine inventory and rapid volume estimation of complex LW structures that tend to divert or obstruct flow in rivers. Our methodology is validated by means of laboratory experiments, ranging from elementary to complex arrangements of LW components and organic fine material (OFM). Seven experimental setups were used as the basis for (i) manual approximations of 2.5D and 3D geometric reference volumes, (ii) 2.5D volume models based on mesh geometry, (iii) a closed ('watertight') 3D mesh from an unorganized point cloud and (iv) estimates of porosity. A commercially available SfM photogrammetry software package, Pix4Dmapper, was used for point cloud and simplified mesh generation. In order to obtain more precise volumes, 3D surface models are required. Accordingly, we generated 3D watertight mesh models of the unorganized point cloud using the screened Poisson Surface Reconstruction (PSR) technique. The Pix4D volume tool (2.5D) resulted in an overestimation (2.9 to 52.7%) of the geometric volume (3D), due to the convex hull approximation of the geometry normal to the surface plane. PSR (3D) resulted in more precise volumes, showing deviations from the geometric volume (3D) in a range of −15.9 to +10.6%, as the algorithm could capture concavities and involuted surfaces on the accumulation. Assuming that the difference between 3D and 2.5D volume models represents many of the voids visible within or on the surface of the deposit, this volume can be used as an estimate of porosity. Our assessment suggests that image-based SfM methodology is well-suited for further investigations in LW research, due to its time and cost efficiency in comparison with other conventional surveying techniques. The methodology can be used to generate high quality point cloud and mesh models of log jam formations; these may be used by river managers and researchers to quantify accumulation volume and thus gain a better understanding of LW composition and the influence of wood geometry on hydraulic flow conditions. [ABSTRACT FROM AUTHOR]

River systems in forested catchments are strongly influenced by wood and sediment loading from both natural (e.g. mass wasting) and anthropogenic (forestry) sources. In order to effectively manage impacts on property, infrastructure and the broader ecosystem, as well as to better assess the interactions between large wood (LW), channel morphology and flow hydraulics, more efficient and accurate surveying techniques are required. We present an evaluation of Structure from Motion (SfM) photogrammetry and point-cloud-based techniques for capturing the geometry and volume of LW in the field. Wood accumulations can be notoriously complex 3D objects, with multi-scalar features, and thus difficult to quantify with photogrammetric methods. We introduce a novel workflow to generate volumetric information of organic material accumulations, using SfM and a suite of meshing algorithms. The volumes of two accumulations are assessed individually, using several meshing techniques, and are compared with more conventional volume estimates. Results show volumetric variations of <19% between the interpolated volumes from point clouds and those of meshes, and a slight overestimation of volumes using simple geometric primitives. We discuss the nature of noise and errors that arise within processed results from SfM software (Pix4D) and offer some criteria for generating high quality point cloud models of highly irregular and complex organic material piles. More detailed 3D mesh representations of LW accumulations will be effective for improving computer-aided modelling of jam-induced floods, backwater effects and impacts on channel morphology. Measuring the size and geometric distributions of wood elements, assessing deposit volume and porosity, or estimating the proportion of organic fine material in the deposit, are important quantities to be assessed for wood accumulations in rivers. The photogrammetric methodology presented herewith will be useful for forestry and freshwater managers to estimate LW quantities, but also to develop accurate 3D models of prototype LW accumulations, independent of camera model and environmental condition, for a range of applications and LW accumulation assessment. • Presenting a novel technique for volume estimation of large wood (LW) accumulations • Introducing Structure from Motion (SfM) photogrammetry for volumetric jam assessment • Discussing observed volumetric deviations caused by using various meshing approaches • A flexible, time and cost-efficient approach for generating high resolution models • Obtained models show potential for application in computational fluid dynamics (CFD). [ABSTRACT FROM AUTHOR]

Contemporary management practices have artificially confined (strangled) river systems in Aotearoa New Zealand to support intensified land use in riparian areas. These practices work against nature, diminishing the functionality and biodiversity values of living rivers, and associated socio‐cultural relations with rivers. River confinement can accentuate flood risk by promoting development in vulnerable locations and limiting the flexibility to adapt to changing climate, prospectively accentuating future disasters. To date, uptake of space‐to‐move management interventions that seek to address such shortcomings is yet to happen in Aotearoa New Zealand. This is despite the fact that such practices directly align with Māori (indigenous) conceptualizations of rivers as indivisible, living entities. Treaty of Waitangi obligations that assert Māori rights alongside colonial rights of a settler society provide an additional driver for uptake of space‐to‐move initiatives. This article outlines a biophysical prioritization framework to support the development and roll out of space‐to‐move interventions in ways that work with the character, behavior, condition, and evolutionary trajectory (recovery potential) of each river system in Aotearoa. This article is categorized under:Water and Life > Conservation, Management, and AwarenessScience of Water > Water and Environmental Change [ABSTRACT FROM AUTHOR]

Landslides are widespread geomorphological features on the North Island of New Zealand, where they represent one of the primary landscape-forming processes. This study focuses on the steepland terrain surrounding Gisborne, a city located on the east coast of the North Island, at the Hikurangi subduction margin. This terrain consists of young, weak, sedimentary rocks and soils; the most common modes of slope failures are soil creep, slides and flows in shallow, clay-rich soil and regolith, triggered by heavy rainfall. Based on observational data from Sentinel-1 imagery, this study leverages results from interferometric synthetic aperture radar (InSAR) processing to reveal the distribution of deformation across Gisborne's steepland periphery from January 2016 to December 2021. Velocities in the line of sight were obtained from the stack of interferograms and projected along the direction of maximum slope, to extract the true displacement on the slopes. The ascending and descending data sets were combined to reveal the vertical and horizontal components of the deformation. The results were combined with a regional LiDAR data set, aerial imagery and field observations to delineate areas of slope deformation. Finally, slope deformation time series data was compared with rainfall records to identify seasonal changes, due to shrinking and swelling of expansive soils. Although the InSAR displacement data contains some noise, results could be used to identify 132 unstable slopes within the study area, caused by soil creep and earthflows. Also, the shrink-swell of expansive soils causes a seasonal pattern of displacements, which varied by 10–20 mm/year between Austral winter and summer, strongly correlated to rainfall. [ABSTRACT FROM AUTHOR]

Ice-marginal glaciated landscapes demarcate former boundaries of the continental ice sheets. Throughout circumpolar regions, permafrost has preserved relict ground ice and glacigenic sediments, delaying the sequence of postglacial landscape change that transformed temperate environments millennia earlier. Here we show that within 7 × 106 km2 of glaciated permafrost terrain, extensive landscapes remain poised for major climate-driven change. Across northwestern Canada, 60-100-km-wide concentric swaths of thaw slump-affected terrain delineate the maximum and recessional positions of the Laurentide Ice Sheet. These landscapes comprise ~17% of continuous permafrost terrain in a 1.27 × 106 km2 study area, indicating widespread preservation of late Pleistocene ground ice. These thaw slump, relict ground ice, and glacigenic terrain associations are also evident at the circumpolar scale. Recent intensification of thaw slumping across northwestern Canada has mobilized primary glacial sediments, triggering a cascade of fluvial, lacustrine, and coastal effects. These geologically significant processes, highlighted by the spatial distribution of thaw slumps and patterns of fluvial sediment mobilization, signal the climate-driven renewal of deglaciation and postglacial permafrost landscape evolution. [ABSTRACT FROM AUTHOR]

The East Coast region of New Zealand has some of the highest erosion rates in the world, due to its proximity to an active plate boundary, susceptibility to high-intensity storms and steep terrain underlain by young soft sedimentary rock and soil. In the city of Gisborne, expansion of residential blocks into steeper terrain in peri-urban areas has required improved capacity for the characterisation and monitoring of slope stability. Landslides have affected several properties and have destroyed infrastructure. Slope failure commonly occurs during heavy rainfall events when slow-moving retrogressive slides transition into earthflows and mudflows. In this study, we used in situ sampling and testing methods combined with remote sensing techniques to provide an understanding of the pre-failure and post-failure behaviour of an urban landslide in Gisborne. High-resolution aerial imagery, unmanned aerial vehicle imagery and light detection and ranging data revealed slope morphology and contours of prehistoric failures in the area, and highlighted the more recent impacts of deforestation on slope stability. Furthermore, Sentinel-1 InSAR analysis determined that gradual deformation began in 2017, following two ex-tropical cyclone events. Deformation downslope continued until an initial failure in July 2020. Following that event, some parts of the slope proceeded to accelerate, leading to a further reactivation event in November 2021, following heavy rainfall. During this November 2021 event, average line of sight velocities ranged from −7.9 to −11.2 mm/year, and deformation rates in the vertical direction (related to rotational slumping) averaged −11.2 to −11.9 mm/year, consistent with field observations. [ABSTRACT FROM AUTHOR]

Magnetically tagged particles were used to investigate the effects of sockeye salmon (Oncorhynchus nerka) and floods on the dispersion of coarse bed material in the Stuart-Takla region, British Columbia, Canada. The dominant annual sediment transporting event in the channels is the snowmelt flood events, with lesser activity usually accomplished during summer floods. Annually in August, the channel bed material is reworked by the Early Stuart sockeye salmon spawning, as the fish excavate the streambed to deposit and bury their eggs. These nesting cavities are called redds. Results from 67 tracer recovery experiments over five years were highly variable, subject to the magnitude of floods and the returning population of salmon. Overall, the depositional pattern from nival flood events usually demonstrated a high degree of clast mobilization, long travel distances (up to 150 m), and mean depths of burial up to 18 cm. Summer flood events showed somewhat lower rates of mobilization, distances of travel, and depths of burial. Although the fish did not move the tracers very far, their effect on the bed was generally quite pervasive -- up to 100 percent of the clasts were mobilized, and the depth of burial was considerable (mean burial depths up to 14 cm). The amount of vertical mixing of sediment by salmon was often on the same order of magnitude as flood events. The significant vertical mixing of sediments by the fish has important implications for the mobility of sediment in the stream. Since any armoring layer formed during high flows throughout the year is subject to the bioturbation of salmon, this suggests that the transport threshold in the creeks remains relatively low. Salmon likely play an integral role in the sediment transport dynamics and annual sediment budget of the lower reaches of these creeks. [ABSTRACT FROM AUTHOR]

The intensification of thaw-driven mass wasting is transforming glacially conditioned permafrost terrain, coupling slopes with aquatic systems, and triggering a cascade of downstream effects. Within the context of recent, rapidly evolving climate controls on the geomorphology of permafrost terrain, we (A) quantify three-dimensional retrogressive thaw slump enlargement and describe the processes and thresholds coupling slopes to downstream systems, (B) investigate catchment-scale patterns of slope thermokarst impacts and the geomorphic implications, and (C) map the propagation of effects through hydrological networks draining permafrost terrain of northwestern Canada. Power-law relationships between retrogressive thaw slump area and volume (R2=0.90) , as well as the thickness of permafrost thawed (R2=0.63), combined with the multi-decadal (1986–2018) increase in the areal extent of thaw slump disturbance, show a 2 order of magnitude increase in catchment-scale geomorphic activity and the coupling of slope and hydrological systems. Predominant effects are to first- and second-order streams where sediment delivery, often indicated by formation of recent debris tongue deposits, commonly exceeds the transport capacity of headwater streams by orders of magnitude, signaling centennial- to millennial-scale perturbation of downstream systems. Assessment of hydrological networks indicates that thaw-driven mass wasting directly affects over 5538 km of stream segments, 889 km of coastline, and 1379 lakes in the 994 860 km2 study area. Downstream propagation of slope thermokarst indicates a potential increase in the number of affected lakes by at least a factor of 4 (n>5692) and impacted stream length by a factor of 8 (>44343 km), and it defines several major impact zones on lakes, deltas, and coastal areas. Prince of Wales Strait is the receiving marine environment for greatly increased sediment and geochemical fluxes from numerous slump-impacted hydrological networks draining Banks Island and Victoria Island. The Peel and Mackenzie rivers are globally significant conveyors of the slope thermokarst cascade, delivering effects to North America's largest Arctic delta and the Beaufort Sea. Climate-driven erosion of ice-rich slopes in permafrost-preserved glaciated terrain has triggered a time-transient cascade of downstream effects that signal the rejuvenation of post-glacial landscape evolution. Glacial legacy, ground-ice conditions, and continental drainage patterns dictate that terrestrial, freshwater, coastal, and marine environments of western Arctic Canada will be an interconnected hotspot of thaw-driven change through the coming millennia. [ABSTRACT FROM AUTHOR]

The historically unstable Sunkist Bay cliff in Auckland, New Zealand, is formed of weak Pleistocene alluvial sediments, infilling a paleovalley eroded into Miocene sandstone. Weathered tephra layers dip at low angles out of the cliff, and part-control stability. The last major failure prior to 2017 occurred in 2011, immediately to the west of the 2017 failure. Despite the long-term history of instability, over the last two decades, residential property construction has continued to < 10 m of the cliff edge. On 5 April 2017, ex-tropical cyclone Debbie delivered 157 mm of rainfall in 24 h, the 3rd highest 24-h total in 40 years. This was preceded 1 month earlier by 210 mm of rainfall on 8 March (the 'Tasman Tempest' storm), locally a 1 in 100-year event. A seawall constructed at the base of the cliff may have acted to inhibit pore-water pressure reduction during March–April 2017, because horizontal drains were absent in the seawall directly in front of the 2017 slope failure. Irrespective of the exact process-mechanisms of the 2017 failure, this case study highlights the importance of careful land use planning and imposition of adequate setback distances in coastal zones in New Zealand, and globally. [ABSTRACT FROM AUTHOR]

Globally, rivers systems are under considerable and increasing threat from multiple anthropogenic stresses, including different types of direct (e.g. channel engineering) and indirect human impacts (e.g. land cover and land use changes) that alter water and sediment dynamics. (Dis)connectivity relationships determine the source, timing and rates of water and sediment flux in catchments and thus their geomorphic sensitivity to disturbance. However, most river and catchment management plans overlook the role of sediment (dis)connectivity. Here we use examples from different environmental settings with different sediment-related problems to show how understandings of sediment (dis)connectivity can inform catchment-based management plans. We focus on concerns for river conservation and recovery, using examples from Austria, New Zealand and Australia. Finally, we present questions for practitioners to consider to appropriately contextualise management applications when using (dis)connectivity concepts in practice. Our findings revealed that differences in sediment (dis)connectivity relationships exert profound catchment-specific variability in (eco)-geomorphic response to disturbance. Understanding (dis)connectivity and system history is therefore essential to forecast the effects of on-ground management actions. Unlabelled Image • Managing sediment (dis)connectivity is vital for proactive catchment action plans. • Geography and history (context) determine catchment-scale (dis)connectivity. • Human activities modify (dis)connectivity in different ways in different settings. • Altered (dis)connectivity relationships affect timeframes for geomorphic recovery. • Catchment-specific understandings are required to manage sediment (dis)connectivity. [ABSTRACT FROM AUTHOR]

Assessment of River Styles, accompanied by time series analysis of historic imagery and geomorphic change detection techniques are used to explain the capacity for river adjustment (geomorphic sensitivity) in relation to the distribution of stream power along 3000 km of channels (3rd Strahler order and greater) to better inform management initiatives in the Waipā catchment, the largest tributary of the Waikato River on the North Island of Aotearoa, New Zealand. Unlike most dynamically adjusting physical landscapes of Aotearoa, most reaches within the Waipā catchment are resistant to geomorphic change. Only 3% of the studied river length has experienced significant planform adjustment since the 1950s and is considered highly sensitive to adjustment. Contemporary alluvial dynamism is largely restricted to gravel bed reaches in high energy rivers within the piedmont zone. The capacity for lateral adjustment in headwater stream courses is restricted by the imprint of past volcanic activity. Further downstream capacity is also limited because of terrace constraints as a result of post-glacial base-level fall, and the entrenchment of the Waikato Fan. Anthropogenic modifications in the catchment include drained wetlands, straightened channels, reinforced banks and emplaced artificial levees (stopbanks) in the few reaches that were prone to adjustment. Highlighting geomorphologically-sensitive reaches at the catchment-scale helps to better prioritise rehabilitation efforts and to support the design and implementation of proactive management plans. [Display omitted] • Rivers in volcanic landscapes of the Waipā have limited capacity to adjust. • Geologic controls determine river geodiversity and sensitivity. • Anthropogenic impacts modify reaches that have capacity for geomorphic adjustment. • Sound management builds on coherent catchment-scale geomorphic understanding. [ABSTRACT FROM AUTHOR]

The article presents the authors response to the comments made by John M. Faustini to their research paper " "Sediment Dispersion in Salmon Spawning Streams: The Influence of Floods and Salmon Redd Construction. " According to the authors, the question of enhanced mobility is complex, and the relative influences of roughness elements and bed structure have not been well quantified. On the face of it, Faustini's observation is correct: the data as presented do not provide a particularly strong case for increased mobility of gravels. Their observations of vertical mixing of the bed suggest that salmon bioturbation likely improves the condition of spawning beds for future spawning. Faustini points out that this conclusion is not tenable based on the evidence presented, and is counter to Montgomery conclusion that surface coarsening and reduced mobility improves the chances of embryo survival. Faustini's suggestion of weighting the work done by spawning salmon by the percentage of clasts transported would seem to be a useful modification to their approach.

A correction to the article"Sediment Dispersion in Salmon Streams: The Influence of Floods and Salmon Redd Construction," that was published in the 2004 issue is presented.

Large wood (LW), delivered to the river channel in the course of commercial forest harvesting, or generated during natural events, can be mobilised during floods. The movement of wood along the river corridor involves complex cycles of recruitment, mobilisation, transportation and deposition. These processes are affected by the size, buoyancy, roughness and complexity of the wood components, as well as the relative spatial density and the character of the channel boundary elements. In order to understand the probabilistic behaviour of woody elements within the fluvial system, it is important to be able to characterise the timing, mechanisms and duration of the various phases of wood transport. Due to a lack of suitable sensing technology, a detailed understanding of LW recruitment, transport and accumulation processes has thus far been elusive. In this study we introduce a technique using a nine-degrees of freedom (9-DoF) sensor embedded in a 'SmartWood' dowel that shows strong potential for measuring and recording LW movement. The SmartWood assembly comprises an integrated sensor with an inertial measurement unit (IMU), accelerometer, gyroscope and magnetometer, installed in a wooden dowel that is scaled to represent a tree stem in the flume. The sensor is able to record the many different motions of LW transport. The sensor-tagged wood dowel is density-compensated, with a specific weight of 0.5 g·cm−3. A series of verification and experimental tests was carried out to evaluate the applicability of this new technology for LW research and is presented herewith. Experiments were conducted in a 6.3 m long and 1.5 m wide flume with sinuous channel course and mobile gravel bed conditions, with a discharge of up to 10 l·s−1. We show that LW movement during transport, particularly starting, rolling, yawing and stopping processes, but also LW impacts, can be quantified within a flume environment. These findings can be further developed to obtain the translational movement behaviour of LW, which is needed to refine probabilistic models of downstream trajectories. Understanding complex LW movement is essential for informing freshwater and forestry management guidelines. • Multi-axis smart sensor successfully applied in large wood (LW) research • Presentation of a smart sensor verification procedure. • Laboratory flume experiments using a sensor-tagged dowel reveal movement behaviour • Results allow for evaluation of LW recruitment, transport and accumulation processes • SmartWood may enable measuring of impact forces of logs on hydraulic infrastructure [ABSTRACT FROM AUTHOR]

Unmanned Aerial Vehicle (UAV) systems, sensors, and photogrammetric processing techniques have enabled timely and highly detailed three-dimensional surface reconstructions at a scale that bridges the gap between conventional remote-sensing and field-scale observations. In this work 29 rotary and fixed-wing UAV surveys were conducted during multiple field campaigns, totaling 47 flights and over 14.3 km2, to document permafrost thaw subsidence impacts on or close to road infrastructure in the Northwest Territories, Canada. This paper provides four case studies: (1) terrain models and orthomosaic time series revealed the morphology and daily to annual dynamics of thaw-driven mass wasting phenomenon (retrogressive thaw slumps; RTS). Scar zone cut volume estimates ranged between 3.2 × 103 and 5.9 × 106 m3. The annual net erosion of RTS surveyed ranged between 0.35 × 103 and 0.39 × 106 m3. The largest RTS produced a long debris tongue with an estimated volume of 1.9 × 106 m3. Downslope transport of scar zone and embankment fill materials was visualized using flow vectors, while thermal imaging revealed areas of exposed ground ice and mobile lobes of saturated, thawed materials. (2) Stratigraphic models were developed for RTS headwalls, delineating ground-ice bodies and stratigraphic unconformities. (3) In poorly drained areas along road embankments, UAV surveys detected seasonal terrain uplift and settlement of up to 0.5 m (>1700 m2 in extent) as a result of injection ice development. (4) Time series of terrain models highlighted the thaw-driven evolution of a borrow pit (6.4 × 105 m3 cut volume) constructed in permafrost terrain, whereby fluvial and thaw-driven sediment transfer (1.1 and 3.9 × 103 m3 a−1 respectively) was observed and annual slope profile reconfiguration was monitored to gain management insights concerning site stabilization. Elevation model vertical accuracies were also assessed as part of the case studies and ranged between 0.02 and 0.13 m Root Mean Square Error. Photogrammetric models processed with Post-processed Kinematic image solutions achieved similar accuracies without ground control points over much larger and complex areas than previously reported. The high resolution of UAV surveys, and the capacity to derive quantitative time series provides novel insights into permafrost processes that are otherwise challenging to study. The timely emergence of these tools bridges field-based research and applied studies with broad-scale remote-sensing approaches during a period when climate change is transforming permafrost environments. [ABSTRACT FROM AUTHOR]