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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]

In the warming Arctic, retrogressive thaw slumping (RTS) has emerged as the primary thermokarst modifier of icerich permafrost slopes, raising urgency to investigate the distribution and intensification of disturbances and to determine trajectories of landscape evolution and the cascade of effects. Tracking RTS is challenging due to constraints of remote sensing products and a narrow understanding of 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 8 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) was required to characterize the diverse range of disturbance morphologies and activity levels, which provided temporally consistent information on thaw slump affected slopes and attributes. The MSI delineation of three high-resolution hillshade DEMs (airborne stereo-imagery, LiDAR, ArcticDEM) revealed temporal and spatial trends in these multi-year, chronic mass-wasting features. For example, in the Tuktoyaktuk Coastal Plains, a +38% increase in active RTS and +69% increase in total active surface area were observed between 2004 and 2016. However, the total area of RTS did not change considerably (+3.5%) because the vast majority of active thaw slumping processes have occurred in association with past disturbances. Interpretation of thaw-driven change is thus dependent on how active RTS are defined to support disturbance inventories. 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 scale (adj-R2 of 0.85, n=1,522), but also revealed that elongated, shoreline RTS reflects outliers poorly represented by the modelling. 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 change in the planimetric area. Observations further suggested variation in depth-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. [ABSTRACT FROM AUTHOR]

In the last 30 years, work on large wood (LW) has expanded and matured considerably, and river scientists, managers and practitioners now have a better appreciation of the role of LW in maintaining ecosystems, forming or stabilizing riverine landforms, and interacting with river morphodynamics. We have gained a better understanding of the hazards posed by the recruitment and transport of LW in the river channel and associated infrastructure. While LW dynamics have traditionally been studied in the natural river environment, innovations in laboratory techniques have enabled important advances in understanding LW process dynamics, using physical scale models, new sensors, scanners and sophisticated model boundary conditions. Current trends in LW laboratory research focus on (1) mobilization and transport of logs, (2) trapping and deposition of sediment in the presence of LW and (3) LW contribution to hydraulic flow resistance. Ultimately, a combined process understanding is needed to assess impacts upon infrastructure with erodible boundaries, such as bridge piers and LW retention racks. In this review, we present a critical analysis of emerging experimental work on LW obtained through physical modelling studies. We put recent experimental work in context with global LW management challenges. In particular, we set our work in context with the present environmental and engineering issues that confront catchment and natural resource managers in Switzerland and New Zealand. We show how improved physical models incorporating LW transport, accumulation and scouring processes are needed to contribute to more reliable hazard and risk assessment and improved river management in LW‐prone systems. [ABSTRACT FROM AUTHOR]