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The Mackenzie River Delta (MRD) has been recognized as an important host of river‐derived wood deposits, and Mackenzie River wood has been found across the Arctic Ocean. Nevertheless, we lack estimates of the amount of carbon stored as wood and its age in the delta, representing a gap in carbon cycle estimates. Here, we use very high‐resolution satellite imagery and deep learning to map wood deposits in the MRD, combining this with field data to measure the stock and age of wood‐based carbon. We find >400,000 individual large wood deposits, collectively storing 3.1 × 1012 g‐C, equating to 2 × 106 g‐C ha−1 across the delta. Sampled wood pieces date from 690 AD to 2015 AD but are mostly young with ∼40% of the wood samples formed after 1955 AD. These estimates represent a minimum bound on an important surficial, potentially reactive, carbon pool compared to other deeper carbon stocks in permafrost zones. Plain Language Summary: The Arctic is warming rapidly, and this can increase landscape erosion. Consequently, carbon can be transferred into rivers and transported toward the Arctic Ocean. To date, work has tracked finer material dissolved in river water and the size of sand grains but has missed large pieces of wood that fall or slide into rivers. Wood is an important carbon‐rich material that may break down differently from the finer carbon pools, however, the amount of wood stored in Arctic river deltas has not been measured before. We also don't know the age of wood in those deposits. Here we study the Mackenzie River Delta, where river‐sourced wood is common and deposits extensive. We use very high‐resolution satellite images which show individual pieces of wood and use a machine learning technique to map wood across the delta. We also visited the deposits to measure their size and collected samples for radiocarbon dating. We find the wood is very young compared to other carbon pools carried by the river, and that the stocks of carbon are regionally important. Our work calls for further work to understand this overlooked carbon pool in river deltas and coastal regions of the Arctic. Key Points: We use remote sensing and deep learning to measure wood‐based carbon in an Arctic delta, filling an important gap in carbon cycle estimatesThe Mackenzie River Delta stores over 400,000 wood deposits in the delta totaling 3.1 × 1012 g‐CMeasured wood ages estimated from radiocarbon are younger than other river carbon pools, with ∼40% of the samples still growing after 1955 AD [ABSTRACT FROM AUTHOR]

Many geomorphologists who are mothers find it challenging to balance field research alongside pregnancy and caring for young children. We offer perspectives on the challenges to conducting fieldwork as mothers and possible solutions, as a means of promoting conversations and highlighting issues that are less commonly considered in field-based geomorphic research. Although every mother's experience and needs are different, we discuss strategies for conducting fieldwork, addressing childcare issues, and dealing with financial considerations. We call for our community to support geomorphologists who are pregnant or caring for young children in carrying out fieldwork to help enhance the diversity of voices and perspectives within our discipline. [ABSTRACT FROM AUTHOR]

Porosity, or void space, of large wood jams in stream systems has implications for estimating wood volumes and carbon storage, the impacts of jams on geomorphic and ecological processes, and instream habitat. Estimating porosity and jam dimensions (i.e. jam volume) in the field is a common method of measuring wood volume in jams. However, very few studies explicitly address the porosity values in jams, how porosity is calculated and assessed for accuracy, and the effect such estimates have on carbon and wood budgets in river corridors. We compare methods to estimate jam porosity and wood volume using field data from four different depositional environments in North America (jam types include small in‐channel jams, large channel‐margin jams, a large island apex jam, and a large coastal jam), and compare the results with previous studies. We find that visual estimates remain the most time‐efficient method for porosity estimation in the field, although they appear to underpredict back‐calculated porosity values; the accuracy of jam porosity, and thus wood volume, estimates are difficult to definitively measure. We also find that porosity appears to be scale invariant, dictated mostly by jam type, (which is influenced by depositional processes), rather than the size of the jam. Wood piece sorting and structural organization are likely the most influential properties on jam porosity, and these factors vary according to depositional environment. We provide a framework and conceptual model that uses these factors to demonstrate how modeled jam porosity values differ and give recommendations as a catalyst for future work on porosity of wood jams. We conclude that jam type and size and/or the study goals may dictate which porosity method is the most appropriate, and we call for greater transparency and reporting of porosity methods in future studies. © 2020 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The importance of large wood (LW) to riverine functions is well established scientifically and increasingly recognized by river managers in many countries. However, public perceptions largely associate LW with elevated danger and/or need for intervention. Such perspectives are amplified amongst recreational river users (defined here as any individuals that recreate by floating on the water surface of a river) who interact more directly with rivers than the general public and commonly view wood in life‐or‐death terms. Given that human life occupies a highest‐order charge for river managers, they are left in a difficult position when safety appears to conflict with environmental services. LW deficits are perpetuated partly because wood removal, often in the name of safety, is far easier than placing wood in rivers. Further, river restoration practitioners are frequently burdened with expectations and liability unparalleled in built environments. A fundamentally different mindset is necessary to achieve desired ecologic outcomes when working with rivers. Based on two decades of experience as boaters, LW practitioners, and emergency responders, we (1) discuss LW hazard and risk from recreational and management viewpoints, (2) discretize objective and measurable physical properties of LW hazards, and (3) propose a decision framework that implicitly addresses risk by considering LW hazards relative to river use and ambient hazards. The approach is structured to increase objectivity in LW hazard mitigation and diminish asymmetric biases that favor LW removal. Our intent is to build understanding and rational flexibility among risk‐averse management, regulatory, and funding entities to facilitate implementation of scientific understanding without undue risk to river users. © 2020 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Large wood (LW) jams are key riverine habitat features that affect hydraulic processes and aquatic habitat. The hydraulic influence of LW jams is poorly understood due to the complexity of fluid dynamics around irregular, porous structures. Here we validated a method for two‐dimensional hydraulic modeling of porous LW jams using the open‐source modeling software Delft3D‐FLOW. We sampled 19 LW jams at three reaches across the Columbia River Basin in the United States. We used computer‐generated porous plates to represent LW jams in the modeling software and calibrated our modeling method by comparing model outputs to measured depths and velocities at validation points. We found that modeling outputs are error‐prone when LW jams are not represented. By representing LW jams as porous plates we reduced average velocity root mean square error (RMSE) values (i.e., improved model accuracy) by 42.8% and reduced average depth RMSE values by 5.2%. These differences impacted habitat suitability index modeling. We found a 15.1% increase in weighted useable area for juvenile steelhead at one test site when LW jams were simulated vs. when they were ignored. We investigated patterns in average RMSE improvements with varying jam size, bankfull obstruction, porosity, and structure type, and river complexity. We also identified research gaps related to field estimation of LW jam porosity and porous structure modeling methods. Research Impact Statement: Hydraulic models are error‐prone where rivers interact with large wood jams. Our method for representing wood jams improves hydraulic model accuracy and ecohydraulic analysis. [ABSTRACT FROM AUTHOR]

This study presents a case study of large wood transport on the great Slave River in northern Canada with the objective to better understand the processes of and variability in pulsed wood fluxes from large forested catchments. We use a varied approach, integrating field characterization of wood, historical anecdotes, repeat aerial imagery of stored wood, and time-lapse imagery of moving wood, for a robust analysis and synthesis of processes behind pulsed wood flux, from yearly uncongested export to rare congested wood floods. Repeat monitoring of known sites of temporary storage with new or historic imagery proved to be a very useful tool for constraining wood flux histories. Pulsed wood export on the Slave River is not an artifact of episodic recruitment from major up-basin disturbances, but rather reflects decadal- to half-century-scale discharge patterns that redistribute wood recruited from channel migration and bank slumping. We suggest that the multiyear flow history is of paramount importance for estimating wood flux magnitude, followed in declining importance by the yearly sequence of peaks and the magnitude and characteristics of the rising limb of individual floods. [ABSTRACT FROM AUTHOR]

ABSTRACT Monitoring large wood (LW: width > 10 cm, length > 1 m) in transport within rivers is a necessary next step in the development and refinement of wood budgets and is essential to a better understanding of basin-wide controls and patterns of LW flux and loads. Monitoring LW transport with coarse interval (≥ 1 min) time-lapse photography enables the deployment of monitoring cameras at large spatial and long temporal scales. Although less precise than continuous sampling with video, it allows investigators to answer broad questions about basin connectivity, compare drainages and years,and identify transport relationships and thresholds. This paper describes methods to: (i) construct fluvial wood flux curves; (ii) analyze the effects of sample interval lengths on transport estimates; and (iii) estimate total wood loads within a specified time period using coarse-interval time-lapse photography. Applying these methods to the Slave River, a large-volume (103 m3 s-1), low-gradient (10− 2 m km− 1) river in the subarctic (60∘ N), yielded the following results. A threshold relationship for wood mobility was located around 4500 m3 s-1. More wood is transported on the rising limb of the hydrograph because wood flux declines rapidly on the falling limb. Five- and ten-minute sampling intervals provided unbiased equal variance estimates of 1 min sampling, whereas 15 min intervals were biased towards underestimation by 5-6%, possibly due to periodicity in wood flux. Total LW loads estimated from the 1 min dataset and adjusted for a 15% misdetection rate from 13 July to 13 August are: 1600 ± 200 # pieces, 600 ± 200 m3 and of the order of 1.3 × 105 kg carbon. The total wood load for the entire summer season is probably at least double this estimate because only the second half of the summer was monitored and a large early summer peak freshet was missed. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Instream and floodplain wood can provide many benefits to river ecosystems, but can also create hazards for inhabitants, infrastructure, property, and recreational users in the river corridor. We propose a decision process for managing large wood, and particularly for assessing the relative benefits and hazards associated with individual wood pieces and with accumulations of wood. This process can be applied at varying levels of effort, from a relatively cursory visual assessment to more detailed numerical modeling. Decisions to retain, remove, or modify wood in a channel or on a floodplain are highly dependent on the specific context: the same piece of wood that might require removal in a highly urbanized setting may provide sufficient benefits to justify retention in a natural area or lower-risk urban setting. The proposed decision process outlined here can be used by individuals with diverse technical backgrounds and in a range of urban to natural river reaches so that opportunities for wood retention or enhancement are increased. [ABSTRACT FROM AUTHOR]