Quantification of fluvial wood using UAVs and structure from motion

Sanhueza, Daniel; Picco, Lorenzo; Ruíz-Villanueva, Virginia; Iroumé, Andrés; Ulloa, Héctor; Barrientos, Guillermo

doi:10.1016/j.geomorph.2019.106837

Cited by 44 publications

(55 citation statements)

References 66 publications

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“…unless otherwise indicated, but rarely do studies report α, the percentage of the jam that is solid, but not wood ( Figure 1A). Time consuming to determine WV; not possible for some field situations Manners et al, 2007;Sanhueza et al, 2019;Thevenet et al, 1998; Visual Visual estimate of proportion of void space (or proportion of filled space subtracted from unity) of jam Best guess, difficult to replicate; internal and/or submerged portion of jams nearly impossible to see and characterize Steeb et al, 2017;Ventres-Pake et al, 2019 Stratigraphic characterization Estimate porosity in measured vertical and/or horizonal layers (either visual estimation or back-calculation of plot or segment); porosity estimates weighted to get a porosity estimate for entire jam Direct measurement Measure all LW pieces through deconstruction or in situ and use equation for cylinder to convert to WV; or weigh all pieces and use wood density estimates to convert to WV Time consuming; often only focuses on LW and smaller material either visually estimated or ignored; assumption of cylindrical shape introduces inaccuracy Livers and Wohl, 2016;Manners et al, 2007;Ravazzolo et al, 2015;Sanhueza et al, 2019;Thevenet et al, 1998 Complete box JV completely encloses all wood, organic matter, and void space; 0.9 porosity used to convert air-wood space (JV) to WV with Equation 1 or Equation 2; Figure 1(B) A 0.9 porosity specific to Thevenet et al, 1998; calibration curves needed to account for variability in LW density and jam types across regions or depositional processes Boivin et al, 2015;Thevenet et al, 1998 Best-fit box JV defined by a box, prism, or other simple geometric shape that best fits the jam but may not totally enclose all jam materials; convert to WV; JV is subjective; pieces extending outside best-fit box must be accounted for appropriately to obtain total WV Dixon, 2016;…”

Section: Terminology and Basic Equations Usedmentioning

confidence: 99%

“…Recent efforts characterize jams as the volume within a mold of the outside of the jam rather than a box or easily surveyed shape, usually computed from three-dimensional (3D) representations of the jam generated from complete field surveys of the outside geometry of jams ( Figure 1D). Increasingly popular is the use of structure-from-motion (SfM) and unmanned aerial vehicles (UAVs) to generate high-resolution orthomosaics (Sanhueza et al, 2019) or dense and 3D meshes and point clouds (Spreitzer et al, 2019) that capture the detailed complexity of the external surface of the jam. However, these still need to be adjusted by a porosity value to derive WV (Equation 1) since the center of the jam is still obscured, and the more detailed representation of the outside surface, the lower the porosity value should be (Spreitzer et al, 2019).…”

Section: Porosity Problemsmentioning

confidence: 99%

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Porosity problems: Comparing and reviewing methods for estimating porosity and volume of wood jams in the field

Livers

Lininger

Kramer

et al. 2020

Earth Surf Processes Landf

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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.

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Section: Terminology and Basic Equations Usedmentioning

confidence: 99%

Section: Porosity Problemsmentioning

confidence: 99%

Porosity problems: Comparing and reviewing methods for estimating porosity and volume of wood jams in the field

Livers

Lininger

Kramer

et al. 2020

Earth Surf Processes Landf

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“…By the 21st century, however, research on large wood in rivers and the ecology of disturbed landscapes had matured to the point that the eruptions of Chilean volcanoes (Chaiten in 2008 and Calbuco in 2015) prompted intensive research on large wood. This work by an international cadre of scientists has concentrated on channel segments of the Blanco (also known as Chaitén) and Rayas rivers in the Chaitén area, and the Blanco‐Este River which drains the northeastern flanks of Calbuco volcano (Umazano et al ., 2014; Valdebenito et al ., 2015; Ulloa et al ., 2015a, 2015b; Mohr et al ., 2017; Tonon et al ., 2017; Sanhueza et al ., 2019). The studies address a variety of questions concerning sources and fates of large wood affected by pyroclastic density currents (PDC), tephra fall, and post‐eruption runoff processes in rivers draining from these volcanoes.…”

Section: Case Studiesmentioning

confidence: 99%

Reflections on the history of research on large wood in rivers

Swanson

Gregory

Iroumé

et al. 2020

Earth Surf Processes Landf

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Dynamics and functions of large wood have become integral considerations in the science and management of river systems. Study of large wood in rivers took place as monitoring of fish response to wooden structures placed in rivers in the central United States in the early 20th century, but did not begin in earnest until the 1970s. Research has increased in intensity and thematic scope ever since. A wide range of factors has prompted these research efforts, including basic understanding of stream systems, protection and restoration of aquatic ecosystems, and environmental hazards in mountain environments. Research and management have adopted perspectives from ecology, geomorphology, and engineering, using observational, experimental, and modelling approaches. Important advances have been made where practical information needs converge with institutional and science leadership capacities to undertake multi‐pronged research programmes. Case studies include ecosystem research to inform regulations for forest management; storage and transport of large wood as a component in global carbon dynamics; and the role of wood transport in environmental hazards in mountain regions, including areas affected by severe landscape disturbances, such as volcanic eruptions. As the field of research has advanced, influences of large wood on river structures and processes have been merged with understanding of streamflow and sediment regimes, so river form and function are now viewed as involving the tripartite system of water, sediment, and wood. A growing community of researchers and river managers is extending understanding of large wood in rivers to climatic, forest, landform, and social contexts not previously investigated. © 2020 John Wiley & Sons, Ltd.

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“…However, such technology is expensive and therefore available only in some regions. Alternatively, photogrammetry based on structure from motion multi-view stereo (SfM-MVS) using UAV (uncrewed aerial vehicle) has been proven time-e cient compared to classical eld surveys (Sanhueza et al, 2019). This approach overcomes data availability issues and is relatively low-cost.…”

Section: Introductionmentioning

confidence: 99%

“…This approach overcomes data availability issues and is relatively low-cost. Nevertheless, most tests were conducted in low-land and ood plains rather than lowaccessibility areas such as steep channels (e.g., Sanhueza et al, 2019). As the accuracy of SfM-MVS is remarkably in uenced by complex surfaces and obstacles, such as steep slopes, large reliefs, and vegetation coverage (e.g., Fonstad et al, 2013; James and Robson, 2014), many unresolved uncertainties remain over the application of the SfM-MVS approach in steep and complex targets, such as woody debris in channels.…”

Section: Introductionmentioning

confidence: 99%

Comparison of Length and Transport of Entrapped Woody Debris in Coniferous and Broadleaf Forests Based on Mapping Using Ortho-Photographs Acquired by Uncrewed Aerial Vehicle

Tsunetaka¹,

Mtibaa²,

Asano³

et al. 2020

Preprint

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Landslides and debris flows often result in woody debris from initiation and riparian zones, through their runout. Considering that woody debris is one of the main components of watershed ecosystems, the importance of quantifying its properties and transport is evident. However, the low accessibility of disturbed channels after landslides and debris flows generally impedes the accurate and quick investigation of woody debris. The recent advances in photogrammetry techniques and technology may overcome such issues. In this study, we used ortho-photographs acquired by a small uncrewed aerial vehicle (UAV) for measuring the lengths of woody debris entrapped mainly by closed-type check-dams. We focused on two channels, located in coniferous and broadleaf forests and affected by two different landslides events. The measurement accuracy was analyzed by comparing the lengths derived from the UAV method with direct measurements. When both edges of woody debris were satisfactorily extracted from an ortho-photograph acquired via UAV, the length of the woody debris with respect to coniferous trees can be measured with an accuracy of approximately ±0.5 m. However, some coniferous trees were captured by stand trees in the riparian zone, and the coverage by tree-crowns led to the underestimation by several meters of the extracted length of the entrapped woody debris. For broadleaf trees, most of the extracted lengths were shorter than the directly measured lengths. This is probably caused by the low visibility of both edges due to the complex structures of the root-wad and the tree-crown. Our results showed that there were no significant changes in the lengths and locations of the entrapped woody debris, in both sites, after seven months of the first UAV flight. In the coniferous forests, the rainfall that triggered landslides in 2017 exceeded the 100-year return level, which was obviously an abnormal intense rainfall. Although the 2019 rainfall event that occurred between UAV flights was not as much to the rainfall triggering landslides, rainfall intensities with different durations reached the second-highest value from 1976 to 2019, exceeding the 30-years return period. This suggests that most of the entrapped woody debris rarely migrate even under extreme rainfall.

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Quantification of fluvial wood using UAVs and structure from motion

Cited by 44 publications

References 66 publications

Porosity problems: Comparing and reviewing methods for estimating porosity and volume of wood jams in the field

Porosity problems: Comparing and reviewing methods for estimating porosity and volume of wood jams in the field

Reflections on the history of research on large wood in rivers

Comparison of Length and Transport of Entrapped Woody Debris in Coniferous and Broadleaf Forests Based on Mapping Using Ortho-Photographs Acquired by Uncrewed Aerial Vehicle

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Quantification of fluvial wood using UAVs and structure from motion

Cited by 44 publications

References 66 publications

Porosity problems: Comparing and reviewing methods for estimating porosity and volume of wood jams in the field

Porosity problems: Comparing and reviewing methods for estimating porosity and volume of wood jams in the field

Reflections on the history of research on large wood in rivers

Comparison of Length and Transport&nbsp;of Entrapped Woody Debris in Coniferous and Broadleaf Forests Based on Mapping Using Ortho-Photographs Acquired by&nbsp;Uncrewed Aerial Vehicle

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Comparison of Length and Transport of Entrapped Woody Debris in Coniferous and Broadleaf Forests Based on Mapping Using Ortho-Photographs Acquired by Uncrewed Aerial Vehicle