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Logjams create diverse physical and ecological effects in stream channels, including at least temporary storage of water, sediment, and particulate organic matter. We hypothesize that logjams that span the entire bankfull channel width in channels ≤25 m wide are more effective in storing these materials than non‐channel spanning logjams. We test this hypothesis by systematically comparing characteristics of 183 logjams from 17 stream reaches in the Southern Rocky Mountains. Our data set is novel in that it evaluates naturally occurring logjams in unaltered streams in a single study area specifically based on whether they span the stream channel. We find that channel‐spanning logjams have a significantly larger number of wood pieces, longer & wider pieces, more ramp and bridge pieces, and greater logjam height and volume, both as raw data and when standardized by average channel width. Channel‐spanning logjams also have significantly greater backwater pool volume and volume of particulate organic matter stored in backwater pools and in logjams. Restoration employing engineered logjams in relatively small channels currently focuses on non‐spanning logjams, but could be expanded to include spanning logjams. Plain Language Summary: Logjams are accumulations of three or more large wood pieces in streams and stream environments. Logjams can obstruct flow and create frictional resistance in small stream channels, creating many physical and beneficial ecological effects in stream environments. This includes, but is not limited to, temporary storage of water, sediment, and organic matter, which translates to habitat and nutrient availability for aquatic organisms. Despite these benefits, deforestation and active wood removal from stream environments have significantly reduced the size and abundance of logjams throughout the temperate latitudes, contributing to the loss of ecological integrity and the simplification of stream channels. Stream restoration projects are increasingly using engineered logjams (ELJs), which are less likely to span a stream channel than naturally occurring logjams. Limited understanding of how logjam characteristics relate to specific effects constrains our ability to evaluate whether ELJs have comparable effects to natural logjams. We systematically evaluate characteristics and effects of 183 logjams in unaltered headwater Southern Rocky Mountain streams. We find that channel‐spanning logjams have significantly greater effects, such as pool and organic matter volume storage, than non‐channel‐spanning logjams, and recommend considering channel‐spanning ELJs in restoration projects in small streams to maximize retention. Key Points: Logjams that span the bankfull channel create significantly greater storage of water and organic matter than non‐spanning logjamsChannel‐spanning logjams also have significantly more wood, larger pieces of wood, and more ramp and bridge wood piecesStream rehabilitation projects employing engineered logjams should consider channel‐spanning logjams to achieve greater retention [ABSTRACT FROM AUTHOR]

The increase of geomorphological research during the last decades in the Gorce Mts. caused the need for state-of-art review papers. The Gorce Mountains were formed as an isolated massif with Mt Turbacz (1310 m a.s.l.) as the highest summit. River channels are remodeled by sudden and high-level floods with the critical impact of log jams. The main processes influencing hillslope relief were landsliding, run-off, and tree uprooting. The review suggests the following issues await for studies: a long-term landscape evolution, monitoring of morphogenetic processes, and origin of landslides with their contribution to denudation rates. Also, current biomorphodynamics (uprooting process) has not been sufficiently studied. [ABSTRACT FROM AUTHOR]

This article seeks to explain the increasingly regressive (or illiberal) behaviour on the part of the Indonesian military. It focuses on the expansion of the Army's Territorial Command structure, the growing military intrusion into civilian polity and the stunted progress of military professionalism. It provides an organisational, rather than political, perspective. Conceptually, the article synthesises various approaches to comparative politics to explain why and how military personnel policies affect political behaviour. Empirically, using a series of original datasets of hundreds of officers, the article demonstrates how promotional logjams – too many officers but too few positions available – over the past decade help explain the regressive behaviours we recently witnessed. It is further argued that the lack of institutionalisation in personnel policies gave rise to and prolonged these logjams. This article draws attention to the importance of intra-organisational dynamics in understanding the state of civil–military relations in post-authoritarian Indonesia. [ABSTRACT FROM AUTHOR]

In cooperation with large instream wood (LW) within logjams, small instream wood (SW) can control downstream flux of sediment and particulate organic matter and can play an important role for stream ecosystems. However, information regarding the density and moisture content of SW—which affects wood transport, wood decay, and mass loading—is limited. Here we investigated the SW properties, i.e., density under field conditions ( in situ density), basic density, volumetric water content, and depositional environment of SW sampled from five logjams and their backwater areas in two headwater streams (second- and third-order streams) surrounded by mixed broadleaf-conifer forests in western Japan. The in situ density ranged from 0.49 to 1.25 g cm − 3 , and pieces with densities > 1.0 g cm − 3 accounted for 45% of all samples. Additionally, the in situ density of SW closely related to the volumetric water content ( r 2 = 0.76) rather than the basic density as an index of solidity or decay condition of wood. The SW that was partially submerged in water had a higher volumetric water content than SW exposed to air. These results indicate that a nonfloating transport cannot be ignored as an important mechanism for SW movement and that in situ density depends not on the solidity of the wood but on water sorption by SW. However, waterlogged SW should be well decayed because it has a lower basic density than air-exposed and sediment-buried SW. We conclude that the moisture conditions of the depositional environment can affect subsequent transport and decay processes of SW. Moreover, most waterlogged and sediment-buried SW, because of its high in situ density (> 1.0 g cm − 3 ), may contribute to clogging between the channel bed and LW that initiate a logjam during future movements. [ABSTRACT FROM AUTHOR]

This paper investigates the dynamics of logjam-induced floods and alluvial deposition in the Bolivian Amazon and the effects these have on forest disturbance and recovery cycles. It expands on previous work by Gullison et al. (1996) who reported a case of catastrophic floods triggered by logjams in the Chimane Forest in the Bolivian Amazon. No further studies have followed up on this observation and no research has been published on the effects of large wood in tropical lowland rivers. The study is based on the analysis of a time series of Landsat imagery (1984-2016) and field evidence. Results show that logjam-induced floods are a major driver of forest disturbance along the Andean piedmont in the Bolivian Amazon. New logjams form on an almost yearly basis, always further upriver, until an avulsion takes place. Logjam-induced floods are characterized here by the sudden deposition of a thick sand layer and the death of forest in a V-shaped area. The Bolivian Amazon offers a unique opportunity for further research on how large wood affects river behavior in lowland tropical settings and how large and frequent forest disturbance events resulting from river logjams affect forest biodiversity and community successions. [ABSTRACT FROM AUTHOR]

Large wood in rivers and logjams are linked to the presence of varied riverine morphologies and increased abundance and diversity of aquatic biota. Current research into the ecohydrological, morphological and geochemical effects of logjams is restricted by difficulties in comparing findings between river systems. The problem is exacerbated by a lack of standardized metrics for recording and reporting logjams and a scale dependence of logjam effects with river size. In this paper, a new method for analysing logjams is presented based on a set of seven dimensionless metrics of structure and morphological effects. These metrics are used along with a cluster analysis to identify key logjam types within a study river. The analysis framework is applied to data from a small forest river in the UK and identifies that 73% of logjams in this system can be grouped into eight distinct classes. Of these classes, two are logjams that only partly fill the channel, and six are channel spanning. The individual classes are differentiated from each other principally by the degree of lateral and vertical erosions found in association with the logjams. The dimensionless metrics are also applied qualitatively to a range of logjams described in the literature and show the potential for the method to be applied as a standard survey and analysis framework for logjams across diverse river environments. The potential to link logjam form with function, and therefore provision of specific habitats, has wide applicability to the design and monitoring of river restoration schemes. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Human interventions that limit channel mobility such as bank stabilization are frequent in riparian zones in urban or agricultural environments. This is potentially problematic because channel mobility is an important geomorphological and ecological agent that structures natural instream and riparian ecosystems. This study aims to (1) quantify the relationship between mobility and three types of habitat-related features, namely bars, oxbow lakes and log jams, for a 54-km-long reach of the Yamaska Sud-Est River (Quebec, Canada), which runs from the forested Appalachian Mountains to the agricultural St-Lawrence lowlands, and (2) evaluate the impact of human interventions and geomorphological characteristics on these three features. Channel mobility was measured from historical aerial photos for the period 1950-2009. A combination of high-resolution aerial photos, LiDAR digital elevation model, and field observations was used to measure and map sediment bars, oxbow lakes and log jams, as well as several geomorphological characteristics (channel width, slope, sinuosity and floodplain width). A strong link between the mobility and the presence of habitat features is revealed, but local geomorphological contexts result in different mobility patterns responsible for specific habitats. Floodplain to channel width ratio appears as the best geomorphological factor predicting habitat diversity. Human intervention, mostly through bank stabilization, also appears to be a key factor limiting mobility and its related habitats. These results highlight the importance of defining a protected mobility corridor along rivers where geomorphic processes such as bank erosion can freely occur, as it is an essential process that should be integrated in land use planning and river management. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A federal, state, and private partnership leveraged resources and employed a long-term, systematic approach to improve aquatic habitat degraded by decades of intensive forest management in Finney Creek, a tributary to the Skagit River of Northwest Washington State. After more than a decade of work to reduce sediment sources and the risk of landslides within the watershed, log jam installation commenced in 1999 and progressed downstream through 2010. Log jam design was adapted as experience was gained. A total of 181 log jams, including 60 floating log ballasted jams, were constructed along 12 km of channel. The goal was to alter hydraulic processes that affect aquatic habitat formation along 39 km of stream with emphasis on 18.5 km of lower Finney Creek. Aquatic habitat surveys over a five-year period show an increase in the area of large pools and an accompanying increase in residual and maximum pool depth in the lower river reach. Channel cross sections show a generally deeper channel at the log jams, better channel definition in the gravel deposits at the head of the log jams, and improved riffle and thalweg development below the log jams. Stream temperature in the upper river decreased by 1.0°F in the first three years, and 1.1°F in the lowest treated reach over nine years. There is a trend of less stream heating over the restoration time period. Photo points show that riparian vegetation is recolonizing gravel bars. [ABSTRACT FROM AUTHOR]

Abstract: A localized sandstone split in the Mary Lee coal (Early Pennsylvanian, Langsettian) of the Black Warrior Basin, Alabama, has a channel-form geometry and preserves a concentrated log-and-gravel (pebbles, cobbles, and boulders) assemblage at the top of the fill sequence. Gravel lithotypes within and amongst rooting structures of lycopsid, cordaitean, and calamitean trees are indicative of an Appalachian orogenic provenance, and support an allochthonous origin for some of the logs. In addition, a Skolithos ichnological assemblage within the channel is indicative of opportunist colonization during channel fill. A low sinuosity geometry characterizes the overall channel-form belt, exhibiting a general northwesterly trend. Paleocurrent measurements from the cross-bedded sandstone at the margin of the channel belt indicate flow was to the northwest. Log orientations at these sites are subperpendicular to perpendicular to the overall sediment transport direction and are interpreted to represent an ancient log jam. The genesis of the fluvial channel, the introduction and emplacement of the concentrated log assemblage, the effects of this floating log accumulation on sedimentation within the channel, and the relationship between paleocurrent and log orientation are discussed. The Red River, located in the southern United States, is used as a modern analog for comparative purposes. [Copyright &y& Elsevier]

Investigates the influence of debris-flow deposits and log jams on the location of pools and alluvial channel in Oregon. Differences in the type and location of log jams; Role of drainage area on the distribution of bedrock and alluvial; Contrast between old-growth and industrial forest.