scholarly journals Theoretical Investigation of Equilibrium Dynamics in Braided Gravel Beds for the Preservation of a Sustainable Fluvial Environment

2021 ◽  
Vol 13 (3) ◽  
pp. 1246
Author(s):  
Marilena Pannone ◽  
Annamaria De Vincenzo
Keyword(s):  
Gradual Transition ◽  
Stream Power ◽  
Higher Plant ◽  
Gravel Beds ◽  
Ground Flora ◽  
Braided Rivers ◽  
Dimensionless Unit ◽  
Subsurface Waters ◽  
Gravel Bars ◽  
Transverse Channel

Gravel bars have an important role in the exchange between surface and subsurface waters, in preventing and mitigating riverbank erosion, in allowing the recreational use of rivers, and in preserving fluvial or riparian habitats for species of fishes, invertebrates, plants, and birds. In many cases, gravel bars constitute an important substrate for the establishment and development of ground flora and woody vegetation and guarantee higher plant diversity. A sustainable management of braided rivers should, therefore, ensure their ecological potential and biodiversity by preserving a suitable braiding structure over time. In the present study, we propose an analytical–numerical model for predicting the evolution of gravel bars in conditions of dynamical equilibrium. The model is based on the combination of sediment balance equation and a regression formula relating dimensionless unit bedload rate and stream power. The results highlight the dependence of the evolving sediment particles’ pattern on the ratio of initial macro-bedforms longitudinal dimension to river width, which determines the gradual transition from advective and highly braiding to diffusive transport regime. Specifically, the tendency to maintain braiding and flow bifurcation is associated with equilibrium average bed profiles and, therefore, equilibrium average stream power characterized by the maximum period that does not exceed transverse channel dimension.

scholarly journals Hydrogeomorphic effects on bedload scour in bull char (Salvelinus confluentus) spawning habitat, western Washington, USA

2010 ◽  
Vol 67 (4) ◽  
pp. 626-640 ◽  
Author(s):  
Jeffrey G. Shellberg ◽  
Susan M. Bolton ◽  
David R. Montgomery
Keyword(s):  
Woody Debris ◽  
Main Channel ◽  
Spawning Habitat ◽  
Stream Power ◽  
Salvelinus Confluentus ◽  
Channel Change ◽  
Gravel Beds ◽  
Side Channels ◽  
Western Washington ◽  
Sand And Gravel

We investigated the vulnerability of fall-spawned bull char ( Salvelinus confluentus ) embryos to redd scour during winter rain and rain-on-snow flood discharges in western Washington, USA. It was hypothesized that the magnitude of bedload scour at bull char redds is reduced by the provision and selection of stable refugia habitat controlled by local-, reach-, or subcatchment-scale variables such as hydraulic habitat unit and channel type. Bedload scour and channel change were measured using 96 scour monitors and 34 elevational transects in three catchments over 2 to 4 years. Scour to cited egg burial depths of bull char did not commence until discharge typically exceeded the 2-year recurrence interval. At a local scale, scour varied significantly among side channel, protected main channel, and unprotected main channel redd sites. Unprotected gravel patches in simplified channel types with moderate gradients were most susceptible to deep scour, especially if coupled with the transient supply and storage of sand and gravel from mass wasting. Partially transport-limited reaches had reduced scour due to lower stream power and armored gravel beds. Complex spawning habitat (i.e., with abundant large woody debris and side channels) was important in providing refuge from deep scour and in buffering embryos against inhospitable hydrologic or sediment regimes.

Habitat use as a predictor of nest raiding by individual hedgehogs Erinaceus europaeus in New Zealand

2006 ◽  
Vol 12 (3) ◽  
pp. 180 ◽  
Author(s):  
Christopher Jones ◽  
Grant Norbury
Keyword(s):  
Breeding Season ◽  
Implicit Assumption ◽  
Pitfall Trapping ◽  
Night Time ◽  
Erinaceus Europaeus ◽  
Gravel Beds ◽  
Braided Rivers ◽  
Nest Protection ◽  
Bird Breeding ◽  
Central South

Predation by introduced hedgehogs Erinaceus europaeus is a significant cause of nest failure in threatened endemic wading birds nesting on the dry gravel beds of braided rivers in New Zealand's central South Island. Night-time movements of 10 hedgehogs (four male; six female) were investigated during the 2002 bird breeding season using spool-and-line tracking and GPS data recording. Nine of the 10 hedgehogs studied used river braids rarely and concentrated their activity in scrub and woodland habitat. One female foraged almost exclusively on the dry river braids. The ranked order of habitat preference (scrub>woodland>river braid) matched the ranked availability of hedgehogs' most common invertebrate prey, estimated by pitfall trapping, in the three habitat types. Male foraging ranges were generally larger than those of females, except for the female that foraged on the relatively resource-poor river braids, which had the second largest range overall. This animal had a much higher probability of encountering, and opportunistically raiding, nests than the others. Trapping programmes targetted at nuisance predators commonly aim to reduce overall predator abundances within a designated area using traps set along logistically convenient lines. This design reflects the implicit assumption that all target animals within the area represent an equal risk to threatened prey. Our results suggest that this assumption may not always be valid. To improve nest protection during the birds' breeding season, we suggest that traps should be focussed in and around the nesting habitat in order to target those predators that habitually forage in the area.

The case of the braided river that meandered: Bar assemblages as a mechanism for meandering along the pervasively braided Missouri River, USA

2020 ◽  
Author(s):  
John M. Holbrook ◽  
Sarah D. Allen
Keyword(s):  
Missouri River ◽  
Braided River ◽  
Stream Power ◽  
Meandering Rivers ◽  
Meandering River ◽  
Braided Rivers ◽  
Single Thread ◽  
Point Bars ◽  
Meander Bends ◽  
Exclusive Processes

This paper offers a mechanism for meandering in an otherwise braided river and then discusses its general implications for river processes and fluvial deposits. Braided rivers manage to meander without the paired point bars and single-thread channels that are instrumental in developing bends in other meandering rivers. The driving processes for meandering in these braided systems remain enigmatic. The unchannelized and prechannelized Missouri River is an example of a braided meandering river, and it provides an opportunity to gain insight into these processes. This study utilized historical maps, sequential air photos, and surficial geologic maps both to define the processes by which this braided river meanders, and to characterize the deposits produced by these processes. These data show that the Missouri River meanders by building point assemblages instead of point bars. Repeated accretion of midchannel and lateral bars to a common point on the bank forces development of a meander bend around a point assemblage comprising multiple amalgamated compound bars. This differs from single-thread systems, which expand and translate bends around a single compound point bar. Alternating development of point assemblages forces meandering over successions of meander bends. Braided meander loops grow by expansion and translation like single-thread rivers, but they also may contract to produce counterpoint assemblages. Contraction appears to be the more common means of loop abandonment compared to loop cutoff for the braided Missouri River. This differs from single-thread meandering rivers, where contraction is limited, and loop cutoff is consistently the dominant abandonment process. Deposits of the braided meandering Missouri River differ from deposits of single-thread rivers in the rarity of both meander scrolls and single-thread channel fills. Instead, point and counterpoint assemblages comprise fusiform bar elements bound by small filled remnants of anabranch channels. These assemblages are commonly bound by meander cutbank scars. Cutbank scars associated with contraction, however, tend to be composite rather than discrete erosional surfaces, and they do not tend to bind river-scale abandoned channel fills. The braided meandering Missouri River also differs from wandering rivers because wandering rivers meander by building compound bars instead of assemblages, are more gravelly, have less pervasive and much less mobile midchannel bars, and appear to reflect a transitional intermediate pattern instead of a stable hybrid pattern. Braiding and meandering both expend stream power, and both are mechanisms for achieving channel equilibrium. The Missouri River exhibits both of these processes in tandem; thus, meandering and braiding are not mutually exclusive processes. Braided meandering rivers like the Missouri River are less common than either straight-braided or single-thread-meandering rivers, but they are not unique. The long-held distinction of braided versus meandering patterns for rivers thus may be practical but is not definitive.

Characterization of an iron-containing superoxide dismutase from a higher plant, Citrus limonum

1994 ◽  
Vol 90 (2) ◽  
pp. 339-347 ◽  
Author(s):  
Maria S. Almansa ◽  
Luis A. del Rio ◽  
Francisca Sevilla
Keyword(s):  
Superoxide Dismutase ◽  
Higher Plant ◽  
Citrus Limonum

In the Shadow of Violence: Lessons for Limited Access Societies

2012 ◽  
pp. 4-31 ◽  
Author(s):  
D. North ◽  
J. Wallis ◽  
S. Webb ◽  
B. Weingast
Keyword(s):  
Developing Countries ◽  
Economic Development ◽  
Open Access ◽  
Political Stability ◽  
Gradual Transition ◽  
Major Conclusion ◽  
Economic Competition ◽  
Limited Access ◽  
Forthcoming Book ◽  
Personal Connections

The paper presents a summary of the forthcoming book by the authors and discusses the sample study of the 9 developing countries. While admitting the non-linearity of economic development they claim that the developing countries make a transition from the limited access orders (where the coalition of powerful elite groups plays a major role, that is based on personal connections and hampers free political and economic competition) to the open access orders with democratic government and efficient decentralized economic system. The major conclusion of this article is that what the limited access societies should do is not simply introducing open access institutions, but reorganizing the incentives of the elites so that to limit violence, provide economic and political stability and make a gradual transition to the open access order beneficial for the elites.

Singapore in 1982: Gradual Transition to a New Order

Asian Survey ◽  
1983 ◽  
Vol 23 (2) ◽  
pp. 201-207
Author(s):  
Chan Heng Chee
Keyword(s):  
Gradual Transition ◽  
New Order

Diagnostics of Track Infrastructure as Part of the Digitisation of Russian Railways

2020 ◽  
Vol 64 (188) ◽  
pp. 149-160
Author(s):  
Janusz Poliński
Keyword(s):  
Diagnostic Tools ◽  
Gradual Transition ◽  
Technical Diagnostics ◽  
Strategic Development ◽  
Railway Infrastructure ◽  
Monitoring And Forecasting ◽  
Infrastructure Maintenance ◽  
Result Analysis ◽  
Railway Maintenance ◽  
Condition Diagnosis

Technical diagnostics is an integral part of the railway maintenance process. Through timely maintenance, in addition to ensuring the safety, functional and technical reliability of the infrastructure, maintenance costs are reduced and downtime losses, due to failures or premature repair requests, are eliminated or reduced. The track infrastructure diagnostic tools have evolved. This is related to, among others, the miniaturisation of instruments, reading accuracy during motion, as well as upgraded measurement automation and result analysis. Currently, data obtained from multifunctional diagnostic tools is the basis for the developed Russian railway infrastructure maintenance and operation digital model. The strategic development of mobile diagnostic labs is the gradual transition to solutions with advanced digital analysis, supported by artificial intelligence, monitoring and forecasting. The article presents the development of mobile labs for the railroad infrastructure condition diagnosis up to the current solutions, in which measurements take place without human intervention and the obtained information is transmitted in real time to the analysis and decision centres. Keywords: rail transport, measuring wagons, digitisation of railways, Russian railways

An Efficient Shot Boundary Detection Using Data-cube Searching Technique

2020 ◽  
Vol 13 (4) ◽  
pp. 798-807
Author(s):  
J. Kavitha ◽  
P. Arockia Jansi Rani ◽  
P. Mohamed Fathimal ◽  
Asha Paul
Keyword(s):  
Texture Features ◽  
Boundary Detection ◽  
Data Cube ◽  
Multimedia Data ◽  
Shot Boundary Detection ◽  
Gradual Transition ◽  
Detection Rates ◽  
Effective Manner ◽  
Shot Boundary ◽  
Shot Transitions

Background:: In the internet era, there is a prime need to access and manage the huge volume of multimedia data in an effective manner. Shot is a sequence of frames captured by a single camera in an uninterrupted space and time. Shot detection is suitable for various applications such that video browsing, video indexing, content based video retrieval and video summarization. Objective:: To detect the shot transitions in the video within a short duration. It compares the visual features of frames like correlation, histogram and texture features only in the candidate region frames instead of comparing the full frames in the video file. Methods: This paper analyses candidate frames by searching the values of frame features which matches with the abrupt detector followed by the correct cut transition frame with in the datacube recursively until it detects the correct transition frame. If they are matched with the gradual detector, then it will give the gradual transition ranges, otherwise the algorithm will compare the frames within the next datacube to detect shot transition. Results:: The total average detection rates of all transitions computed in the proposed Data-cube Search Based Shot Boundary Detection technique are 92.06 for precision, 96.92 for recall and 93.94 for f1 measure and the maximum accurate detection rate. Conclusion:: Proposed method for shot transitions uses correlation value for searching procedure with less computation time than the existing methods which compares every single frame and uses multi features such as color, edge, motion and texture features in wavelet domain.

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