Global rates and patterns of channel migration in river deltas

2021 ◽  
Vol 118 (46) ◽  
pp. e2103178118
Author(s):  
Teresa Jarriel ◽  
John Swartz ◽  
Paola Passalacqua
Keyword(s):  
Global Scale ◽  
Sediment Flux ◽  
Channel Migration ◽  
Channel Networks ◽  
River Deltas ◽  
Current State ◽  
External Forcings ◽  
Ubiquitous Systems ◽  
Decadal Scale ◽  
The Individual

River deltas are dynamic systems whose channels can widen, narrow, migrate, avulse, and bifurcate to form new channel networks through time. With hundreds of millions of people living on these globally ubiquitous systems, it is critically important to understand and predict how delta channel networks will evolve over time. Although much work has been done to understand drivers of channel migration on the individual channel scale, a global-scale analysis of the current state of delta morphological change has not been attempted. In this study, we present a methodology for the automatic extraction of channel migration vectors from remotely sensed imagery by combining deep learning and principles from particle image velocimetry (PIV). This methodology is implemented on 48 river delta systems to create a global dataset of decadal-scale delta channel migration. By comparing delta channel migration distributions with a variety of known external forcings, we find that global patterns of channel migration can largely be reconciled with the level of fluvial forcing acting on the delta, sediment flux magnitude, and frequency of flood events. An understanding of modern rates and patterns of channel migration in river deltas is critical for successfully predicting future changes to delta systems and for informing decision makers striving for deltaic resilience.

scholarly journals How does the downstream boundary affect avulsion dynamics in a laboratory bifurcation?

2019 ◽  
Vol 7 (4) ◽  
pp. 911-927 ◽  
Author(s):  
Gerard Salter ◽  
Vaughan R. Voller ◽  
Chris Paola
Keyword(s):  
Sediment Flux ◽  
Major Influence ◽  
Channel Networks ◽  
Physical Systems ◽  
River Deltas ◽  
Switching Dynamics ◽  
Frequent Switching ◽  
Two Phases ◽  
Downstream Control

Abstract. Bifurcations play a major role in the evolution of landscapes by controlling how fluxes such as water and sediment are partitioned in distributary and multithread channel networks. In this paper, we present the first experimental investigation on the effect of the downstream boundary on bifurcations. Our experiments in a fixed-wall Y-shaped flume consist of three phases: progradation, transitional, and bypass; the first two phases are net depositional, whereas during the third the sediment flux exiting the downstream boundary matches the input on average. We find that deposition qualitatively changes bifurcation dynamics; we observe frequent switching in the discharge partitioning under net depositional conditions, whereas bypass results in long periods of time where one branch captures most of the flow. We compare our results with a previously developed model for the effect of deposition on bifurcation dynamics. The switching dynamics we observe are more irregular and complex than those predicted by the model. Furthermore, while we observe long periods of time where one branch dominates under bypass conditions, these are not permanent, unlike in the model. We propose that the range of switching timescales we observe arises from a complex interplay of downstream-controlled avulsion and the effect of bars in the upstream channel, including previously unrecognized long-term dynamics associated with a steady bar. Finally, we describe bifurcation experiments conducted with sand but no water. These experiments share the essential feedbacks of our fluvial bifurcation experiments, but do not include bars. In these experiments, we find that the sandpile grows symmetrically while it progrades, but bypass leads to one branch permanently capturing all avalanches. We conclude that the downstream control of deposition vs. bypass is likely a major influence on bifurcation dynamics across a range of physical systems, from river deltas to talus slopes.

scholarly journals How does the downstream boundary affect avulsion dynamics in a laboratory bifurcation?

2019 ◽  
Author(s):  
Gerard Salter ◽  
Vaughan R. Voller ◽  
Chris Paola
Keyword(s):  
Sediment Flux ◽  
Major Influence ◽  
Channel Networks ◽  
Physical Systems ◽  
River Deltas ◽  
Water And Sediment ◽  
Switching Dynamics ◽  
Frequent Switching ◽  
Two Phases ◽  
Downstream Control

Abstract. Bifurcations play a major role in the evolution of landscapes by controlling how fluxes such as water and sediment are partitioned in distributary and multi-thread channel networks. In this paper, we present the first experimental investigation on the effect of the downstream boundary on bifurcations. Our experiments in a fixed-wall Y-shaped flume consist of three phases: progradation, transitional, and bypass; the first two phases are depositional, whereas during the third, the sediment flux exiting the downstream boundary matches the input on average. We find that deposition qualitatively changes bifurcation dynamics; we observe frequent switching in the discharge partitioning under depositional conditions, whereas bypass results in long periods of time where one branch captures most of the flow. We compare our results with a previously developed model for the effect of deposition on bifurcation dynamics. The switching dynamics we observe are more irregular and complex than those predicted by the model. Furthermore, while we observe long periods of time where one branch dominates under bypass conditions, these are not permanent, unlike in the model. We propose that the range of switching timescales we observe arises from a complex interplay of downstream-controlled avulsion, and the effect of bars in the upstream-channel, including previously unrecognized long-timescale bar dynamics. Finally, we describe bifurcation experiments conducted with sand but no water. These experiments share the essential feedbacks of our fluvial bifurcation experiments, but do not include bars. In these experiments, we find that the sandpile grows symmetrically while it progrades, but bypass leads to one branch permanently capturing all avalanches. We conclude that the downstream control of deposition vs. bypass is likely a major influence on bifurcation dynamics across a range of physical systems, from river deltas to talus slopes.

scholarly journals Entropy and optimality in river deltas

2017 ◽  
Vol 114 (44) ◽  
pp. 11651-11656 ◽  
Author(s):  
Alejandro Tejedor ◽  
Anthony Longjas ◽  
Douglas A. Edmonds ◽  
Ilya Zaliapin ◽  
Tryphon T. Georgiou ◽  
...  
Keyword(s):  
Anthropogenic Activities ◽  
Sediment Flux ◽  
Channel Network ◽  
Channel Networks ◽  
Form And Function ◽  
River Deltas ◽  
Self Organized ◽  
Water And Sediment ◽  
Network Topologies ◽  
And Function

The form and function of river deltas is intricately linked to the evolving structure of their channel networks, which controls how effectively deltas are nourished with sediments and nutrients. Understanding the coevolution of deltaic channels and their flux organization is crucial for guiding maintenance strategies of these highly stressed systems from a range of anthropogenic activities. To date, however, a unified theory explaining how deltas self-organize to distribute water and sediment up to the shoreline remains elusive. Here, we provide evidence for an optimality principle underlying the self-organized partition of fluxes in delta channel networks. By introducing a suitable nonlocal entropy rate (nER) and by analyzing field and simulated deltas, we suggest that delta networks achieve configurations that maximize the diversity of water and sediment flux delivery to the shoreline. We thus suggest that prograding deltas attain dynamically accessible optima of flux distributions on their channel network topologies, thus effectively decoupling evolutionary time scales of geomorphology and hydrology. When interpreted in terms of delta resilience, high nER configurations reflect an increased ability to withstand perturbations. However, the distributive mechanism responsible for both diversifying flux delivery to the shoreline and dampening possible perturbations might lead to catastrophic events when those perturbations exceed certain intensity thresholds.

What's the Buzz? The Neuroscience and the Treatment of Tinnitus

2021 ◽  
Author(s):  
Amanda Henton ◽  
Thanos Tzounopoulos
Keyword(s):  
United States ◽  
The United States ◽  
Global Scale ◽  
Current Treatment ◽  
Public Health Issue ◽  
Current State ◽  
Acquired Hearing Loss ◽  
Neurophysiological Mechanisms ◽  
Necessary And Sufficient

Tinnitus is a pervasive public health issue that affects approximately 15% of the United States population. Similar estimates have also been shown on a global scale, with similar prevalence found in Europe, Asia, and Africa. The severity of tinnitus is heterogeneous, ranging from mildly bothersome to extremely disruptive. In the United States, approximately 10-20% of individuals who experience tinnitus report symptoms that severely reduce their quality of life. Due to the huge personal and societal burden, in the last twenty years a concerted effort on basic and clinical research has significantly advanced our understanding and treatment of this disorder. Yet, neither full understanding, nor cure exists. We know that tinnitus is the persistent involuntary phantom percept of internally-generated non-verbal noises and tones, which in most cases is initiated, by acquired hearing loss and maintained only when this loss is coupled with distinct neuronal changes in auditory and extra-auditory brain networks. Yet, the exact mechanisms and patterns of neural activity that are necessary and sufficient for the perceptual generation and maintenance of tinnitus remain incompletely understood. Combinations of animal model and human research will be essential in filling these gaps. Nevertheless, the existing progress in investigating the neurophysiological mechanisms has improved current treatment and highlighted novel targets for drug development and clinical trials. The aim of this review is to thoroughly discuss the current state of human and animal tinnitus research, outline current challenges, and highlight new and exciting research opportunities.

Predicting Psycho-educational Problems in Childhood

1978 ◽  
Vol 3 (3) ◽  
pp. 148-159 ◽  
Author(s):  
Howard S. Adelman
Keyword(s):  
State Of The Art ◽  
Cost Benefit ◽  
Policy Makers ◽  
Health Maintenance ◽  
Ethical Concerns ◽  
Current State ◽  
The Individual ◽  
Assessment Procedures ◽  
Mass Identification ◽  
Ethical Perspectives

Presented are (1) a brief synthesis of several key conceptual and methodological concerns and some ethical perspectives related to identification of psycho-educational problems and (2) conclusions regarding the current state of the art. The conceptual discussion focuses on differentiating prediction from identification and screening from diagnosis; three models used in developing assessment procedures also are presented. Methodologically, the minimal requirements for satisfactory research are described and current problems are highlighted. Three ethical perspectives are discussed; cost-benefit for the individual, models-motives-goals underlying practices, and cost-benefit for the culture. The current state of the art is seen as not supporting the efficacy of the widespread use of currently available procedures for mass screening. Given this point and the methodological and ethical concerns discussed, it is suggested that policy makers reallocate limited resources away from mass identification and toward health maintenance and other approaches to prevention and early-age intervention.

scholarly journals The space "in-between": the relationship order-chaos and the creativity of senior students of Architecture

2020 ◽  
Vol 10 (1) ◽  
pp. 99-122
Author(s):  
Natalya Souza
Keyword(s):  
Rio Grande ◽  
Organizational Environments ◽  
Edge Of Chaos ◽  
Order And Disorder ◽  
Current State ◽  
Adaptive Solutions ◽  
The Individual ◽  
The Relationship ◽  
Senior Students ◽  
Creative Environment

The edge of chaos has been constantly viewed as a metaphor for the current state our world: a constant coexistence of order and disorder. [...] Several authors working within education and organizational environments have highlighted that creators must perform at the ‘edge of chaos’ in order to produce creative and adaptive solutions. [...] This paper aims to discuss the dichotomy between order and disorder in the creative environment (socio- physics aspects) of architecture students from the Universidade Federal do Rio Grande do Norte, Brazil. Particularly, this paper focuses on students who are working on their Final Graduation Work (FGW), because, unlike other tasks, this activity is completed away from the classroom, in a space 'in-between' – in-betweenwork and home spaces, in-between the collective and the individual, in-between order and chaos.

scholarly journals Improving Human Rights Protection on the national and the European Level

2015 ◽  
pp. 36-51
Author(s):  
RUDOLF DUR SCHNUTZ
Keyword(s):  
Human Rights ◽  
National Level ◽  
European Level ◽  
Human Rights Protection ◽  
Current State ◽  
European Court ◽  
Protection Of Human Rights ◽  
Venice Commission ◽  
Effective Remedy ◽  
The Individual

The recent move towards the individual access to constitutional justice is a progress for protection of human rights in Europe. The explicit purpose of these efforts is to settle human rights issues on the national level and to reduce the number of cases at the Strasbourg Court. Such individual complaints have to be designed in a way that makes them an effective remedy which has to be exhausted before a case can be brought before the European Court of Human Rights. This paper points out the current state of these improvements on the national level in a difficult context on the European level and the recommendations of the Venice Commission in this regard.

scholarly journals Keaton og masserne

2009 ◽  
Vol 37 (108) ◽  
pp. 188-217
Author(s):  
Ulrik Schmidt
Keyword(s):  
Body Mass ◽  
Global Scale ◽  
Solid Mass ◽  
Fluid Mass ◽  
Compositional Elements ◽  
The Individual ◽  
The Masses ◽  
Individual Mass ◽  
The Way

Keaton and the Masses:This article explores conflicts between individual and mass and the process of massification (i.e. the becoming and unfolding of masses) as comic potential in Buster Keaton’s physical comedies. This comic potential is basically characterized by a formalized and aestheticized reduction of human individuality when confronted with objective, non-human matter. De-individualization plays an important role in modern comedy in general. With his intense focus on massification, though, Keaton is not only one of the first, but also one of the most dedicated investigators of comic de-individualization by purely physical means.The first part of the article considers the complex relations in Keaton between gag and narrative with specific regard to the conflict between the individual and the masses. Furthermore, the basic compositional elements in Keaton’s cinematographic staging of individual-mass conflicts are explored, including deactivation and isolation of the individual in relation to his immediate surroundings.Subsequently, the different forms of massification in Keaton are examined more closely with reference to variation in their comic potential. Here, Keaton’s masses are grouped into three basic forms: In the solid mass—typically materialized in heavy objects and hard surfaces—the comic potential is due to its ability to violently tumble or jam the pacified individual into de-subjectified body mass. In the fluid mass, the comic potential is basically found in the unmanageable character of the soft, formless and constantly transforming phenomenon. In pure accumulation, Keaton focuses on the comic potential of the very formation of masses as a process of accumulation (i.e., the repetitive addition of discrete, more or less identical elements). Here, Keaton’s interest lies above all in the formation of human masses (crowds).The last section considers Keaton’s cinematographic distribution of individual gags on the global scale of the entire film. Here, it is analyzed how Keaton incessantly glues the individual gags together into one large and seamlessly continuous gag. It is thus concluded that not only is each individual gag characterized by massification, but the way the different gags are interrelated throughout Keaton’s films also has a profound mass character.

scholarly journals Student Feedback on Teaching in Schools: Current State of Research and Future Perspectives

2021 ◽  
pp. 259-271
Author(s):  
Wolfram Rollett ◽  
Hannah Bijlsma ◽  
Sebastian Röhl
Keyword(s):  
Student Perceptions ◽  
Teaching Quality ◽  
Student Feedback ◽  
Comprehensive Overview ◽  
Feedback Information ◽  
Current State ◽  
Feedback Culture ◽  
State Of Research ◽  
The Individual ◽  
High Level

AbstractThe aim of this volume was to give a comprehensive overview of the current state of the research on student perceptions of and student feedback on teaching. This chapter provides a resume of the important theoretical considerations and empirical evidence the authors contributed to this volume. First, evidence concerning the validity of student perceptions of teaching quality is discussed, highlighting the quality of the questionnaires used and accompanying materials provided by their authors. In the next step, empirical findings are summarized on student and teacher characteristics that can influence important processes within the feedback cycle. Subsequently, it is emphasized that the effectiveness of student feedback on teaching is significantly related to the nature of the individual school’s feedback culture. Furthermore, it is argued that the efficacy of student feedback depends on whether teachers are provided with a high level of support, when making use of the feedback information to improve their teaching practices. As the literature review impressively documents‚ teachers, teaching, and ultimately students can benefit substantially from student feedback on teaching in schools.

scholarly journals The role of the emotions of guilt and shame in methodology of research on social emotions

2021 ◽  
pp. 11-25
Author(s):  
Alexandra Shiller
Keyword(s):  
Cultural Psychology ◽  
Cross Cultural ◽  
Social Emotions ◽  
History Of Research ◽  
Current State ◽  
History Of ◽  
Methodological Problems ◽  
The Individual ◽  
Methodology Of Science

This article is dedicated to examination of the role of guilt and shame, namely to prevalence one of these emotions in a particular culture as the leading mechanism of social control. The prevalence of guilt or shame as a cultural “dimension” has become one of the first criteria for the division of cultures into Western and Eastern, and was used by the researchers as a basic postulate for cross-cultural r. Over time, the perception of emotions as the criterion for the division of cultures has been revised. The article traces the history of research on emotions in general, namely the emotions of guilt and shame as social emotions, as well as describes guilt and shame as collective and individual experiences. Analysis is conducted on the role of guilt and shame in methodology of research on social emotions, cross-cultural studies. The author outlines certain methodological problems and contradictions, and assesses the current state of scientific research dedicated to social emotions. The conclusion is made that the research on collective sense of guilt and shame is more advanced from the perspective of cross-cultural psychology and philosophy, as well as the overall methodology of science; it allows shifting from the study of the role of individual emotions in interpersonal (conditioned by collective ties), intergroup and intragroup communication towards the integrated study of emotions associated with interaction of the individual and society, i.e. social experiences.

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