scholarly journals Assessment and ranking flood events in a regulated river using information and complexity measures

2021 ◽  
Vol 2090 (1) ◽  
pp. 012169
Author(s):  
Mohamad Basel Al Sawaf ◽  
Kiyosi Kawanisi ◽  
Cong Xiao
Keyword(s):  
Risk Control ◽  
River System ◽  
River Regulation ◽  
Environmental Risks ◽  
Regulated River ◽  
Flood Events ◽  
Regulated Rivers ◽  
Complexity Measures ◽  
Complexity Metrics

Abstract The availability of a robust approach that describe the hidden features of flood events in regulated rivers is of great importance. The key goal of this research is to utilize some of information and complexity measures to assess and rank flood patterns within a regulated river system. To meet this goal, the Metric Entropy (ME) as measure of information content and Rényi Complexity (CR) as a quantification for complexity content were employed. To examine the role of river regulation on flood risk control, river stage records of two monitoring stations located at downstream of two different dams were considered in this research. The findings show that information and complexity metrics offer an image of the randomness embedded in dataset and the presence of internal patterns in studied data records. In general, this research shows that natural environmental risks and disasters can be assessed and ranked using a promising physical scheme based on information and complexity measures.

scholarly journals Isolating causal pathways between flow and fish in the regulated river hierarchy

2015 ◽  
Vol 72 (11) ◽  
pp. 1731-1748 ◽  
Author(s):  
Ryan A. McManamay ◽  
Brandon K. Peoples ◽  
Donald J. Orth ◽  
Charles A. Dolloff ◽  
David C. Matthews
Keyword(s):  
Structural Equation ◽  
Large Scale ◽  
Fish Assemblages ◽  
Causal Structure ◽  
River Regulation ◽  
Regulated River ◽  
Equation Modeling ◽  
Regulated Rivers ◽  
Causal Pathways ◽  
The Hierarchical Structure

Unregulated river systems are organized in a hierarchy in which large-scale factors (i.e., landscape and segment scales) influence local habitats (i.e., reach, meso-, and microhabitat scales), and both differentially exert selective pressures on biota. Dams, however, create discontinua in these processes and change the hierarchical structure. We examined the relative roles of hydrology and other instream factors, within a hierarchical landscape context, in organizing fish communities in regulated and unregulated tributaries to the Upper Tennessee River, USA. We used multivariate regression trees to identify factors that partition fish assemblages based on trait similarities, irrespective of spatial scale. We then used classical path analysis and structural equation modeling to evaluate the most plausible hierarchical causal structure of specific trait-based community components, given the data. Both statistical approaches suggested that river regulation affects stream fishes through a variety of reach-scale variables, not always through hydrology itself. Although we observed different changes in flow, temperature, and biotic responses according to regulation types, the most predominant path in which dam regulation affected biota was via temperature alterations. Diversion dams had the strongest effects on fish assemblages. Diversion dams reduced flow magnitudes, leading to declines in fish richness but increased temperatures, leading to lower abundances in equilibrium species and nest guarders. Peaking and run-of-river dams increased flow variability, leading to lower abundances in nest-guarding fishes. Flow displayed direct relationships with biotic responses; however, results indicated that changes in temperature and substrate had equal, if not stronger, effects on fish assemblage composition. The strength and nature of relationships depended on whether flow metrics were standardized for river size. We suggest that restoration efforts in regulated rivers focus on improving flow conditions in conjunction with temperature and substrate restoration.

Migration patterns and estuarine aggregations of a catadromous fish, Australian bass (Percalates novemaculeata) in a regulated river system

2017 ◽  
Vol 68 (8) ◽  
pp. 1544 ◽  
Author(s):  
D. J. Harding ◽  
R. G. Dwyer ◽  
T. M. Mullins ◽  
M. J. Kennard ◽  
R. D. Pillans ◽  
...  
Keyword(s):  
Fish Species ◽  
Large Scale ◽  
River System ◽  
Regulated River ◽  
Regulated Rivers ◽  
Migration Patterns ◽  
Migratory Response ◽  
Resource Managers ◽  
Receiver Array ◽  
Downstream Movement

Catadromous fish species require adequate flows to migrate between fresh and saltwater habitats to reproduce. However, artificial barriers and flow alteration affect fish populations by reducing habitat connectivity and disrupting movement cues. In regulated rivers, it is critical that migratory flow requirements are quantified to optimise water allocation for multiple users. In the present study, we assessed the migratory timing, flow and estuarine aggregation requirements for Australian bass (Percalates novemaculeata). Over 2 years, 66 bass were tracked using an acoustic receiver array in the Logan River (Qld, Australia). Bass performed large-scale downstream movements in response to elevated winter flows (40 and 108m3 s–1), which facilitated migration to the lower estuary, where salinity conditions were appropriate for spawning. Bass migrations occurred only when gonads were mature, despite large flows providing opportunities for movement outside this period. Experimental flow releases from an impoundment (2.1m3 s–1) during winter did not elicit a migratory response. Connectivity between upstream and estuarine habitats was reduced by the presence of instream weirs, with downstream movement across weirs occurring only when sufficient flow magnitude was achieved (>76.1m3 s–1). These findings are relevant for water resource managers formulating environmental flow rules for catadromous fish species in systems with multiple instream artificial barriers.

Environmental flow management using transparency and translucency rules

2014 ◽  
Vol 65 (8) ◽  
pp. 667 ◽  
Author(s):  
Ivor Growns ◽  
Ivars Reinfelds
Keyword(s):  
Flow Regime ◽  
River Flow ◽  
River System ◽  
Flow Regimes ◽  
Management Technique ◽  
Flood Events ◽  
Regulated Rivers ◽  
Flow Alteration ◽  
Natural Flow ◽  
Historical Flow

River flow regimes and their variability are considered by many authors to be the most important factor structuring their physical and ecological environment. In regulated rivers, environmental or instream flows are the main management technique used to ameliorate the ecological effects of flow alteration. We highlight two concepts that are not commonly used in a managed flow regime but help return natural flow variability to a managed river, namely, transparent and translucent flow rules. Transparency flows target lower flows up to a defined threshold so that all inflows are released from a dam or are protected from abstraction. Translucency flows form a percentage of inflows greater than the transparency threshold that are released to maintain a proportion of flow pulses in the river system. The main ecological concept underlying transparency and translucency flows is that riverine biota are adapted to the historical flow regime. Although the loss of small to moderate flood events may arise from implementation of translucency and/or transparency flow regimes, we advocate that these rule types would, nonetheless, be beneficial in many managed flow regimes and present two case studies where they have been defined and implemented.

Can tributary in-flows improve the recovery of the dissolved organic carbon regime in a snowmelt river regulated by a large reservoir?

2016 ◽  
Vol 67 (9) ◽  
pp. 1338 ◽  
Author(s):  
Ann-Marie Rohlfs ◽  
Simon M. Mitrovic ◽  
Simon Williams ◽  
Daniel Coleman
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
River System ◽  
Main Stem ◽  
Water Diversion ◽  
Regulated River ◽  
Regulated Rivers ◽  
Large Reservoir ◽  
Doc Export ◽  
Doc Concentration

Although tributary inputs can accelerate the recovery of many physical and chemical gradients below large reservoirs, their contribution to the dissolved organic carbon (DOC) regime in regulated rivers remains poorly studied. In some regulated tributaries, flow volumes can be manipulated, potentially influencing DOC supply to the main stem. The present study examines how tributary water diversion affects DOC supply to a snowmelt river regulated by large reservoirs. DOC concentration was measured at tributary and main stem sites, and tributary DOC export was estimated under different tributary flow-diversion scenarios. Significant, positive correlations between DOC concentration and discharge were absent directly below the dam, but were present in the unregulated tributary, and re-emerged below the tributary confluence. Irrespective of water-diversion practices, tributary in-flows reconnected the regulated main stem to a more variable DOC regime driven by catchment flushing processes. However, tributary water diversion dampened the tributary signal by reducing DOC pulse frequency and total DOC export to the regulated river. These aspects of the DOC regime may influence basal resource availability and ecosystem functioning in the regulated main stem. The present study illustrates how an ecologically valuable tributary function can be addressed and quantified to guide the management and rehabilitation of a regulated river system.

scholarly journals Saving Up for a Rainy Day? Savings Groups and Resilience to Flooding in Dar es Salaam, Tanzania

Urban Forum ◽  
2021 ◽  
Author(s):  
Alexandra Panman ◽  
Ian Madison ◽  
Nyambiri Nanai Kimacha ◽  
Jean-Benoît Falisse
Keyword(s):  
Urban Areas ◽  
Banking Sector ◽  
Urban Climate ◽  
Dar Es Salaam ◽  
Group Model ◽  
Flood Events ◽  
Community Initiatives ◽  
Qualitative Evidence ◽  
Flexible Form

AbstractThis paper explores the role of savings groups in resilience to urban climate-related disasters. Savings groups are a rapidly growing phenomenon in Africa. They are decentralized, non-institutional groups that provide millions of people excluded from the formal banking sector with a trusted, accessible, and relatively simple source of microfinance. Yet there is little work on the impacts of savings groups on resilience to disasters. In this paper, we use a combination of quantitative and qualitative evidence from Dar es Salaam (Tanzania) to shed new light on the role that savings groups play in helping households cope with climate-related shocks. Drawing on new data, we show that approximately one-quarter of households have at least one member in a group, and that these households recover from flood events faster than those who do not. We further argue that the structure of savings groups allows for considerable group oversight, reducing the high costs of monitoring and sanctioning that often undermine cooperative engagement in urban areas. This makes the savings group model a uniquely flexible form of financing that is well adapted to helping households cope with shocks such as repeated flooding. In addition to this, we posit that they may provide a foundation for community initiatives focusing on preventative action.

Performance evaluation of alternate policies on reservoir system operation

1986 ◽  
Vol 13 (2) ◽  
pp. 203-212 ◽  
Author(s):  
J. R. Weeraratne ◽  
Lloyd Logan ◽  
T. E. Unny
Keyword(s):  
River System ◽  
Primary Objective ◽  
Performance Criteria ◽  
Decision Making Process ◽  
System Failure ◽  
System Operation ◽  
System Vulnerability ◽  
Operational Policies ◽  
System Robustness

This paper discusses within the context of the Grand River system operation the application of the three performance criteria introduced earlier by T. Hashimoto, D. P. Loucks, and J. R. Stedinger. These criteria evaluate the performance characteristic in respect to system failure, system recovery, and system vulnerability with regard to extreme (costly) failures for alternative operational policies. System robustness, also discussed by Hashimoto and co-workers, is used to measure the economic flexibility of system operation to adapt to uncertainties of future demand. The primary objective of the presentation made herein is to establish the role of these criteria in a decision-making process in the operation of the system.

The role of task sequencing in fluency, accuracy, and complexity: Investigating the SSARC model of pedagogic task sequencing

2018 ◽  
Vol 24 (5) ◽  
pp. 642-665 ◽  
Author(s):  
Aleksandra Malicka
Keyword(s):  
Cognitive Complexity ◽  
Speech Rate ◽  
Structural Complexity ◽  
Simple Complex ◽  
Complexity Measures ◽  
Complex Sequence ◽  
Task Sequencing ◽  
Sequence Versus ◽  
Individual Task

This study set out to test the theoretical premise of the SSARC model of pedagogic task sequencing, which postulates that tasks should be sequenced for learners from cognitively simple to complex. This experiment compared the performance of three tasks differing in cognitive complexity in a simple–complex sequence versus in the absence of any other tasks. There were two groups in the study: (1) participants who performed the three tasks in the simple–complex sequence, and (2) participants who performed either the simple, the complex, or the most complex task. The participants’ speech was analysed using fluency, accuracy, and complexity measures. The results indicate that simple–complex sequencing led to a higher speech rate, greater dysfluency, enhanced accuracy, and greater structural complexity, as compared to individual task performance. The results are discussed in terms of the SSARC model and pedagogical implications of the findings are presented.

scholarly journals Megacities in climate governance: the case of Rio de Janeiro

2016 ◽  
Vol 17 ◽  
Author(s):  
Alberto Teixeira Da Silva ◽  
Mercedes Pardo Buendía
Keyword(s):  
Technological Innovation ◽  
Rio De Janeiro ◽  
Vital Role ◽  
Environmental Risks ◽  
Climate Governance ◽  
Latent Form ◽  
Domestic Policies ◽  
Social Empowerment

This paper shows the vital role of cities in climate governance, as places where the crisis is expressed in latent form, but also as emblematic spaces in terms of technological innovation and social empowerment. It discusses challenges of megacities like Rio de Janeiro, given their vulnerability, resilience and environmental risks to the transition of a more intelligent and sustainable patterns of urbanization, through its domestic policies and paradiplomacy networks.Este artigo mostra o papel vital das cidades na governança do clima, como lugares onde a crise se expressa de forma latente, mas também como espaços emblemáticos em termos de inovação tecnológica e empoderamento social. Discute os desafios de megacidades como Rio de Janeiro, considerando suas vulnerabilidades, riscos socioambientais e resiliências para a transição de modelos mais inteligentes e sustentáveis de urbanização, através de suas políticas domésticas e redes de paradiplomacia. 

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