Considerations When Applying Large-Scale PIV and PTV for Determining River Flow Velocity

Large-scale image velocimetry is a novel approach for non-contact remote sensing of flow in rivers. Research within this topic has largely focussed on developing specific aspects of the image velocimetry work-flow, or alternatively, testing specific tools or software using case studies. This has resulted in the development of a multitude of techniques, with varying practice being employed between groups, and authorities. As such, for those new to image velocimetry, it may be hard to decipher which methods are suited for particular challenges. This research collates, synthesises, and presents current understanding related to the application of particle image velocimetry (PIV) and particle tracking velocimetry (PTV) approaches in a fluvial setting. The image velocimetry work-flow is compartmentalised into sub-systems of: capture optimisation, pre-processing, processing, and post-processing. The focus of each section is to provide examples from the wider literature for best practice, or where this is not possible, to provide an overview of the theoretical basis and provide examples to use as precedence and inform decision making. We present literature from a range of sources from across the hydrology and remote sensing literature to suggest circumstances in which specific approaches are best applied. For most sub-systems, there is clear research or precedence indicating how to best perform analysis. However, there are some stages in the process that are not conclusive with one set method and require user intuition or further research. For example, the role of external environmental conditions on the performance of image velocimetry being a key aspect that is currently lacking research. Further understanding in areas that are lacking, such as environmental challenges, is vital if image velocimetry is to be used as a method for the extraction of river flow information across the range of hydro-geomorphic conditions.

Download Full-text

The scientific issues surrounding remote detection of submerged coral ecosystems

Progress in Physical Geography Earth and Environment ◽

10.1177/030913339802200203 ◽

1998 ◽

Vol 22 (2) ◽

pp. 190-221 ◽

Cited By ~ 21

Author(s):

Heather Holden ◽

Ellsworth LeDrew

Keyword(s):

Remote Sensing ◽

Coral Reef ◽

Coral Reefs ◽

Large Scale ◽

Aerial Photographs ◽

Coastal Zones ◽

Global Status ◽

Coral Reef Ecosystems ◽

Remote Estimation

According to the 1993 colloquium on the ‘Global status of coral reefs', our understanding of the global role of coral reefs is inadequate. To increase our understanding, an accurate large-scale mapping and monitoring programme is necessary. Historically, coastal zones have been mapped using traditional surveying tools such as topographic maps, nautical charts, existing aerial photographs and direct observations. Although less expensive than digital imagery, exclusive use of these traditional tools may not be practical for monitoring large or remote coral reef ecosystems accurately. Researchers are attempting to develop an adequate coral reef mapping system based on digital remote sensing, but are impeded by issues such as effects of the intervening water column and spectral distinction of bottom types. The two variables discussed, which will contribute to our understanding of the global role of coral reefs, are: 1) remote sensing of submerged coral reefs in general; and 2) remote sensing of coral bleaching in particular. A summary of radiative transfer theory is presented and case studies of attempts at mapping remotely the geographic extent and health of submerged ecosystems, as well as a discussion of the remote estimation of water depth and quality. Problems in the translation and delivery of information to the end user are presented, and possible solutions suggested.

Download Full-text

The role of multi-sensor remote sensing for drought characterization: challenges and opportunities

10.5194/egusphere-egu21-1849 ◽

2021 ◽

Author(s):

Lixin Wang ◽

Wenzhe Jiao ◽

Matthew McCabe

Keyword(s):

Remote Sensing ◽

Large Scale ◽

Tree Mortality ◽

Drought Monitoring ◽

Drought Indices ◽

Spatiotemporal Resolution ◽

Continental Scale ◽

Related Information ◽

Challenges And Opportunities

<p>Satellite based remote sensing plays important role in studying regional to continental scale drought. One of the unique elements of remote sensing platforms is their multi-sensor capabilities, which enhance the capacity for characterizing drought from a variety of aspects. However, multi-sensor integrated drought evaluation is in its infancy. To advocate and encourage on-going exploration and integration of multi-sensor remote sensing for drought studies, we provide an overview of the role of multi-sensor remote sensing for addressing knowledge gaps and driving advances in drought studies. We first present a comprehensive summary of large-scale drought-related remote sensing datasets that can be used for multi-sensor drought studies. Then we provide a detailed review of how the integrated multi-sensor remote sensing could enhance our analysis in multiple important drought related phenomena and mechanisms such as drought-induced tree mortality, drought-related ecosystem fires, post-drought recovery and legacy effects, flash drought, and drought trends under climate change. We also provide a summary of recent modeling advances towards developing integrated multi-sensor remote sensing drought indices. We highlight that leveraging multi-sensor remote sensing provides unique benefits for regional to global drought studies, particularly in: 1) revealing the complex drought impact mechanisms on various ecosystem components; 2) providing continuous long-term drought related information at large scales; 3) presenting real-time drought information with high spatiotemporal resolution; 4) providing multiple lines of evidence of drought monitoring to improve modeling and prediction robustness; and 5) improving the accuracy of drought monitoring and assessment efforts.</p>

Download Full-text

Adolescents who Engage in Nonsuicidal Self-Injury (NSSI)

Emotion Regulation and Psychopathology in Children and Adolescents ◽

10.1093/med:psych/9780198765844.003.0019 ◽

2017 ◽

pp. 398-416

Author(s):

David Voon ◽

Penelope Hasking

Keyword(s):

Emotion Regulation ◽

Large Scale ◽

Best Practice ◽

Emotional Reactivity ◽

The Body ◽

Emotional States ◽

Self Injury ◽

Self Harm ◽

Nonsuicidal Self Injury

Nonsuicidal self-injury (NSSI) refers to intentional damage to the body without fatal intent. While distal factors such as genetic predisposition, emotional sensitivity, emotional reactivity and invalidating childhood environments may serve as risk factors, NSSI is primarily maintained by alleviation of intense negative emotional states, in the absence of alternative emotion regulation strategies. Currently, no specific NSSI intervention for adolescents exists; however, extant self-harm interventions have demonstrated promising, preliminary findings. Of note, the salient role of emotion regulation in the initiation and maintenance of NSSI suggests this may be a viable treatment target. While empirical evidence supports this in adult samples, replication in large-scale, randomized controlled trials with adolescent samples is required to inform best practice in treating NSSI among adolescents.

Download Full-text

The use of exercises to enhance and assess interlocal collaboration in preparedness: A qualitative analysis

Journal of Emergency Management ◽

10.5055/jem.2015.0259 ◽

2016 ◽

Vol 13 (6) ◽

pp. 499

Author(s):

Nicole A. Errett, PhD, MSPH, CPH, CE ◽

Shannon Frattaroli, PhD, MPH ◽

Daniel J. Barnett, MD, MPH ◽

Beth A. Resnick, MPH ◽

Lainie Rutkow, PhD, JD, MPH

Keyword(s):

Emergency Preparedness ◽

Policy Development ◽

Large Scale ◽

Best Practice ◽

Future Research ◽

Emergency Plan ◽

Semistructured Interviews ◽

Development Support ◽

Assessment Strategies

Introduction: Interlocal collaboration, or collaboration among neighboring independent municipalities, has been generally accepted as an emergency preparedness strategy. In the absence of large-scale disasters, emergency preparedness exercises may serve to test the effectiveness of interlocal collaboration on emergency preparedness. However, the use of emergency preparedness exercises to enhance or assess interlocal collaboration, or its impact on preparedness, requires additional empirical exploration. Hypothesis/problem: This exploratory study aims to understand the perspectives of key informants (KIs) with broad knowledge of the history, goals, and implementation of the Urban Area Security Initiative (UASI) program, as well as knowledge of interlocal collaboration exercises conducted as part of the UASI program, about the role of exercises in improving and assessing interlocal collaboration for emergency preparedness.Method: In early 2014, 28 KIs were interviewed during 24 semistructured interviews. Interviews were recorded and analyzed to identify key themes related to emergency preparedness exercises and the enhancement and assessment of interlocal collaboration.Results: KIs perceived exercises to enhance interlocal collaboration in preparedness by promoting regional, interlocal: risk assessment; emergency plan testing and operationalization; relationship development; support for regional plans and operational structures; capability delivery practice; best practice sharing across interlocal collaborations; and engagement of elected or senior leadership in interlocal preparedness endeavors. Exercise participants, scenarios, administration, formats, and assessment strategies to promote interlocal collaboration were identified. Conclusions: Seven distinct mechanisms by which exercises can enhance interlocal collaboration that can be used to guide future research and policy development were identified. The format, scenario, participation, and administration of emergency preparedness exercises can be tailored to enhance collaboration.

Download Full-text

Material worlds

The Oxford Handbook of the European Iron Age ◽

10.1093/oxfordhb/9780199696826.013.25 ◽

2018 ◽

Author(s):

Fraser Hunter

Keyword(s):

Material Culture ◽

Iron Age ◽

Experimental Work ◽

Large Scale ◽

Best Practice ◽

New Technologies ◽

Single Region ◽

Mediterranean World ◽

The Everyday

This chapter considers material culture themes beyond any single region or country in order to look at recurring problems and possibilities across the European Iron Age. Often these are analogies (such as problems of taphonomic bias) rather than direct linkages, but large-scale issues in European prehistory are also considered, such as the development, selective adoption, and adaptation of new technologies, linkages to the Mediterranean world, and the role of art. Major areas of untapped research in the archaeology of the everyday are highlighted: the tools and other items which are often ignored beyond specialist reports can provide great insights into the changing lives of people in Iron Age Europe. Here, best practice in other areas and periods, along with experimental work, could cast fresh light on these fascinating material worlds.

Download Full-text

MEASUREMENT OF INUNDATING FLOW FROM A BROKEN ENBANKMENT BY USING VIDEO IMAGES SHOOT FROM A MEDIA HELICOPTER

E3S Web of Conferences ◽

10.1051/e3sconf/20184006001 ◽

2018 ◽

Vol 40 ◽

pp. 06001

Author(s):

Ichiro Fujita ◽

Yuichi Notoya ◽

Takanori Furuta

Keyword(s):

Large Scale ◽

Particle Image ◽

Heavy Rain ◽

Surface Velocity ◽

Water Volume ◽

Video Images ◽

Image Velocimetry ◽

Flow Information ◽

Scale Particle ◽

Time Image

The heavy rain disaster in the Kinugawa River basin that occurred along with the passage of the Typhoon 18 caused the embankment destruction in the middle reach of the river on September 10, 2015. Due to the overflow, the houses in the vicinity of the embankment collapsed, causing a flood inundation spreading over a wide area. Because the embankment breakwater occurred during the daytime, the state of the inundating flow was recorded from various angles by media helicopters or drones. In this study, we developed a method to extract quantitative flow information from a helicopter video image in which the shooting position and angles are changed one after another, because it was taken in emergency. In the analysis, the images were orthorectified after stabilizing the images, from which surface velocity distributions were measured by image-based technique such as the large-scale particle image velocimetry (LSPIV) or the space-time image velocimetry (STIV). As a result, the time change of water entering from the broken embankment and the total inundated water volume during the disaster were estimated. In addition, two-dimensional surface velocity distributions were analysed to show the spreading of inundated flow.

Download Full-text

Metrics for the Quantification of Seeding Characteristics to Enhance Image Velocimetry Performance in Rivers

Remote Sensing ◽

10.3390/rs12111789 ◽

2020 ◽

Vol 12 (11) ◽

pp. 1789 ◽

Cited By ~ 2

Author(s):

Silvano Fortunato Dal Sasso ◽

Alonso Pizarro ◽

Salvatore Manfreda

Keyword(s):

Water Resource Management ◽

Large Scale ◽

River Flow ◽

Low Cost ◽

A Priori ◽

Surface Flow ◽

Seeding Density ◽

Unmanned Aerial Systems ◽

Flow Monitoring ◽

Image Velocimetry

River flow monitoring is essential for many hydraulic and hydrologic applications related to water resource management and flood forecasting. Currently, unmanned aerial systems (UASs) combined with image velocimetry techniques provide a significant low-cost alternative for hydraulic monitoring, allowing the estimation of river stream flows and surface flow velocities based on video acquisitions. The accuracy of these methods tends to be sensitive to several factors, such as the presence of floating materials (transiting onto the stream surface), challenging environmental conditions, and the choice of a proper experimental setting. In most real-world cases, the seeding density is not constant during the acquisition period, so it is not unusual for the patterns generated by tracers to have non-uniform distribution. As a consequence, these patterns are not easily identifiable and are thus not trackable, especially during floods. We aimed to quantify the accuracy of particle tracking velocimetry (PTV) and large-scale particle image velocimetry (LSPIV) techniques under different hydrological and seeding conditions using footage acquired by UASs. With this aim, three metrics were adopted to explore the relationship between seeding density, tracer characteristics, and their spatial distribution in image velocimetry accuracy. The results demonstrate that prior knowledge of seeding characteristics in the field can help with the use of these techniques, providing a priori evaluation of the quality of the frame sequence for post-processing.

Download Full-text

Variability of low flow magnitudes in the Upper Colorado River Basin: identifying trends and relative role of large-scale climate dynamics

Hydrology and Earth System Sciences Discussions ◽

10.5194/hessd-11-8779-2014 ◽

2014 ◽

Vol 11 (7) ◽

pp. 8779-8802 ◽

Cited By ~ 4

Author(s):

M. Pournasiri Poshtiri ◽

I. Pal

Keyword(s):

River Basin ◽

Large Scale ◽

River Flow ◽

Colorado River ◽

Colorado River Basin ◽

Low Flow ◽

Anthropogenic Factors ◽

Relative Role ◽

Water Abstraction

Abstract. Low flow magnitude in a head water basin is important for planners because minimum available amount of water in a given time period often leads to concerns regarding serious repercussions, in both up and downstream regions. This is a common scenario in arid region like Colorado River basin located in the southwestern US. Low flow variability in Colorado River is due to complex interactions between several natural and anthropogenic factors; but we aim to identify the relative role of climate on varying low flow magnitudes at different spatial locations. The research questions we aim to answer are: Is there a systematic variability in water availability during the driest time of a year or season? How does that vary across locations and is there a link between large-scale climate and low flow variations? Towards that aim we select 17 stream gauge locations, which are identified as "undisturbed" meaning that these stations represent near-natural river flow regimes in the headwater region of Colorado River, which provides a useful resource for assessment of climate and hydrology associations without the confounding factor of major direct (e.g. water abstraction) or indirect (e.g. land-use change) human modification of flows. A detailed diagnostic analysis gives us fair understanding on the variability of low flow magnitude that is explained by climate. We also present spatial heterogeneity of hydro-climatological linkages that is important for suitable adaptive management measures.

Download Full-text