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  1. Article: Climate‐Change Controls on River Delta Avulsion Location and Frequency

    Chadwick, A. J. / Lamb, M. P.

    Journal of geophysical research. 2021 June, v. 126, no. 6

    2021  

    Abstract: Coastal rivers that build deltas undergo repeated avulsion events—that is, abrupt changes in river course—which we need to understand to predict land building and flood hazards in coastal landscapes. Climate change can impact water discharge, flood ... ...

    Abstract Coastal rivers that build deltas undergo repeated avulsion events—that is, abrupt changes in river course—which we need to understand to predict land building and flood hazards in coastal landscapes. Climate change can impact water discharge, flood frequency, sediment supply, and sea level, all of which could impact avulsion location and frequency. Here we present results from quasi‐2D morphodynamic simulations of repeated delta‐lobe construction and avulsion to explore how avulsion location and frequency are affected by changes in relative sea level, sediment supply, and flood regime. Model results indicate that relative sea‐level rise drives more frequent avulsions that occur at a distance from the shoreline set by backwater hydrodynamics. Reducing the sediment supply relative to transport capacity has little impact on deltaic avulsions, because, despite incision in the upstream trunk channel, deltas can still aggrade as a result of progradation. However, increasing the sediment supply relative to transport capacity can shift avulsions upstream of the backwater zone because aggradation in the trunk channel outpaces progradation‐induced delta aggradation. Increasing frequency of overbank floods causes less frequent avulsions because floods scour the riverbed within the backwater zone, slowing net aggradation rates. Results provide a framework to assess upstream and downstream controls on avulsion patterns over glacial‐interglacial cycles, and the impact of land use and anthropogenic climate change on deltas.
    Keywords climate change ; geophysics ; hydrodynamics ; land use ; research ; river deltas ; rivers ; sea level ; sediments ; shorelines ; stream channels
    Language English
    Dates of publication 2021-06
    Publishing place John Wiley & Sons, Ltd
    Document type Article
    Note JOURNAL ARTICLE
    ISSN 2169-9003
    DOI 10.1029/2020JF005950
    Database NAL-Catalogue (AGRICOLA)

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  2. Article: Channel Migration in Experimental River Networks Mapped by Particle Image Velocimetry

    Chadwick, A. J. / Steel, E. / Williams‐Schaetzel, R. A. / Passalacqua, P. / Paola, C.

    Journal of geophysical research. 2022 Jan., v. 127, no. 1

    2022  

    Abstract: Deltaic river networks naturally reorganize as interconnected channels move to redistribute water, sediment, and nutrients across the delta plain. Network change is documented in decades of satellite imagery and laboratory experiments, but our ability to ...

    Abstract Deltaic river networks naturally reorganize as interconnected channels move to redistribute water, sediment, and nutrients across the delta plain. Network change is documented in decades of satellite imagery and laboratory experiments, but our ability to measure and understand channel movements is limited: existing methods are difficult to employ efficiently and struggle to distinguish between gradual movements (channel migration) and abrupt shifts in river course (channel avulsions). Here, we present a method to extract channel migration from plan‐view imagery using particle image velocimetry (PIV). Although originally designed to track particles moving in a fluid, PIV can be adapted to track channels moving on the delta surface, based on input estimates of channel width, migration timescale, and maps of the wet‐dry interface. Results for a delta experiment show that PIV‐derived vector fields accurately capture channel‐bank movements, as compared to manually drawn maps and an independent image‐registration technique. Unlike other methods, PIV targets the process of channel migration, excluding changes associated with channel avulsions and overbank flow. PIV‐derived migration rates from the experiment span an order of magnitude and are reduced under lower sediment supply and during sea‐level rise, supporting recent models. Together, results indicate that PIV offers a fast and reliable way to measure channel migration in river networks, that channel migration rates under non‐cohesive conditions can displace channels a distance comparable to their width in the time needed to aggrade ∼10% of the channel depth, and that migration direction is ∼60% orthogonal to mean flow direction and ∼40% flow‐parallel overall.
    Keywords geophysics ; particle image velocimetry ; remote sensing ; research ; rivers ; sea level ; sediments
    Language English
    Dates of publication 2022-01
    Publishing place John Wiley & Sons, Ltd
    Document type Article
    Note JOURNAL ARTICLE
    ISSN 2169-9003
    DOI 10.1029/2021JF006300
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  3. Article: Effect of Sea‐Level Change on River Avulsions and Stratigraphy for an Experimental Lowland Delta

    Chadwick, A. J. / Steele, S. / Silvestre, J. / Lamb, M. P.

    Journal of geophysical research. 2022 July, v. 127, no. 7

    2022  

    Abstract: Lowland deltas experience natural diversions in river course known as avulsions. River avulsions pose catastrophic flood hazards and redistribute sediment that is vital for sustaining land in the face of sea‐level rise. Avulsions also affect deltaic ... ...

    Abstract Lowland deltas experience natural diversions in river course known as avulsions. River avulsions pose catastrophic flood hazards and redistribute sediment that is vital for sustaining land in the face of sea‐level rise. Avulsions also affect deltaic stratigraphic architecture and the preservation of sea‐level cycles in the sedimentary record. Here, we present results from an experimental lowland delta with persistent backwater effects and systematic changes in the rates of sea‐level rise and fall. River avulsions repeatedly occurred where and when the river aggraded to a height of nearly half the channel depth, giving rise to a preferential avulsion node within the backwater zone regardless of sea‐level change. As sea‐level rise accelerated, the river responded by avulsing more frequently until reaching a maximum frequency limited by the upstream sediment supply. Experimental results support recent models, field observations, and experiments, and suggest anthropogenic sea‐level rise will introduce more frequent avulsion hazards farther inland than observed in recent history. The experiment also demonstrated that avulsions can occur during sea‐level fall—even within the confines of an incised valley—provided the offshore basin is shallow enough to allow the shoreline to prograde and the river to aggrade. Avulsions create erosional surfaces within stratigraphy that bound beds reflecting the amount of deposition between avulsions. Avulsion‐induced scours overprint erosional surfaces from sea‐level fall, except when the cumulative drop in sea‐level is greater than the channel depth and less than the basin depth. Results imply sea‐level signals outside this range are removed or distorted in delta deposits.
    Keywords basins ; geophysics ; research ; rivers ; sea level ; sediments ; shorelines ; stratigraphy
    Language English
    Dates of publication 2022-07
    Publishing place John Wiley & Sons, Ltd
    Document type Article
    Note JOURNAL ARTICLE
    ISSN 2169-9003
    DOI 10.1029/2021JF006422
    Database NAL-Catalogue (AGRICOLA)

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  4. Article: Differential Bank Migration Limits the Lifespan and Width of Braided Channel Threads

    Chadwick, A. J. / Steel, E. / Passalacqua, P. / Paola, C.

    Water resources research. 2022 Aug., v. 58, no. 8

    2022  

    Abstract: Successful management of flooding and erosion hazards on floodplains depends on our ability to predict a river channel's shape and the lifespan during which it will continue to flow. Recent progress has improved our understanding of what sets the ... ...

    Abstract Successful management of flooding and erosion hazards on floodplains depends on our ability to predict a river channel's shape and the lifespan during which it will continue to flow. Recent progress has improved our understanding of what sets the lifespan and width of single‐thread channels; the next challenge is to extend this knowledge to braided channels and their interwoven sub‐channels (threads). In this study, we investigate the lifespan and width of braided channel threads in a large experimental data set, coupled with particle‐image velocimetry‐derived measurements of riverbank erosion and accretion. We find that, unlike single‐thread channels, braided channels in the experiment do not exhibit an equilibrium between bank erosion and accretion. Instead, bank erosion outpaces lateral accretion, causing individual threads to widen and infill until they are abandoned. Thread lifespan is limited to the time it takes for threads to triple their width: tripling of the width yields enough bank material to aggrade more than half the channel depth, at which point flow is rerouted to a narrower thread. In consequence the width of active threads is limited to three times their initial width. Threshold channel theory accurately predicts the median thread width, which is roughly double the initial width and two‐thirds the limiting width. The results are consistent with existing field data and suggest that differential bank migration is sufficient to explain why braided channels show greater width variability and higher width‐to‐depth ratios than their single‐thread counterparts.
    Keywords bank erosion ; data collection ; longevity ; research ; rivers ; water
    Language English
    Dates of publication 2022-08
    Publishing place John Wiley & Sons, Ltd
    Document type Article
    Note JOURNAL ARTICLE
    ZDB-ID 5564-5
    ISSN 1944-7973 ; 0043-1397
    ISSN (online) 1944-7973
    ISSN 0043-1397
    DOI 10.1029/2021WR031236
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    In stock of ZB MED Bonn / Germany

    Z 4285: Show issues

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  5. Article: Intercostal chest drains: Are you confident going on the pull? If not use the I-T-U approach.

    Chadwick, A J / Halfyard, R / Ali, M

    Journal of the Intensive Care Society

    2015  Volume 16, Issue 4, Page(s) 312–325

    Abstract: Chest drains are common on intensive care units for a wide variety of clinical conditions. Despite this, there are no published data on their use within the intensive care unit and minimal published literature to guide decision making regarding the ... ...

    Abstract Chest drains are common on intensive care units for a wide variety of clinical conditions. Despite this, there are no published data on their use within the intensive care unit and minimal published literature to guide decision making regarding the timing of their removal. Therefore, we undertook an audit to review our experience over one year, as to the degree of variability in when chest drains were removed. Using our electronic observation records, we assessed the length of stay of our chest drains against their functionality by whether they remained swinging (i.e. in connection with the pleural space) and whether they had a pathological fluid output (>150 mL/24 h). We found that our drains had a mean duration of 5.89 days, and that one-quarter remained in place for three days despite being non-functional. To conclude, we have devised a three-stage assessment (using the acronym I-T-U), to help guide an intensivist in the safe and timely removal of a chest drain.
    Language English
    Publishing date 2015-04-29
    Publishing country England
    Document type Journal Article
    ZDB-ID 2701626-2
    ISSN 1751-1437 ; 1751-1437
    ISSN (online) 1751-1437
    ISSN 1751-1437
    DOI 10.1177/1751143715583856
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  6. Article: Use of a 0.25 per cent fipronil pump spray formulation to treat canine cheyletiellosis.

    Chadwick, A J

    The Journal of small animal practice

    1997  Volume 38, Issue 6, Page(s) 261–262

    Abstract: Two outbreaks of cheyletiellosis are described. In one of the outbreaks, a human member of the household was also affected. A 0.25 per cent fipronil pump spray formulation was applied to the affected and in-contact animals. A permethrin spray was used in ...

    Abstract Two outbreaks of cheyletiellosis are described. In one of the outbreaks, a human member of the household was also affected. A 0.25 per cent fipronil pump spray formulation was applied to the affected and in-contact animals. A permethrin spray was used in an attempt to eliminate environmental contamination. One month later, the affected animals were re-examined. No evidence of Cheyletiella mites could be found. A second application of fipronil was undertaken. No further outbreaks were reported during an eight month follow-up.
    MeSH term(s) Administration, Topical ; Animals ; Dermatitis/drug therapy ; Dermatitis/etiology ; Dermatitis/veterinary ; Dog Diseases/drug therapy ; Dog Diseases/epidemiology ; Dog Diseases/etiology ; Dogs ; Dose-Response Relationship, Drug ; Follow-Up Studies ; Insecticides/administration & dosage ; Insecticides/therapeutic use ; Male ; Mite Infestations/complications ; Mite Infestations/drug therapy ; Mite Infestations/veterinary ; Permethrin ; Pyrazoles/administration & dosage ; Pyrazoles/therapeutic use ; Pyrethrins/administration & dosage ; Pyrethrins/therapeutic use
    Chemical Substances Insecticides ; Pyrazoles ; Pyrethrins ; Permethrin (509F88P9SZ) ; fipronil (QGH063955F)
    Language English
    Publishing date 1997-06
    Publishing country England
    Document type Case Reports ; Journal Article
    ZDB-ID 410743-3
    ISSN 1748-5827 ; 0022-4510 ; 1748-5827
    ISSN (online) 1748-5827
    ISSN 0022-4510 ; 1748-5827
    DOI 10.1111/j.1748-5827.1997.tb03364.x
    Database MEDical Literature Analysis and Retrieval System OnLINE

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    In stock of ZB MED Cologne/Königswinter

    Zs.B 590: Show issues Location:
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  7. Article: Use of a 0.25 per cent fipronil pump spray formulation to treat canine cheyletiellosis

    Chadwick, A.J

    Journal of small animal practice. June 1997. v. 38 (6)

    1997  

    Keywords dogs ; Cheyletia ; mite control ; insecticides ; permethrin ; spraying
    Language English
    Dates of publication 1997-06
    Size p. 261-262.
    Document type Article
    ZDB-ID 410743-3
    ISSN 1748-5827 ; 0022-4510 ; 1748-5827
    ISSN (online) 1748-5827
    ISSN 0022-4510 ; 1748-5827
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    In stock of ZB MED Cologne/Königswinter

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  8. Article: Inversion of the disc and temporal field loss in chronic simple glaucoma.

    Chadwick, A J

    The British journal of ophthalmology

    1968  Volume 52, Issue 12, Page(s) 932–933

    MeSH term(s) Aged ; Chronic Disease ; Female ; Glaucoma/surgery ; Humans ; Nervous System Diseases/complications ; Optic Nerve ; Visual Fields
    Language English
    Publishing date 1968-12
    Publishing country England
    Document type Journal Article
    ZDB-ID 80078-8
    ISSN 1468-2079 ; 0007-1161
    ISSN (online) 1468-2079
    ISSN 0007-1161
    DOI 10.1136/bjo.52.12.932
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  9. Article: UNUSUAL COMPLICATION OF A CHALAZION.

    CHADWICK, A J

    The British journal of ophthalmology

    1963  Volume 47, Page(s) 364

    MeSH term(s) Abscess ; Anti-Bacterial Agents ; Chalazion ; Cysts ; Drug Therapy ; Eye Neoplasms ; Eyelids ; Humans ; Staphylococcal Infections
    Chemical Substances Anti-Bacterial Agents
    Language English
    Publishing date 1963-06
    Publishing country England
    Document type Journal Article
    ZDB-ID 80078-8
    ISSN 1468-2079 ; 0007-1161
    ISSN (online) 1468-2079
    ISSN 0007-1161
    DOI 10.1136/bjo.47.6.364
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  10. Article: Intraocular penetration of the antibiotic fucidin.

    Chadwick, A J / Jackson, B

    The British journal of ophthalmology

    1969  Volume 53, Issue 1, Page(s) 26–29

    MeSH term(s) Aqueous Humor/analysis ; Aqueous Humor/metabolism ; Eye Diseases/drug therapy ; Fusidic Acid/blood ; Fusidic Acid/metabolism ; Fusidic Acid/therapeutic use ; Humans ; Male ; Staphylococcal Infections/drug therapy
    Chemical Substances Fusidic Acid (59XE10C19C)
    Language English
    Publishing date 1969-01
    Publishing country England
    Document type Journal Article
    ZDB-ID 80078-8
    ISSN 1468-2079 ; 0007-1161
    ISSN (online) 1468-2079
    ISSN 0007-1161
    DOI 10.1136/bjo.53.1.26
    Database MEDical Literature Analysis and Retrieval System OnLINE

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