1,790 research outputs found
Modeling Decadal Salt Marsh Development: Variability of the Salt Marsh Edge Under Influence of Waves and Sediment Availability
No full textSalt marshes can contribute to coastal protection, but the magnitude of the protection depends on the width of the marsh. The cross-shore width of the marsh is to a large extent determined by the delicate balance between seaward expansion and landward retreat. The influence of the magnitude of daily occurring mild weather conditions and sediment availability on the variability of salt marsh width has not been systematically assessed. This paper investigates how the magnitude of homogeneous hydrodynamic forcing, combined with sediment availability, affects the biophysical development, and more specifically retreat and expansion of salt marshes. The dynamic extent of the salt marsh is assessed by modeling online-coupled hydrodynamics, morphodynamics and vegetation growth using the numerical Delft3D-Flexible Mesh model, and a vegetation growth module. Simulated patterns around the salt marsh edge resembled field observations, as well as the simulated temporal variability of the lateral position of the salt marsh edge. In the model, the salt marsh extended seaward at low wave forcing (0.00 m; 0.05 m), and retreated landward at higher wave forcing (0.10 m; 0.15 m). With increasing physical stress, the salt marsh edge was found at lower elevations, indicating an unhealthy system with a retreating marsh edge due to vegetation mortality, whereas decreasing physical stresses result in a higher salt marsh edge, enabling expansion. This balance suggests the importance of response time of vegetation to physical stress. Yet, the salt marsh forced with higher waves was able to switch from a retreating extent retrogradational to an expansional behavior as sediment supply increased.Environmental Fluid Mechanic
Going solo or joining someone else’s show: multi-author blogs as a way to maximise your time and exposure
No full textWith the practice of academic blogging becoming increasingly mainstream, it is important to emphasise the diversity of blog formats out there, from personal blogs to multi-author blogs run by institutions or around certain themes. Alex Marsh discusses the differences and finds that the commitment of time and energy associated with an individual blog can be enough to deter some people and that a good way to ease into a new blogging routine is by making occasional contributions to a multi-author blog
RAD 2025: O\u27Shan Waters, Author of _Moments in Time_ with Dr. Michon Benson-Marsh, Moderator
No full textO\u27Shan Waters discusses her award-winning novel Moments in Time with Dr. Michon Benson-Marsh. This book talk concluded RAD 2025: Reimagining the African Diaspora: Preserving and Sharing Our Stories of Labor, Love, Longing, and Belonging, hosted by the College of Liberal Arts and Behavioral Sciences, Texas Southern University, Thursday, February 27, 2025
Steering Taste: Ernest Marsh, a study of private collecting in England in the early 20th Century
No full textThe primary aim of this thesis is to focus attention on the bourgeois, 'un-named' collector. The driving force behind most museum and art gallery collections of the Victorian and Edwardian period. British museum and art gallery records of gifted collections, bequests and loans usually note their donors. However, with a few notable exceptions, little is known about the collectors, their activities and motivation in making such presentations.
Using the interests and activities of the Quaker miller and collector Ernest Marsh (1843-1945) as a case study, this thesis explores how in the period 1890-1945 a collector came to be a key agent in the construction and manifestation of taste in British Applied Arts and to a lesser degree in the Fine Arts. Through primary visual and documentary evidence of the Marsh home, and reference to contemporary and later commentaries it considers the relative influences of husband and wife on decorating and furnishing the domestic interior, the evolution of taste, and, for Ernest Marsh, its impact upon his artistic interests within the public arena.
By examination of private papers, metropolitan and provincial art gallery and museum archives it also considers evidence of the inter-relationships between donors and curators, and the mutual advantages and disadvantages accruing to both, particularly focussing on the processes in bringing about changes in individual and institutional collecting policy. Further, by review of records of, in particular, the Contemporary Art Society and the Greenslade archive, it examines the degree to which private benefactors and those in public or semi-public office, acting as fund-raisers and spenders exercise influence through patronage of particular practitioners, choice of works and initiating new designs
Bio-physical controls on tidal network geomorphology
No full textThe copyright of this thesis rests with the author and no quotation from it or information derived from it may be published without the prior written consent of the authorLooking over a tidal wetland, the tidal network characterised by its intricate system
of bifurcating, blind-ended tidal courses clearly stands out from the overall landscape.
This tidal landform exerts a fundamental control on the morphology and ecology within
the tidal environment. With today’s recognition of the ecological, economical and
societal values provided by tidal wetlands, which has been notably reflected in the
development of restoration management strategies across Europe and USA, there is
a need to fully understand the nature and development of tidal networks as well as
their relationships with associated landforms and biotic components (e.g. vegetation),
to eventually guarantee the success of current and future restoration practices. Accordingly,
this research aims to bring further insights into the bio-physical controls on
the geomorphology of tidal networks. To this end, a combination of remote sensing,
modelling and field activities was employed.
A geo-spatial analysis was performed at Queen Mary, University of London (UK), to
address the variability of tidal network patterns. A series of network scale morphometric
variables was extracted using airborne LiDAR data among selected tidal networks
across the UK depicting different planview morphologies, and supplemented with
the collection of corresponding marsh scale environmental variables from published
sources. Multivariate statistics were then performed to characterise the variability of
tidal network patterns and identify the inherent environmental controls. The analysis
has revealed that every network type can be characterised based upon measures of
network size and complexity, with each network pattern depicting proper morphometric
aspects. Particularly, the stream Strahler order and the median depth of the network
main channel have the highest discriminating weight on the patterns investigated. High
correlation between the latter variable and network main channel width has revealed
that linear, linear-dendritic and dendritic networks followed a transitional gradient in
their aspect ratio approximated by a power law and thus are seen to depict similar
erosional processes. To the contrary, meandering networks clearly depart from this relationship, and show particular segregation in their aspect ratios with respect to
dendritic networks. Globally, differentiation on network morphometric properties has
been linked to environmental conditions specific to the marsh physiographic setting
within which a tidal network develops. Conceptually, tidal networks seem to adapt to
marsh environmental conditions by adopting suitable morphologies to drain their tidal
basin effectively.
An eco-geomorphic modelling framework was developed at University of Trento
(Italy), to address tidal network morphological development. In line with current
theories as well as modelling advances and challenges in the field of tidal network
ontogeny, emphasis was thus placed on the investigation of tidal channel formation
and evolution in progressive marsh accretional context. Under these environmental
conditions, tidal network development can be ascribed to the combination of two
channel-forming processes: channel initiation results from bottom incisions in regions
where topographic depressions occur; channel elaboration results from differential
deposition, contributing to the deepening of the tidal channels relative to the adjacent
marsh platform. Further evolutionary stages including channel reduction proceed from
the horizontal progradation of the marsh platform which may lead eventually to channel
infilling. Moreover, both qualitative and quantitative results allude to an acceleration of
the morphological development of the synthetic tidal networks with increasing sediment
supply. These different observations thus emphasise the prevalence of depositional
processes in shaping tidal channels. In a second stage, the investigation was extended
to the role of the initial tidal flat morphology as an inherent control on tidal network
development, by considering different scenarios of topographic perturbations, which
has revealed its legacy on tidal network morphological features. Modelling experiments
have also acknowledged salt marsh macrophytes as a potential control on network
evolution depending on their biomass distribution within the tidal frame. However,
tidal channel morphodynamcis appears to be sensitive to the way biomass growth is
mathematically parameterised in the model.
In view of the current challenges in transcribing mathematically such a dynamic
process and the relevance of bio-physical interactions in driving salt marsh and tidal
network evolution, a field survey was conducted in a temperate salt marsh in the
Netherlands, as part of the mobility to UNESCO-IHE (Netherlands) in partnership with
University of Antwerp (Belgium), to assess vegetation distribution and productivity in
the tidal frame. Particularly, emphasis was placed on extending investigations on the possible presence of relationships involving vegetation properties in different climatic and ecological conditions from those characterising these previously documented
relationships. Regression analysis has revealed that biomass growth can be expressed
as a linear function of marsh relative elevation, providing therefore direct empirical
validation for corresponding assumptions reported in the literature and used in the
present modelling framework; surprisingly, that increase did not correlate with an
increase in species richness and diversity. Analysis of likely associations between
vegetation morphometrics and total standing biomass yielded only a single linear
relationship linking the latter variable to stem height. In truth, these observations may
bear reconsiderations on the global validity of the assumptions used in the formulation of some eco-geomorphic processes which are applied in the study and prediction of
wetland resiliency facing climate change
The Smoke Factor: Things you Should Know
No full text Surgical smoke is a regular hazard that the majority of perioperative personnel are exposed to. Many staff are unaware of the risks of surgical smoke and many more may take it for granted that a surgical facemask provides enough protection. This article provides detail on the composition of surgical smoke and highlights the potential dangers that theatre staff face and what could be done to protect them. It will demonstrate the potential harm for the patient with particular reference to laparoscopic procedures as these are becoming more favourable in general and gynaecological specialities and are of particular interest to the author. </jats:p
Spirit of Talk Talk
No full textSpirit of Talk Talk is a finely crafted and lavishly produced book celebrating the music created by Talk Talk and illustrated with a treasure trove of images from long-time collaborator and renowned art designer James Marsh. Displayed alongside large original artworks and previously unseen sketches and alternative covers, are rare and previously unseen photographs of the band and a specially commissioned biography of Talk Talk by music journalist and author Chris Roberts. Photographic images have been supplied from the archives of photography luminaries Lawrence Watson, Richard Haughton and Sheila Rock amongst others. The book includes the full transcript of Mark Hollis's final interview about the band and numerous tributes and eulogies from musicians, artists, producers, and people who worked with the band and knew them intimately. There are also honest, touching, and revealing tributes from musicians, artists friends and fans who were, and continue to be, influenced by Talk Talk's music
Wave Attenuation by Global Coastal Salt Marsh Habitats
No full textIn this study, a numerical model (XBeach-vegetation) and statistical Bayesian Network (Netica) was developed for the simulation and quantification of wave attenuation for various combinations of global salt marsh characteristics and extreme hydraulic conditions. The purpose of this modeling effort was to test the ability of the numerical model and statistical model in properly simulating salt marsh-hydraulic interactions which occur around the world. Additionally, testing of the ability of this model to quantify wave attenuation over salt marsh habitats while under extreme hydraulic conditions (high wave heights and water levels) was performed. First, the numerical model was calibrated, tested, and validated based on both a field and flume study which measured wave attenuation over natural salt marsh. Next, the numerical model was used to produce many results for wave heights at various locations over a salt marsh platform. These results produced a dataset which was input into a Bayesian Network (BN) for further organization and quantification of wave attenuation by global salt marshes. Finally, the salt marsh components were tested for their influence on the BN, and the results were compared to the Xbeach-vegetation results for several cases in order to provide an example of how each method produces results. Initially, the numerical model was calibrated and validated based on wave data which was provided by members of the BE SAFE study and was recorded during a winter storm in 2015 at Hellegat Polder, Western Scheldt, the Netherlands. The numerical model simulated the recorded wave heights accurately, and proved to be effective in reproducing results for extreme hydraulic conditions recorded at Hellegat. Additionally, the numerical model was tested on the conditions of the Hannover wave flume study, which generated extreme waves in one of the largest wave flumes around the world, in order to measure wave attenuation by a 40 meter section of natural salt marsh at the end of the flume. Once the model was calibrated and validated, the set-up for a batch of numerical model simulations took place. In order to assign inputs which were representative of global coastal salt marsh habitats, data was collected from many sources to form a database. Next, the numerical model was set-up in order to simulate waves occurring over an arbitrary salt marsh platform for many different salt marsh characteristics and hydraulic conditions. Wave heights were obtained at five distances across the salt marsh platform, and the results were input into a BN for further data handling. The BN (Netica) was used to structure and organize the data into a compiled network, which was completed before the network could be used further. Once the network was compiled, the various salt marsh characteristics and hydraulic conditions were varied within the network in order to see which characteristics and conditions were most likely to produce certain wave heights at various distances throughout the salt marsh platform. The influence of each characteristic and parameter could additionally be quantified in a probabilistic manner using the network. In selecting the various values within each node of the BN separately, an assessment could be performed in order to see the influence of each salt marsh component on the resulting wave heights. The results produced by both the Netica program and the Xbeach-vegetation model were presented in order to show a comparison of how each method presents the results. Finally, a sensitivity analysis of the various salt marsh characteristics was performed to obtain knowledge on how these components influenced resulting wave heights. Once all of this was completed, conclusions were made based on the results, and recommendations were provided for the improvement of future research efforts within this field.Civil Engineering and GeosciencesHydraulic EngineeringCoME
An investigation on salt marsh resilience to sea-level rise and increased storm intensity
No full textSalt marshes are ecosystems with significant economic and environmental value. They provide numerous services, including nutrient removal, habitat provision and carbon sequestration (Barbier et al., 2011). They are also widely recognised as nature-based solutions for coastal defence due to their ability to buffer storm waves (Leonardi et al., 2018). However, it is still unclear how the combined impact of future sea-level rise and possible increases in storm intensity will affect salt marsh resilience (Schuerch et al. 2013). It has been observed that salt marshes can survive sea-level rise if sediment supply and organogenic production are high enough to allow marsh accretion (Kirwan et al., 2010, 2016). However, increasing rates of sea-level rise can lead to marsh drowning by increasing the accommodation space and the amount of sediment inputs required for marsh stability (Kirwan et al., 2010; Ganju et al., 2017). Marsh degradation can also be caused by lateral erosion triggered by wind waves, such as the ones generated during storms (Leonardi et al., 2016; Li et al., 2019). However, several studies have showed that, on the other hand, overwash by storm surges can support marsh resilience by delivering significant amount of sediment to marsh platforms (Walters and Kirwan, 2016; Castagno et al., 2018). This study investigates marsh resilience under the combined impact of various storm surge and sea-level scenarios by using a sediment budget approach. The current paradigm is that a positive sediment budget supports the survival and accretion of salt marshes, while a negative sediment budget causes marsh degradation (Ganju et al. 2015). The Ribble Estuary, North-West England, was used as a case study
Salt marsh establishment in poorly consolidated muddy systems: effects of surface drainage, elevation, and plant age
No full textConservation and restoration of salt marsh ecosystems are becoming increasingly important because of the many ecosystem services they provide. However, the processes controlling salt marsh establishment and persistence, especially on bare tidal flats in muddy areas, remain unclear. As muddy sediments typically experience a restriction of soil drainage, we expect that a surface drainage relief due to a heterogeneity topography, as might occur on the edge of tidal channels, can facilitate the establishment of salt marsh vegetation on muddy tidal flats. By means of a manipulative field experiment, using “Mega-Marsh Organ” mesocosms, we investigated the impact of surface drainage and elevation relative to mean sea level on (1) the survival of Spartina anglica seedlings from three different age classes: 1-yr, 3-month, and 1-week; and (2) the growth performance of mature S. anglica marsh tussocks. S. anglica seedling survival, especially in the establishment phase, was positively affected by better surface drainage, increases of seedling age, and higher elevation relative to mean sea level. That is, the survival rate of S. anglica seedlings at the end of 6th week increased from 0% (at surface water undrained, 1-week, 0 cm elevation) to 94.44% (at surface water drained, 1-yr, 90 cm elevation). In contrast, surface drainage did not affect the performance of large S. anglica marsh tussocks, as only increased elevation relative to mean sea level was shown to affect S. anglica tussock growth in terms of plant height, shoot numbers, and dry biomass. Based on our findings, we proposed a conceptual model to understand how surface drainage-driven feedbacks in a heterogeneous topography may be reinforced to induce salt marsh establishment in muddy systems. Further testing of present hypothesized model would be beneficial for insights into salt marsh establishment on tidal mudflats.Hydraulic Engineerin
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