The interplay between extrinsic and intrinsic controls in determining floodplain wetland characteristics in the South African drylands

Controls on the characteristics of floodplain wetlands in drylands are diverse and may include extrinsic factors such as tectonic activity, lithology and climate, and intrinsic thresholds of channel change. Correct analysis of the interplay between these controls is important for assessing possible channel–floodplain responses to changing environmental conditions. Using analysis of aerial imagery, geological maps and field data, this paper investigates floodplain wetland characteristics in the Tshwane and Pienaars catchments, northern South Africa, and combines the findings with previous research to develop a new conceptual model highlighting the influence of variations in aridity on flow, sediment transport, and channel–floodplain morphology. The Tshwane–Pienaars floodplain wetlands have formed in response to a complex interplay between climatic, lithological, and intrinsic controls. In this semi‐arid setting, net aggradation (alluvium >7 m thick) in the wetlands is promoted by marked downstream declines in discharge and stream power that are related to transmission losses and declining downstream gradients. Consideration of the Tshwane–Pienaars wetlands in their broader catchment and regional context highlights the key influence of climate, and demonstrates how floodplain wetland characteristics vary along a subhumid to semi‐arid climatic gradient. Increasing aridity tends to be associated with a reduction in the ability of rivers to maintain through‐going channels and an increase in the propensity for channel breakdown and floodout formation. Understanding the interplay between climate, hydrology and geomorphology may help to anticipate and manage pathways of floodplain wetland development under future drier, more variable climates, both in South African and other drylands. Copyright © 2016 John Wiley & Sons, Ltd.     

Safeguarding coastal coral communities on the central Great Barrier Reef (Australia) against climate change: realizable local and global actions

The threats of wide-scale coral bleaching and reef demise associated with anthropogenic (global) climate change are widely known. Less well considered is the contributing role of conditions local to the reef, in particular reef water quality, in co-determining the physiological tolerance of corals to increasing sea temperatures and declining pH. Here, the modelled benefit of reduced exposure to dissolved inorganic nitrogen (DIN) in terrestrial runoff, which raises the thermal tolerance of coastal coral communities on the central Great Barrier Reef (Australia), is considered alongside alternative future warming scenarios. The simulations highlight that an 80% reduction in DIN ‘buys’ an additional ~50–60?years of reef-building capacity for No Mitigation (‘business-as-usual’) bleaching projections. Moreover, the integrated management benefits provided by: (i) local reductions of ~50% in DIN contained in river loads, and (ii) global stabilisation of atmospheric CO₂ below 450?ppm can help ensure the persistence of hard-coral-dominated reefscapes beyond 2100. The simulations reinforce the message that beyond the global imperative to mitigate future atmospheric CO₂ emissions there still remains the need for effective local management actions that enhance the resistance and resilience of coral reef communities to the impacts of climate change.     

Development of an urban landslide cellular automata model: a case study of North Vancouver, Canada

Many GIS-based landslide models require detailed datasets that are ideally collected from field measurements, which can incur high costs for carrying out surveys. Even when the data is on hand, implementing physics-based slope stability techniques can be difficult. Common research practice uses differential equations to characterize the dynamic flow of a landslide, but it is often laborious without making substantial simplifications. A possible solution is to implement a cellular automata modeling approach, which represents both spatial and temporal components, to simulate the dynamics of the landslide propagation process. In this study, a simplified cellular automata model is developed for the effective prediction of landslide runouts, where the data requirement is a high resolution digital elevation model (DEM). Parameters, such as slope and slope curvature features, are derived from the DEM and coupled with logistic regression. The developed model is implemented on the Patrick and Dawson-Chu Slide in North Vancouver, Canada. The results from this study site were favorable, given almost 90% agreement between simulated landslides and data obtained for real landslides. In addition, sensitivity analysis was performed on the initiation sites to test the model logic and outputs of the landslide flow.     

The Spey Bay geomorphological study

The Spey Bay coastline and the estuary of the River Spey exhibit a rapidly evolving planform. They provide an opportunity to study geomorphological changes in a coupled coastal/estuarine system which can be measured over hours and days rather than the years and decades associated with more slowly evolving landscape features. Attempting to understand coastal and estuarine geomorphology provides engineers and earth scientists with an exciting intellectual challenge. This is not, however, simply an academic challenge because the successful management of coastal and estuarine environments depends on improving this understanding. The impetus behind our work in this area is the protection of land-use interests. It is in this context that Babtie Dobbie Limited have been employed in studying the River Spey since 1962. This paper is based on a practical case study performed for coastal and river engineering purposes between 1990 and 1992. The case study was formulated using the results and conclusions of earlier geomorphological studies of the area undertaken over the past 32 years. Knowledge gained from previous studies was crucial in designing the detailed methods and techniques employed in the 1990–1992 geomorphological study. Methods used included historical analyses, photogrammetry, numerical modelling, geographic information systems (GIS) and interpretation of the complex processes which drive landform changes in the estuary and along the adjacent shoreline. The improved understanding of geomorphological processes that has been achieved has enabled engineers to formulate a new management strategy. Central to this strategy are engineering solutions to river and coastal stability and flooding problems which are in sympathy with the environment and which take maximum advantage of our understanding of geomorphological processes.     

Stratigraphy and evolution of basalts in Mare Humorum and southeastern Procellarum

Abstract— We have studied the mare basalts of Mare Humorum and southeastern Procellarum (30°W–50°W, 0°–40°S). One hundred and nine basaltic units have been identified from differences in their FeO wt% and TiO₂ wt% content, and variations in crater densities. Crater counting and reference to isotopically dated Apollo samples have provided an age for 33 major units. Some evidence for three distinct periods of volcanic activity has been found. We found that the large unit in the middle of Mare Humorum is the oldest in the basin. This supports the suggestion that the oldest central unit sank causing the lithosphere to bend and create dykes through which lava flowed to produce the outer units. No evidence of a trend in FeO wt% and TiO₂ wt% content against time is found within Mare Humorum. There appears to be no lateral trend of basalts in terms of FeO and TiO₂ wt% over the entire area with time. An increase in FeO content with time is found in the 33 major units and there is some evidence for an increase in TiO₂ in the same units. A correlation between FeO wt% and TiO₂ wt% content is evident when all 109 units are compared. A notable feature of this correlation is a sharp increase in gradient of TiO₂ wt% content when the FeO wt% content rises above about 17%.     

Making “Unofficial” Sacred Space: Spirit Mediums and House Temples in Singapore

Although there has been significant work done on the creation of sacred space in residential housing, not enough attention has been paid to a particular segment of Chinese religion leadership in Singapore – spirit mediums – and the processes in which they practice within the political ideology of the modernist Singaporean state. In this paper, I will show how spirit mediums operate within “unofficially sacred” spaces, specifically house temples that subvert and resist functionalist policies of the Singapore state. Using two visually focussed, participant‐observation case studies, I will argue that this subversion is sustained in two inter‐related ways—one, through the visual comportment of the spirit medium's body through behavior and aesthetic markers and two, through the social prominence of the spirit medium when he or she is in a trance. These two factors come together to temporally displace the importance of the physical location, allowing a spirit medium to operate in any location, “official” or “unofficial.”     

Cavities in the reefs of the Wenlock Limestone (Mid-Silurian) of Shropshire,England

Studies of the growth attitudes and internal structure of organisms in the Wenlock reefs show that cavities existed during reef growth between knobs of reef builders, between individual reef builders, between the branches of reef builders and within skeletons. Only the well sealed growth cavities escaped fill by particulate sediment on burial. The location and nature of diagenetic cavities are governed by the growth fabric of the reefs. Diagenetic cavities were formed by the dislocation of reef components during compaction and by dissolution of organisms, particularly bryozoans, that neighboured growth cavities.

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Zusammenfassung Studien der Wuchsformen und des inneren Baues von Organismen der Wenlock-Riffe zeigen, daß Hohlräume während des Riffwachstums zwischen einzelnen Riffstöcken, zwischen individuellen Kolonien sowie zwischen dem Gerüst und im Inneren der Skelette von Riffbildnern vorhanden waren. Nur vollkommen abgeschlossene, konstruktive Hohlräume sind während der Sedimentation in den Riffen nicht mit Ablagerungen gefüllt worden. Die Lage und Natur diagenetischer Hohlräume werden von den Wuchsformen der Riffe bestimmt. Hohlräume entstehen während der Diagenese durch Verlagerung von Komponenten im Gefolge von Kompaktion und durch Lösung des organischen Karbonatgerüstes; hier werden besonders Bryozoenskelette aufgelöst, die an bestehende Hohlräume angrenzen.

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Résumé Des études de positions d'accroissement et de structures intérieures des organismes dans les récifs de Wenlock montrent que des cavités existaient pendant l'accroissement du récif entre les bosses des pinacles coralliens, entre les pinacles coralliens individuels, entre les branches des pinacles coralliens et à l'intérieur des squelettes. Seules les cavités tout à fait fermées pendant l'accroissement ne furent pas comblées de sédiments détritiques lors de l'ensevelissement. La situation et la nature des cavités diagénétiques sont gouvernées par la structure des récifs. Des cavités diagénétiques furent formées par la dislocation des parties constituentes du récif pendant le tassement et par la dissolution des organismes, en particulier des bryozoaines qui bordaient les cavités formées pendant l'accroissement.

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Comparing the theoretical versions of the Beaufort scale, the T-Scale and the Fujita scale

2005 is the bicentenary of the Beaufort Scale and its wind-speed codes: the marine version in 1805 and the land version later. In the 1920s when anemometers had come into general use, the Beaufort Scale was quantified by a formula based on experiment. In the early 1970s two tornado wind-speed scales were proposed: (1) an International T-Scale based on the Beaufort Scale; and (2) Fujita's damage scale developed for North America. The International Beaufort Scale and the T-Scale share a common root in having an integral theoretical relationship with an established scientific basis, whereas Fujita's Scale introduces criteria that make its intensities non-integral with Beaufort. Forces on the T-Scale, where T stands for Tornado force, span the range 0 to 10 which is highly useful world wide. The shorter range of Fujita's Scale (0 to 5) is acceptable for American use but less convenient elsewhere. To illustrate the simplicity of the decimal T-Scale, mean hurricane wind speed of Beaufort 12 is T2 on the T-Scale but F1.121 on the F-Scale; while a tornado wind speed of T9 (= B26) becomes F4.761. However, the three wind scales can be uni-fied by either making F-Scale numbers exactly half the magnitude of T-Scale numbers [i.e. F′half = T / 2 = (B / 4) − 4] or by doubling the numbers of this revised version to give integral equivalence with the T-Scale. The result is a decimal formula F′double = T = (B / 2) − 4 named the TF-Scale where TF stands for Tornado Force. This harmonious 10-digit scale has all the criteria needed for world-wide practical effectiveness.     

Some geophysical aspects of deep-sea drilling

More than 300 locations covering all the major ocean basins of the world, except the Arctic, have now been explored by deep-sea drilling. Results from deep-sea drilling permit the accurate calibration of seismic reflection profiles but at the same time emphasize the need for caution in interpreting the stratigraphic significance of such records. Basement ages determined from core samples are in close agreement with ages predicted by the concept of sea floor spreading, demonstrating both the validity of that concept and the validity of the paleomagnetic time scale. There also appears to be a demonstrable relationship between the age of the sea floor and its present depth. at many locations permits the documentation of changes in ocean currents, surface and bottom water temperatures, climate, and water depth.