Treating the Risks in Cairns

Cairns is exposed to the well-known natural hazards oftropical cyclone, flood, stormsurge and thunderstorm, but is also exposed to thelesser-known hazards of landslip, earthquake and dam break flooding. Recommendations fortreating the risks associated with these hazards have been made that will involve amulti-disciplinary approach to treatment strategies, require the cooperation of allthree levels of government, involve public utility authorities and private enterprise andinvolve the community as a whole.This paper summarises the suggested mitigation treatmentoptions, presented to the Cairns City Council and identified in the LocalGovernment Disaster Mitigation Project conducted in Cairns in 1999/2000 by theQueensland Department of Emergency Services.     

Quantifying Storm Tide Risk in Cairns

The United Nations International Decade for Natural Disaster Reduction (IDNDR)gave rise to an increasing level of attention to the risks posed by a range of naturalhazards and the development of strategies by which to reduce those risks. It waswidely recognised that in order to evaluate risk treatment strategies it was necessaryto `measure' the level of risk that already existed and the level of risk that would beencountered with the treatment strategy(s) in place.This paper outlines the methodology developed under the AGSO (now GeoscienceAustralia) Cities Project to quantify the risk associated with storm tide inundation. It includes the methodology for `measuring' the level of community exposure to storm tide hazards and the methodology for `measuring' community vulnerability. The Far North Queensland city of Cairns is used as the case study to demonstrate the application of these methods.     

Curved scanline theory

This work develops the theory of measuring fracture frequency with curved scanlines, as a direct development of work done by others on straight scanlines. Various possible shapes for curved scanlines range between triangular and rectangular, with circular as a reasonable preliminary selection. The discrepancy among different selections decreases with increasing roughness amplitude of the scanline. Analytic solutions for average fracture frequency are given for circular scanlines through single and multiple fracture sets. Results for single fracture sets are plotted. The analytic solution for the general situation of any shape scanline through multiple fracture sets is given. Analytic solutions are given and plotted for circular scanlines through a fracture fabric ellipsoid. A circular scanline spanning 180 degrees yields a global fracture frequency of statistical significance.     

Radiometric characteristics of heavy mineral deposits along the west coast of South Africa

During the last decade, exploration and mining of modern-Tertiary heavy mineral beach and raised beach sands along the west coast of South Africa has developed into a major industry. High resolution radiometric techniques have demonstrated their use as a quantitative indicator of total heavy mineral concentration (THM) and also have the ability to discriminate between sediments derived from different provenance terrains. Results indicate that it is possible to calculate the total heavy mineral concentration from high resolution radiometric measurements, but the ability to quantify the concentration of individual mineral fractions, such as ilmenite, requires further refinement of the method. Radiometric characteristics of the light mineral fraction made it possible to distinguish between sediments from mixed marine-aeolian palaeoplacers and active present beach placers. The effects of in situ alteration of the ilmenite fraction in the palaeoplacers were also reflected by subtle contrasts in the radiometric character of the deposits. Furthermore, the uniform radiometric character of the sample population indicates a common provenance for the heavy mineral suite and supports previous results which indicate the metamorphites of the mid-Proterozoic Namaqua Province as the primary source terrain. The high resolution radiometric techniques discussed offer a broad spectrum of applications in sedimentology and have the potential to aid heavy mineral exploration. With further refinement it can possibly be used quantitatively in grade control during mining and beneficiation of heavy mineral deposits. Received: 19 July 1996 / Accepted: 7 January 1997     

Overburden deformation associated with halokinesis in the Southern North Sea: implications for the origin of the Silverpit Crater

Gravitational collapse in response to the creation of salt swells and diapirs is a common phenomenon within regions such as the Southern North Sea. Although collapse faulting and slumping of linear salt swell flanks has previously been documented, the existence of concentric collapse structures surrounding diapirs and isolated salt lows is a recently recognised feature. 3-D seismic data from the Southern North Sea demonstrates that concentric collapse faulting around both diapirs and subcircular salt lows is common. The recognition of concentric collapse structures formed in response to salt withdrawal, and adjacent inflation, provides an alternative mechanism for the origin of the proposed Silverpit impact crater.     

Glacial conditions that contribute to the regeneration of Fountain Glacier proglacial icing,Bylot Island,Canada

Proglacial icings are one of the most common forms of extrusive ice found in the Canadian Arctic. However, the icing adjacent to Fountain Glacier, Bylot Island, is unique due to its annual cycle of growth and decay, and perennial existence without involving freezing point depression of water due to chemical characteristics. Its regeneration depends on the availability of subglacial water and on the balance between ice accretion and hydro‐thermal erosion. The storage and conduction of the glacial meltwater involved in the accretion of the icing were analyzed by conducting topographic and ground penetrating radar surveys in addition to the modelling of the subglacial drainage network and the thermal characteristics of the glacier base. The reflection power analysis of the geophysical data shows that some areas of the lower ablation zone have a high accumulation of liquid water, particularly beneath the centre part of the glacier along the main supraglacial stream. A dielectric permittivity model of the glacier – sediment interface suggests that a considerable portion of the glacier is warm based; allowing water to flow through unfrozen subglacial sediments towards the proglacial outwash plain. All these glacier‐related characteristics contribute to the annual regeneration of the proglacial icing and allow for portions of the icing to be perennial. Copyright © 2013 John Wiley & Sons, Ltd.