A comparison of landslide rates following helicopter and conventional cable-based clear-cut logging operations in the Southwest Coast Mountains of British Columbia

A comparison of landslide rates following helicopter and conventional, cable-based, clear-cut logging was carried out using results from two independent terrain attribute studies in the Eldred and Lois River watersheds in the Southwest Coast Mountains of British Columbia. Landslides initiating from directly within a road prism were excluded from the study in order to focus the comparison on landslides related primarily to conventional versus helicopter yarding methods. A landslide rate of 0.02 landslides/ha was observed in 162 terrain polygons logged by helicopter 8 years prior to this study. Landslide rates in 38 gullied polygons were 0.06 landslides/ha. No landslides were observed in 124 open-slope polygons. Over a similar 8-year average period, 0.03 landslides/ha were observed in 142 cable-yarded terrain polygons; 0.06 and 0.02 landslides/ha occurred in gullied and open-slope polygons, respectively. t-Tests indicate that total landslide rates are not significantly different following helicopter and conventional logging; however, a dichotomy exists between gullied and open-slope terrain polygons. Landslide rates are not significantly different in gullied terrain but are significantly higher on open-slopes following conventional cable logging. Consequently, landslides appear to have a greater potential to occur in open-slope terrain following conventional logging, but differences in gullied polygons are less likely. Increased post-logging landslide rates in conventionally logged, open slopes are more likely the result of undetected road-related drainage changes than differences between helicopter and conventional yarding-related ground disturbance.     

Season of MIST

Neil Arnold reports from the Autumn MIST Meeting held on 24 November 2000 at Burlington House, where discussion included a new electronic initiative that could improve access to solar–terrestrial data across the country.     

A global model or a scaled-down version?: geographies of convergence and divergence in the Australian retail banking sector

Via the spread of financial liberalisation and deregulation across advanced industrialised societies over the past two decades, national banking sectors have come under increased competitive pressure. In Australia, this pressure has manifested itself in two main forms: an almost self-imposed nervousness over the growing scale and rapidity of bank mergers occurring at an international level; and the growth of new cut-price competitors in the domestic retail market. There is now growing evidence of convergence between national banking sectors in key areas. This paper employs four criteria to examine the degree of convergence between the Australian retail banking sector and its international counterparts: centralisation of services and operations; application of the `user pays' philosophy to services; a `flight to quality' in lending and service provision; and industrial relations practices. While considerable similarities can be found between the Australian retail banking sector and its international comparators at the macro-level of analysis, there is also substantial diversity evident at regional and local scales as new public- and private-sector agencies and institutions seek to meet the financial needs of those individuals and communities effectively disenfranchised from the banking system via the major banks' `world's best practice' management strategies. The paper argues that a critical and reflexive concept of scale is imperative in apprehending the increasingly complex ways in which financial service provision is being reconfigured by the strategies of reaction and resistance employed by financial consumers, urban and rural local governments, national and state media, financial consumer agencies and State and Federal Governments.     

Sudoite in the Archaean Witwatersrand Basin

Sudoite, with almost ideal composition of Mg₂Al₄Si₃O₁₀(OH)₈, has been found in the Khaki shale of the Witwatersrand Basin, South Africa. The sudoite occurs in aggregates of elongate bundles alternating with muscovite and rarely pyrophyllite, in an assemblage of sudoite-pyrophyllite-muscovite-quartz-rutile-pyrite. The stability of sudoite is attributed to a particularly Mg rich bulk rock composition, elevated sulphur activity, and metamorphic conditions just above the kaolinite to pyrophyllite transition. Nearby low variance chlorite, chloritoid-and pyrophyllite-bearing assemblages represent differing bulk rock compositions at potentially very similar metamorphic conditions. As the first find of sudoite in the Archaean, this occurrence in the Witwatersrand Basin extends the metamorphic setting and age in which sudoite is found to well beyond Phanerozoic belts of crustal thickening.     

Uranium-Series Ages of Travertines and Timing of the Last Glaciation in the Northern Yellowstone Area, Wyoming-Montana

Uranium-series age determinations by mass spectrometric methods were done for travertines and associated carbonate veins related to clastic deposits of the last glaciation (Pinedale) in the northern Yellowstone area. Dramatic variations in the hydrologic head are inferred from variations in the elevation of travertine deposition with time and are consistent with the expected hydrologic effects of glaciation. We determine the following chronology of the Pinedale Glaciation, with the key assumption that travertine deposits (and associated carbonate veins) perched high above present thermal springs were deposited when glaciers filled the valley below these perched deposits: (1) the early Pinedale outlet glacier advanced well downvalley between 47,000 and 34,000 yr B.P.; (2) the outlet glacier receded to an interstadial position between 34,000 and 30,000 yr B.P.; (3) an extensive Pinedale ice advance occurred between 30,000 and 22,500 yr B.P.; (4) a major recession occurred between 22,500 and 19,500 yr B.P.; (5) a minor readvance (Deckard Flats) culminated after 19,500 yr B.P.; and (6) recession from the Deckard Flats position was completed before 15,500 yr B.P. This chronology is consistent with the general trend of climatic changes in the northern hemisphere as revealed by recent high-resolution ice-core records from the Greenland ice sheet.     

The rotation of garnet porphyroblasts around a single fold, Lukmanier Pass, Central Alps

The orientation of the straight internal foliation S_i within large ( 5 mm) garnet porphyroblasts has been measured relative to the orientation of the external foliation S_e around a single antiform of 0.5 m wavelength, which folds the dominant regional foliation. The internal foliation is not constant in orientation, but varies consistently both with position around the fold and with the porphyroblast ellipticity. The dip of S_i (hinge dip taken as zero) is consistently less than the dip of S_e; it increases with increasing dip of S_e and with increasing ellipticity of the porphyroblasts. S_i effectively defines a fold with an opening angle greater than that in the external foliation. The opening angle of this fold in S_i decreases with increasing porphyroblast ellipticity. The observed variation in the orientation of S_i can be explained qualitatively by a flattened flexural flow model for fold development, as could be expected for folding of a pre-existing, strongly anisotropic foliation. The measurements clearly demonstrate that rotation of porphyroblasts relative to geographical co-ordinates did occur during the development of this fold and that a model based on the classical theories of rotation of stiff inclusions in a weaker viscous matrix is most appropriate.     

A note on further refinements to a procedure for the extraction of carbonaceous fly-ash particles from sediments

This paper describes improvements to a previously published technique for the extraction of carbonaceous fly-ash particles from sediments. By using test-tubes in a water-bath rather than beakers on a hot-plate, the number of simultaneous preparations that can be done is increased and the length of time spent on the preparations and the amounts of hazardous chemicals used is reduced. As the digestion vessel remains the same throughout the procedure, potential loss of particles due to transfer of material between vessels is also minimised, whilst keeping sensitivity, accuracy and detection limit the same.