River metamorphosis and environmental change in the Macdonald Valley,New South Wales,since 1949

A significant metamorphosis of channel form occurred on the lower Macdonald River between 1949 and 1955; width and width-depth ratio increased and depth, sinuosity and weighted mean per cent silt-clay in the channel perimeter decreased. The channel has remained unstable since 1955, exhibiting frequent variations in bed elevation and a recent period of minor channel contraction followed by slight enlargement. Since 1946 there has been an increase in summer and annual rainfall and an abrupt, upward shift of the annual series flood frequency curve. As a result an increased proportion of the total sediment load of the river is now being transported as bed-material load. The change in sediment load is a result of greater stream competence and the consequent reworking of sandy sediment temporarily stored within the channel as benches. The observed channel changes are a quasi-adjustment to the increased flood and bed-material load discharges.     

Potential impacts of sand and gravel extraction on the Hunter River,New South Wales

A number of investigations have been undertaken by the New South Wales Water Resources Commission to determine the regional and compound effects of large scale extractive industries on the stability of the Hunter River, New South Wales. Sedimentologic studies of bed material suggest that the Hunter River upstream of Denman has an armoured gravel bed that is immobile during regulated releases from Glenbawn Dam but is disrupted by moderate but less than bankfull flows. Annual bedloadyields have been computed by the bedload rating-flow duration technique for five river gauging stations. Approximate sand and gravel budgets for selected reaches of the Hunter River demonstrate that the present annual extraction rate from temporary sediment storages within the channel greatly exceeds the transport rate upstream of Denman and is approximately equal to the transport rate downstream of Denman. River degradation is imminent if extractive industries continue operating in the channel of the Hunter River     

Mean airstreams of Australia

Streamline analyses of mean monthly resultant surface winds over Australia are presented. Mean confluences represent either cyclone trajectories, or modal fronts. These analyses suggest that Australia's annual airstream climate is of two regimes: that of September to March inclusive, and April to August inclusive. The winter half-year is exemplified by a continental airstream source in southern Australia which diverges over virtually the entire continent. It continues into September and October, although dominating only the southern third to half of Australia, and is absent from November to March. During the summer half-year a new pattern emerges, with three maritime air stream sources represented over the continent: first, air from the Southern Ocean penetrates the south coast reaching its furthest northward extension from December to March inclusive; a second source originating over the Pacific Ocean dominates eastern and northern Australia; and a monsoon source originating over the Indian Ocean which flows overland affecting northern Western Australia. Two modal confluences are noted, one over northwestern Australia from November-February separating monsoon flow from that emanating from the east, and another extending from the west central coast east-southeastward to the southeast coast from November-March separating Southern Ocean air from that originating over the Pacific Ocean.     

Morphological Impacts and Implications of a Trial Release on the Wingecarribee River,New South Wales

A trial, monitored release on the Wingecarribee River over 27 days had a peak discharge below the Wingecarribee Dam of 1090 ML/d, which had a flow duration of 0.95 per cent. Morphological impacts on 29 km of channel below the dam included bank erosion, concentrated neck overflow, bed degradation and channel widening at recent cutoffs, sedimentation in weir pools and overbank flow, particularly at discharges greater than 800 ML/d. Prolonged operational releases at bankfull discharge (400–800 ML/d) will have the greatest morphologic impacts and should be avoided. Pulses which dissipate stream power over a broad, well-vegetated floodplain should be incorporated in the operational release policy, provided such pulses are phased to facilitate channel and vegetation recovery.     

Interpreting urban space through cognitive map sketching and sequence analysis

Traditionally, analysis of sketch maps of urban areas has focused on the interpretation of hand‐drawn renditions of features that are most familiar to individuals. Few researchers have investigated the sequence that sketchers use to identify features on the urban landscape and how these features are linked together to form a coherent ‘picture’ of an area. This article builds upon previous research by exploring the sequential pattern of sketch map creation. Two research questions are proposed, namely, can a repetitive sequential order in element inclusion be identified for different individuals sketching the same urban environment? If so what features are mapped in which order to create the sketchers' image of the city? Findings suggest that three distinct groups of cognitive maps exist, namely, sequential, spatial and hybrid, and that the map elements of each group are organised in a distinctive manner with paths and landmarks as principal elements. It is suggested that insights into this process provide more substance to understanding how individuals interpret and structure urban space and use this information to navigate both known and new environments.     

THE EFFECT OF THE REGIONAL WIND ON AIR POLLUTION IN HAMILTON, ONTARIO

Summary: By plotting low-volume aerosol counts as indices of pollution in Hamilton a pattern of dual pollution cells of equal intensity centring on the downtown business area and the heavy industrial zone emerges. Pollution levels are twice as great under east winds with accompanying atmospheric stability than for winds from all other sectors. With winds from the easterly sector the industrial pollutants are forced and locked into the lower city. When a major source of industrial pollution disappears, as happened during the 1969 shutdown of the Steel Company of Canada plant, the industrial cell vanishes and the pollution count under east winds drops to a level normal for other wind directions. With a wind change from the east to the west new pollution patterns are formed within six hours. The average pollution count for the city drops substantially but in the east end it increases as the pollution haze formerly trapped in the city is released and carried eastward.     

PROCESSUS D'EDIFICATION DE LA STRUCTURE DE POUSSÉE DU GLACIER THOMPSON, ÎLE AXEL HEIBERG, TERRITOIRES DU NORD-OUEST

Les photographies aériennes du complexe glaciaire formé par les glaciers White et Thompson (ǐle Axel Heiberg, Territoires du Nord-Ouest) acquises au cours des 30 dernières années indiquent que la structure de poussée qui se forme au front du glacier Thompson s'est élargie dans sa zone centrale ainsi que dans sa portion ouest, mais qu'elle a été comprimée dans sa portion est. Les observations sur le terrain confirment le caractère contemporain du développement asymétrique de la structure vers le sud-ouest, caractere qui a été propose dans une étude antérieure. Les observations effectuées en 1989 et en 1990 permettent ?affirmer que la structure ?empilement de blocs de graviers fluvioglaciaires qui forme ce que ?aucuns appellent la « moraine de poussée » du glacier Thompson ne résulte pas principalement de poussées horizontals de surface ni ?un dépǒt de strates de glace basale riche en materiel au front du glacier par écoulement compressif, mais plutǒt ?un ensemble de processus de nature glaciotectonique. On propose enfin un modèle de développement de la structure après avoir passé en revue les fondements théoriques de ?édification des structures de poussée en milieu gla-ciaire. The aerial photograph record depicting the proglacial area of the White and Thompson glaciers, Axel Heiberg Island, Northwest Territories, shows that the width of the Thompson Glacier push structure has increased in its western and central sectors, but has decreased in its easternmost sector over the last 30 years. The push structure, which is often referred to as a ‘push moraine’, is mainly composed of stacked up slabs of outwash material resulting from glaciotectonic activity. Recent observations were found to reinforce the asymmetric development trend of the structure toward the southwest that had been noted in an earlier study. Field observations in 1989 and 1990 also suggest that a set of processes related to glaciotectonism, rather than simple bulldozing or deposition of material-laden slabs of basal ice at the front, is mainly responsible for changes in the Thompson Glacier push structure. Theoretical aspects are discussed and a model relating to formative processes in the Thompson Glacier push structure is proposed.     

DAMMING JAMES BAY: II. IMPACTS ON COASTAL MARSHES

The damming of James Bay as proposed by the grand Canal Scheme will influence the hydrology of the coastal marshes. The salinity regime of two James Bay marshes were compared to understand the processes that govern salinity in the zone near mean high water (mhw) and to predict changes that may result from this proposed impoundment. Data suggest that sites along southern James Bay would be minimally affected because of the current low level of salinity. The northern marshes would, however, experience significant changes, as their primary source of salt is from saline tidewater. A simulation of the vertical salt and water fluxes at a northern location predicts a rapid reduction in the chloride concentration at mhw, which should approach the present values for southern James Bay in about 10 years. Above mhw, the salt will be leached quickly, so that within four years the surface chloride concentration will be reduced to the level currently found in southern James Bay.     

Water,Wind, Wood,and Trees: Interactions,Spatial Variations,Temporal Dynamics,and their Potential Role in River Rehabilitation

Recent Australian research has quantified the role of large wood (wood of any origin and length with a diameter greater than 0.1 m) in dissipating stream energy, forming pool habitats by local bed scour, protecting river banks from erosion, and damming rivers with long rafts causing avulsions. Large wood in Australian streams is sourced by a range of processes from the nearby riparian zone which has usually been degraded by post‐European settlement vegetation clearing. Large wood loadings within the bankfull channel are dependent not only on the type and quality of the riparian plant community but also on bankfull specific stream power, channel width, and the processes of large wood delivery to the stream. While bank erosion and floodplain stripping by catastrophic floods are obvious and important delivery mechanisms, treefall and trunk and branch breakage by strong winds during tropical cyclones and severe storms are also significant in the tropics. Furthermore, wood decay and downstream transport produce temporally dynamic large wood distributions. The longevity of natural large wood structures in rivers, such as rafts, debris dams, and log steps, requires determination. River rehabilitation programs need to not only include the reintroduction of large wood, but also carefully plan the spatial distribution of that wood, the most appropriate type and range of large wood structures, and, most importantly, the revegetation of the riparian zone to ensure a natural long‐term source of large wood. Exotic species management is an essential part of river rehabilitation.