Resource Management and Geography - Theses
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ItemThe interaction between the environment land use and hydrology of the Bogong High Plains area from 1850 to 1985( 1990)The Bogong High Plains form part of the' Australian alpine area which contributes significantly to the water resources of south-eastern Australia. The dual factors of a high average annual runoff and low levels of variability by Australian standards point to the value of the area for water production and the need for optimum management criteria. However, the hydrological response of the streams draining the alpine area to changing environmental and land use factors has not been previously addressed. In this thesis the environmental and land use history of the Bogong High Plains Area has been documented. On the basis of historical reports and photographs, management decisions affecting the Alps, and ecological studies in the Area since the 1940s, trends in the environmental condition of the Bogong High Plains Area between 1850 and 1985 have been ascertained. The land use history of the Area has been documented, including: the Aboriginal visits to the area to exploit the Bogong moth; the use of the subalpine and alpine environments by graziers and their stock: the impact of gold milling activities in the nineteenth and twentieth centuries; the frequency, cause and extent of fire in the region; the construction and management of the Kiewa Hydro-Electric Scheme; the operation of logging activities in the area; and the tourist use of the region for summer and winter recreation. An examination of the hydrological characteristics of the Bogong High Plains Area then followed. Twelve catchments were selected for analysis, ranging in size from 1.35 to 146 square kilometres, and in altitude from 634 to 1922 metres. Differences in the physical, geological, geomorphological and vegetation characteristics were related to the average annual water balances and hydrological variability. A review of the literature on the effects of fire, forestry, mining, tracks and roads, engineering works and grazing on runoff was made preparatory to an assessment of the effect of land use practices on the runoff characteristics of the twelve catchments. Standard hydrological techniques were used to assess the impact on streamflow of bushfire, insect attack, forestry operations, mining activity, road construction, construction works for the hydro scheme, and cattle grazing. Some of the results were unexpected. Although grazing was the land use of longest duration, the long-term trends in streamflow and inter-catchment comparisons based on differential grazing pressures only partially demonstrated grazing had a noticeable impact on runoff characteristics. The effect of fire, forestry, insect attack and mining activity also yielded indeterminate results. By contrast, the construction of roads and the development of the Kiewa Hydro-Electric Scheme resulted in statistically significant changes in streamflow characteristics, including runoff volumes, baseflow properties, and the magnitude of flood events. A model of the environmental history of the Bogong High Plains Area is proposed, incorporating trends in climate, fire frequency, vegetation cover, land use activity, and hydrological characteristics. From the model it is suggested that the occupation of the Bogong High Plains Area by Europeans since the 1850s has resulted in irreversible changes to the hydrological regime which predated the period of stream gauge operation and which could only be partially correlated with ecological trends. The model is used to ascertain the hydrological response of catchments to different combinations and intensities of grazing, fire and site disturbance, in association with present and alternative climatologically conditions.
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ItemRiver channel changes in Gippsland, Victoria( 1990)Channel changes during the period of European settlement on three streams in Gippsland, Victoria, the Thomson and Avon Rivers and Freestone Creek, were investigated on the basis of information contained in historical documentary sources including early maps and aerial photographs and the files and records of a number of Victorian government departments. Changes in channel position, planform characteristics, cross section, long profile and channel behaviour were analysed both qualitatively and quantitatively, revealing that river metamorphosis had occurred on parts of all three streams in the study area at different times during the period of European settlement. River metamorphosis in all cases involved changes in both channel morphology and channel behaviour; and on the Thomson River and Freestone Creek coincided with channel avulsion. A causal link between changes in the channel/floodplain relationship resulting from incision and river metamorphosis was identified. Incision associated with river metamorphosis was the result of both intrinsic geomorphological factors and human interference, the relative importance of which varied between streams. Changes in catchment-generated discharge regimes and sediment loads of sufficient magnitude to have caused river metamorphosis are considered unlikely except at the downstream end of the Avon River. Channel changes took place here in response to an increase in sediment load resulting from upstream channel changes and occurred in the absence of any major change in the channel/floodplain relationship. Since the explanation of the causes of river metamorphosis in terms of changes in the channel/floodplain relationship offered in this thesis cannot be accommodated by Schumm's (1969) widely accepted model, an alternative model of river metamorphosis is proposed. This model envisages channel morphology and behaviour as being controlled by an intrinsic sequence of channel and floodplain development, of which river metamorphosis is an inherent component. Extrinsic disturbances can cause river the intrinsic sequence and metamorphosis also even by short circuiting without this shortcircuiting. The occurrence of river metamorphosis in response to intrinsic controls and in the absence of changes in external inputs has serious implications for fluvial palaeohydrology. It means that climatic or other environmental changes cannot be validly inferred from alluvial evidence without independent supporting data.