Accounting - Theses
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ItemTrajectories of stream evolution in response to catchment urbanisation: Cardinia Creek case study( 2022)Catchment urbanisation, via the increase of impervious surfaces and efficient drainage, triggers changes in stream channel morphology and function, commonly through channel enlargement and simplification. Disturbed streams pose significant environmental, social and economic impacts in cities and suburban areas, threatening riparian habitat, urban infrastructure and the removal of large areas of arable land. Although this enlargement trajectory is well-known, it is also highly dependent on local context factors, such as geology, topography, vegetation cover, sediment concentrations and legacies of past management. Consequently, understanding the complex relationship between hydrological drivers and local context factors in channel type formation is crucial. Taking Cardinia Creek as a case study within the urban growth belt of the Greater Melbourne Area, this research seeks to study the creek’s geomorphological evolution to analyse its response and sensitivity to urbanisation. Metrics of channel form, such as bankfull width, depth, slope, and cross-sectional shape, were quantified remotely through the use of LiDAR 2017 images and subsequently surveyed in the field following the rural-to-urban gradient of the creek. Similarly, urbanisation and local context predictor variables, including attenuated imperviousness, hardpoints, riparian vegetation cover, sediment stores, and valley confinement, were assessed to understand to what extent they could explain channel responses. Results were then analysed at the reach, site and cross-sectional level to develop a channel evolution model that describes the geomorphologic adjustments of the creek to urban perturbations. Main findings show that the central urbanised reach of the waterway has a deeper, wider and simplified channel in comparison to the upstream and downstream reaches. Additionally, a high variability of responses was found within and amongst less urbanised sites, suggesting local disturbances and context factors play an important role in local channel type formation. Thus, the channel evolution response to urbanisation does not entirely follow the fundamental sequence of enlargement by incision and subsequent widening, as the creek seems to be widening with limited incision. This finding highlights the importance of understanding local-scale context factors and legacies of past management to guide future stream management or restoration efforts.