Landslide mapping and processes in the Grampians, Victoria.
A paper by James Cameron, Honours student in Geology at Federation University Australia (formerly University of Ballarat). James recently completed research entitled Landslide mapping and processes in the Grampians, Victoria. His research thesis was submitted for examination in October 2013.
Uncharacteristically high rainfall in January 2011 caused extensive landslides in the Grampians Ranges, particularly on the east facing slopes of the Serra-Wonderland-Mt Difficult ranges. The landslides affected mostly National Park as well as private property and municipal infrastructure costing the region financially, environmentally and economically.
To mitigate future landslide hazards and risks the landslides have been mapped to determine the nature and extent (spatial and temporal), the contributing factors and the processes related to the landscape features. Using GIS 176 landslides and 274 failure points were mapped.
The failure points were noted to occur at a mean azimuth of 113.2 on slopes averaging 34.3˚ gradient. Four geological formations (Silverband Formation, Serra Sandstone-Sandstone, Wartook Sandstone and Major Mitchell Sandstone) comprised 70% of the total failures due to an average rainfall of 227.6mm. Five representative landslides were examined to have common morphological characteristics, recorded as zones: zone A (failure and erosion); zone B (erosion and transport); zone C (transport and minor deposition); zone D (minimal transport and significant deposition); zone E (remaining deposition and run-out). The landslides often had total lengths tens of times that of their width and hundreds of times the depth.
The underlying landscape and surficial environment are major controls on the spatial distribution of the landslides. These conditions are compounded by an influx of water, both surficial and sub-terrigenous, from significant rainfall to the point of failure.
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