Bunker Hill Land System

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Deeply dissected hills north and west of Gellibrand possess Tertiary sands and clays on the higher parts of the landscape and outcrops of Cretaceous sediments on the steeper and lower parts. The soils become heavier and more fertile on the Cretaceous sediments and this is reflected in the occurrence of Eucalyptus obliqua and E. viminalis open forests with dense understoreys.

Most areas are too steep for agriculture, and remain forested with native hardwoods or pines. Clearing operations necessary for pine conversion and hardwood harvesting may result in severe scour gullying and landslips on the steep parts of the landscape.

Access tracks are difficult to site and prone to scouring. In general, careful management is required.

A Study of land in the catchments of the Otway Range and adjacent plains - bunker hill

The steep land and irregular nature of the terrain makes
these areas difficult to manage.

Area: 41 km²	Component and its proportion of land system
Area: 41 km²	1 25%	2 20%	3 40%	4 9%	5 6%
CLIMATE Rainfall, mm	Annual: 900 – 1,050, lowest January (45), highest August (130)
Temperature, 0^oC	Annual: 12, lowest July (7), highest February (18)
	Temperature: less than 10^oC (av.) June – August
	Precipitation: less than potential evapotranspiration early November – late March
GEOLOGY Age, lithology	Palaeocene unconsolidated sand, silt and clay		Lower Cretaceous sandstone and mudstone	Palaeocene unconsolidated sand, silt and clay
TOPOGRAPHY Landscape	Deeply dissected hills abutting the Gellibrand River to the west of Love Creek
Elevation, m	60 – 290
Local relief, m	95
Drainage pattern	Dendritic with some radial areas
Drainage density, km/km²	3.2
Land form	Hill
Land form element	Crests, upper slope	Slope	Steep lower slope	Gentle slope	Crest, upper slope
Slope (and range), %	20 (5-35)	30 (20-35)	45 (30-65)	15 (4-20)	13 (1-20)
Slope shape	Convex	Convex	Linear	Concave	Convex
NATIVE VEGETATION Structure	Woodland	Open forest	Open forest	Low woodland	Woodland
Dominant species	E. nitida, E. radiata, E. baxteri	E. baxteri, E. obliqua	E. obliqua, E. ovata, E. viminalis, E. aromaphloia, on southern aspect E. cypellocarpa	E. nitida, E. ovata, E. baxteri	E. radiata, E. baxteri, E. nitida, E. obliqua
SOIL Parent material	Sand	Sand, silt and clay	In-site weathered rock	Sand	Quartz gravel, some clay, sand and silt
Description	Grey sand soils, uniform texture	Yellow gradational soils, weak structure	Brown gradational soils	Grey sand soils with hardpans, uniform texture	Stony yellow gradational soils
Surface texture	Loamy sand	Sandy loam	Loam	Loamy sand	Loamy sand
Permeability	Very high	High	Moderate	Very low	Very high
Depth, m	>2	>2	0.9	0.5	>2
LAND USE	Uncleared areas: Hardwood forestry for posts and poles, some sawlogs on better soils; nature conservation; water supply; gravel extraction; softwood plantations. Cleared areas: Beef cattle and sheep grazing on mainly unimproved pastures; water supply
SOIL DETERIORATION HAZARD Critical land features, processes, forms	Low inherent fertility and high permeability lead to leaching and nutrient decline. When disturbed and compacted, steeper slopes are prone to erosion (scouring).	Low inherent fertility and high permeability lead to nutrient decline. Weakly structured surface soils are prone to sheet erosion on steeper slopes.	Steeper slopes are prone to sheet and rill erosion. Clay subsoils subject to periodic saturation are prone to landslips	Low inherent fertility leads to nutrient decline. Hardpans restrict vertical drainage leading to seasonal waterlogging.	Very low inherent fertility and high permeability lead to leaching and nutrient decline.

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