Birregurra Land System

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Lying between the basalt plains to the north and dissected lateritized landscapes to the south, much, if not all, of this flat plain apparently marks the eastern extent of a large former lake in western Victoria. The landscape slopes very gently to the east with increasing dissection as the height above the Barwon River flood plain increases from 10 m to about 40 m.

The lacustrine deposits appear to be mainly calcareous and have formed soils with alkaline reaction trends. Dissolution of calcium carbonate has led to the development of sink holes in some areas, although levelling of paddocks has made these less apparent.

The native vegetation has been almost completely removed for agricultural use and its original structure and composition are difficult to determine. In the east there is some evidence of a former woodland, but further west the soils are less well drained and possibly the communities were more stunted.

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

The western parts of the land system show very little dissection
and form a flat plain between the Tertiary sediments in the south
and the basalt in the north.

Area: 81 km²	Component and its proportion of land system
Area: 81 km²	1 80%	2 10%	3 10%
CLIMATE Rainfall, mm	Annual: 600 – 650, lowest January (30), highest February (75)
Temperature, 0^oC	Annual: 13, lowest July (8), highest February (19)
	Temperature: less than 10^oC (av.) June - August
	Precipitation: less than potential evapotranspiration October – late April
GEOLOGY Age, lithology	Pleistocene clay, silt and some sand
TOPOGRAPHY Landscape	Flat plain bordering the present flood plain of the Barwon River
Elevation, m	110 – 130
Local relief, m	10
Drainage pattern	Dendritic
Drainage density, km/km²	0.8
Land form	Flat plain
Land form element	Flat plain	Sinkhole	Younger terrace
Slope (and range), %	1 (0-3)	0 (0-1)	2 (1-3)
Slope shape	Linear	Concave	Linear
NATIVE VEGETATION Structure	Woodland	Sedgeland	Woodland
Dominant species	E. viminalis, E. ovata	Carex spp. Scirpus calocarpus, Schoenus apogon, Juncus spp. Ranunculus spp.	E. ovata, E. camaldulensis
SOIL Parent material	Calcareous clay	Sedgeland	Woodland
Description	Yellow-brown calcareous duplex soils, coarse structure	Grey calcareous sodic clay soils, uniform texture	Grey gradational soils
Surface texture	Fine sandy loam	Clay	Clay loam
Permeability	Very low	Very low	Very low
Depth, m	>2	>2	>2
LAND USE	Sheep and beef cattle grazing; dairy farming; cropping.
SOIL DETERIORATION HAZARD Critical land features, processes, forms	Dispersible clay subsoils of low permeability and prone to gully and tunnel erosion. Seasonally high water tables lead to soil salting.	High water tables and low permeability lead to waterlogging, soil compaction and soil salting.	High seasonal water table, low permeability and saline groundwater lead to waterlogging, soil compactions and soil salting.

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