Soil/Landform Unit 195

Plains, swamps, rivers and lakes of the Moolap Sunklands

Area:

2141 ha

0.16% of CMA region

This land unit lies to the east of Geelong and known as part of the Moolap Sunklands, consisting of low relief of undulating plains of colluvial and alluvial origin dropping to a recent level of flats and swamps. This unit is part of the Western Plains (

alluvial

group) with the Southern Uplands to the east. This unit is adjacent to the swamp and lake system of the Barwon River to the south and west, and the uplifted plateau of Neogene sediments to the east. The rise to the plateau is an escarpment that provides views to Geelong from townships such as Leopold. Much of the material for this unit is supposed to have come off the escarpment as colluvium. Little remnant vegetation occurs in this unit with less then <2% Plains Grassy Woodland found. Local relief is very low making this unit prone to inundation and limiting urban development to low density housing, sporting complexes and other recreational and conservation uses.

This is accentuated by the presence of heavy

sodic

soils.

Broadacre grazing and low level development occupy this low relief undulating plain, which is subject to inundation
	Saline coastal flats form the edge of this unit to the north and west

Component	1	2	3
Proportion of soil-landform unit	20%	70%	10%
CLIMATE Rainfall (mm)	Annual: 560
Temperature (^oC)	Minimum 10, Maximum 19
Precipitation less than potential evapotranspiration	October–April
GEOLOGY Age and lithology	Recent fluvial and marine clay, sand, gravel and coastal sand dunes
Geomorphology	6.2.5 Alluvium, alluvial terraces, floodplains and coastal plains of the Sedimentary Western Plains
LANDUSE	Uncleared: Nature conservation Cleared: Sheep and beef cattle grazing; cropping (cereal)
TOPOGRAPHY Landscape	Gently undulating plain
Elevation range (m)	5–20
Local relief (m)	3
Drainage pattern	Deranged
Drainage density (km/km²)	0.6
Landform	Undulating plain		Floodplain and depressions
Landform element	Gentle rises	Plain	Flat surface
Slope and range (%)	3 (1-5)	2 (1-4)	0 (0-1)
Slope shape	Convex	Straight	Straight
NATIVE VEGETATION Ecological Vegetation Class	Plains Grassy Woodland (1.7%)
SOIL Parent material	Clay, silt and sand	Clay, silt and sand	Clay, silt and sand
Description (Corangamite Soil Group)	Grey-brown texture contrast and gradational soils (32)	Brown, grey or yellow texture contrast and gradational soils (32), weak structure and grey cracking clays (31)	Grey sand/clay soils with hardpans (31)
Soil type sites	SW88, SW95, CLRA4	CLRA35, SW88, CLRA15	SW37, CLRA48, CLRA15
Surface texture	Loam, fine sandy	Loam, fine sandy, light clay	Light clay
Permeability	Low	Low to very low	Very low
Depth (m)	>2	>2	>2
LAND CHARACTERISTICS, POTENTIAL AND LIMITATIONS	Texture contrast. Sodic, often expansive clay subsoil, low permeability when wet. Imperfect site drainage. Surface soil has low to moderate water holding capacity and nutrient holding capacity but moderate permability restricted by subsoil.	Texture contrast. Sodic, often expansive clay subsoil, low permeability when wet. Poor site drainage. Surface soil has low to moderate water holding capacity and nutrient holding capacity but moderate permability restricted by subsoil.	Heavy clay soil sometimes texture contrast. Sodic, often expansive clay subsoil, low permeability when wet. Very poor site drainage. Surface moderate to high water holding capacity and nutrient holding capacity but moderate permeability in dry state becomes very low when wet due to expansive clays.

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