Soil/Landform Unit 57

The entrenched valleys and slopes of the upper Moorabool River are prominent landforms of the dissected volcanic and sedimentary plains

Area:

26 302 ha

1.97% of CMA region

Dissection of the lava plains, sediments and granites of the Western Uplands and plains of the Corangamite region has led to the development of dissected entrenched valleys with narrow to broad alluvial floors. This unique landscape includes the Moorabool River in the east and minor streams on the basalt plains in the west. The entrenched valley and valley floor supports the vegetation classes of Grassy Dry Forest, Valley Grassy Forest, Stream-bank Shrubland, Floodplain Riparian Woodland and Plains Grassy Woodland. Importantly the vegetation differs considerably from the Moorabool River to the basalt streams of the west. The main soil type of the unit is the black cracking clays with dark brown uniform soils of the

alluvial

plains. Terraces and lower slopes support yellow and brown texture contrast soils while the steep slopes and valley sides have black clays with some red gradational or texture contrast soils and some sandy areas (soils here can be quite variable depending on the host geology). Land use is quite variable and includes water supply, grazing, cropping, horticulture and nature conservation. Erosion hazards are high on the scarps and steep slopes, which have a high susceptibility to soil loss. Landslip and rock falls are also hazards of the steeper terrain. Areas with shallow soils are susceptible to

leaching

of nutrients, and

compaction

is a problem on the alluvial plains along with waterlogging and flooding in wet seasons.

The vegetation differences reflect soil and water availability differences
	Minor streams of the basalt plains congregate in the upper catchment to eventuall drain into Lake Corangamite

Component	1	2	3	4	5	6	7
Proportion of soil-landform unit	70%	2%	2%	2%	8%	8%	8%
CLIMATE Rainfall (mm)	Annual: 620
Temperature (^oC)	Minimum 8, Maximum 19
Precipitation less than potential evapotranspiration	October-March
GEOLOGY Age and lithology	Quaternary; river deposits, gravels, sands and clays
Geomorphology	6.1.5 Alluvium, terraces, floodplains, lakes, swamp and lunettes of the Volcanic Western Plains, 6.2.5 Alluvium, alluvial terraces, floodplains and coastal plains of the Sedimentary Western Plains and 2.1.5 Alluvial terraces, floodplains and swamps of the Western Uplands
LANDUSE	Uncleared: Nature conservation; water supply Cleared: Sheep and beef cattle grazing; cropping
TOPOGRAPHY Landscape	Alluvial plain and valley sides
Elevation range (m)	5-614
Local relief (m)	5-40
Drainage pattern	Dendritic
Drainage density (km/km²)	3.4
Landform	Terraces				Valley sides
Landform element	Terraces				Stony upper slopes or crest	Mid slope	Lower slopes
Slope and range (%)	1 (1-2)	1 (1-2)	1 (1-2)	2 (1-4)	32 (20-60)	25 (10-50)	25 (10-50)
Slope shape	Straight	Straight	Straight	Straight	Convex to straight	Straight to concave	Straight to concave
NATIVE VEGETATION Ecological Vegetation Class	Grassy Dry Forest (3.6%), Valley Grassy Forest (1.9%), Stream-bank Shrubland (1.7%), Floodplain Riparian Woodland (1.3%), Plains Grassy Woodland (1.3%), and others (3.5%)
SOIL Parent material	Unconsolidated gravel, sand, silt and clay	Unconsolidated gravel, sand, silt and clay	Unconsolidated gravel, sand, silt and clay	Unconsolidated gravel, sand, silt and clay	In situ weathered basalt	In situ unconsolidated sediments and limestone, with colluvium from higher land. Some quartzite outcrops.	In situ slates and sandstone with colluvium
Description (Corangamite Soil Group)	Dark brown loam soils (variable) (34)	Yellow brown texture contrast soil (32)	Yellow brown texture contrast soil, coarse structure (32)	Brown, grey or yellow texture contrast soil (33)	Stony shallow brown clay soils (37)	Black clays (24) with some red gradational or texture contrast soils (14) and some sandy areas (quartzite)	Mottled brown, grey or yellow gradational or texture contrast soils (33)
Soil type sites	CLRA1, SW39	SW88, SFS20, MM112	SW88, SW95, MM112	SW2, SW67, SW38	SFS5b, SW48, SW25	SW99, SW93, CLRA33	SW2, SW67, SW38
Surface texture	Fine sandy clay loam	Sandy clay loam	Medium sandy clay loam	Clay loam	Clay loam	Mostly clay with some sandy rises	Fine sandy clay loam
Permeability	Moderate to low	Moderate to low	Moderate to low	Moderate to low	Moderate	Moderate	Moderate to low
Depth (m)	2	2	2	2	0.1-0.5	0.3-0.2	0.3-1.0
LAND CHARACTERISTICS, POTENTIAL AND LIMITATIONS	Low-lying areas receiving drainage are prone to waterlogging stream bank erosion.	Low permeability soils with weak surface structure. Hardsetting surfaces causes overland flow and erosion. Movement of salts occurs through subsurface flow.	Low permeability soils have weak surface structure topsoil that is hardsetting. Overland flow and subsurface flow concentrate movement of salts with waterlogging. Streambank and gully erosion occur with major flows.	Low permeability soils have weak surface structure topsoil that is hardsetting. Overland flow and subsurface flow concentrate movement of salts with waterlogging. Streambank and gully erosion occur with major flows.	Steep slopes and stream undercutting causes, slumping and rock falls.	Moderate to steep slopes with deep black clayey soils are of moderate slip hazard. Overland flows can cause rilling on exposed soil.	Moderate to steep slopes with deep black clayey soils are of moderate slip hazard. Overland flows can cause rilling on exposed soil.

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