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Soil/Landform Unit 57

Landform Unit Description

Unit 57 image a
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.
Unit 57 geomorphology

Unit 57 image b
The vegetation differences reflect soil and water
availability differences
Unit 57 cross section

Unit 57 graph

Unit 57 image c
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
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
SW88, SW95, MM112
SW99, SW93, CLRA33
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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