Soil/Landform Unit 155

View north of the entrenched valley and valley floors near Shelford

Area:

7321 ha

0.55% of CMA region

Dissection of the lava plains in the Western Plains of the Corangamite region has lead to development of a steeply dissected entrenched valley with a broad

alluvial

floor. This unique landscape includes the ox-bows of the Leigh River and the Barwon River north of Winchelsea. The entrenched valley and valley floor includes Floodplain Riparian Woodland and Streambank Shrubland as the major vegetation classes. The unit has a wide variety of geologies including

Ordovician

sediments; Neogene marl, limestone, sands and gravels; Quaternary volcanics and

alluvium

. This dissection has produced steeply dissected terrain highlighting a wide diversity of geologies in these steep slopes and scarps. The unit consists of black cracking clays on the alluvial plains and in the ox-bows. Active channel aggradation or over-bank stream flow has lead to the development of deep, very poorly structured silty loams. There are minor occurrences of

mottled

brown texture contrast soils on the alluvial plains particularly in the Inverleigh area. Land use includes water supply, grazing, cropping, horticulture and residential development near Winchelsea. Erosion hazards are high at scarps and steep slopes, which have a high susceptibility to soil loss. Landslips and rock fall are also hazards of this steep terrain. Areas with shallow stony gradational soils are susceptible to

leaching

of nutrients, and

compaction

is a problem on the alluvial plains.

Valley floor with billabongs south of Shelford
	Valley flor and steep valley side slopes

Component	1	2	3	4	5	6	7	8
Proportion of soil-landform unit	7%	10%	22%	6%	25%	20%	3%	7%
CLIMATE Rainfall (mm)	Annual: 570
Temperature (^oC)	Minimum 9, Maximum 19
Precipitation less than potential evapotranspiration	October-April
GEOLOGY Age and lithology	Quaternary basalt	Neogene unconsolidated sediements - gravel, sand and clay	Various Neogene strata, unconsolidated sediments, limetstone, etc.	Ordovician slates and sandstone interbedded	Quaternary alluvium
Geomorphology	6.1.5 Alluvium, terraces, floodplains, lakes, swamps and lunettes of the Volcanic Western Plains
LANDUSE	Uncleared: Nature conservation; water supply Cleared: Sheep and beef cattle grazing; water supply; cropping; horiticulture
TOPOGRAPHY Landscape	Entrenched valley slopes and floors
Elevation range (m)	27-192
Local relief (m)	45
Drainage pattern	Dendritic
Drainage density (km/km²)	4.7
Landform	Steep river valley sides				Terrace 2	Terrace 1	Depressions and billabongs in Terrace 1	River channel bed, banks and levees
Landform element	Stony upper slope	Upper slope or crest	Mid slope	Lower slope	Higher terraces	Lower terraces	Low-lying wet areas
Slope and range (%)	32 (20-60)	20 (10-50)	20 (10-50)	20 (10-50)	2 (0-3)	1 (0-2)	0 (0-2)	1 (0-2)
Slope shape	Convex to straight	Convex	Straight to concave	Straight to concave	Straight	Straight	Concave	Concave
NATIVE VEGETATION Ecological Vegetation Class	Floodplain Riparian Woodland (3%), Streambank Shrubland (2.4%)
Dominant species		E. leucoxylon, E. camaldulensis	E. leucoxylon, E. camaldulensis	E. leucoxylon, E. melliodora, E. viminalis	E. leucoxylong, E. camaldulensis	E. camaldulensis	E. camaldulensis	E. camaldulensis
SOIL Parent material	In situ weathered basalt	In situ unconsolidated sediments with some areas of colluvial basalt	In situ unconsolidated sediments and limestone, with colluvium from higher land. some quartzite outcrops.	In situ slates and sandstone with colluvium.	Unconsolidated gravel, sand, silt and clay	Unconsolidated gravel, sand, silt and clay	Unconsolidated gravel, sand, silt and clay	Unconsolidated gravel, sand, silt and clay
Description (Corangamite Soil Group)	Stony shallow brown clay soils (39)	Black clays (31) or brown, grey or yellow texture contrast soils (39)	Black clays (39) with some red gradational or texture contrast soils (14) and some sandy creas (quartzite) (16)	Mottled brown, grey or yellow gradational or texture contrast soils (26)	Red texture contrast soils, some dark texture contrast soils (33)	Dark loams (34)	Dark clay soils (31)	Channel - variable levell - uniform fine sands (34)
Soil type sites	SFS2, SW101, SW89	SW67, CLRA3, OTR601	SW99, SW89, SW61	BD13, BD11, MM204	SW2, SW67, SW38	CLRA1, SW39, CLRA15	SW37, CLRA48, CLRA15	CLRA1, SW39, CLRA15
Surface texture	Clay loam	Clay to clay loam	Mostly clay with some sandy areas	Fine sandy clay oam	Loamy sand and sandy loam	Loam to clay loam	Clay loam to clay	Variable
Permeability	Moderate	Moderate to low	Moderate	Moderate to low	Moderate	High	Low	Moderate
Depth (m)	0.1-0.5	0.5-1.2	0.3-2.0	0.3-1.0	0.5-1.0	0.2-0.8	0.8-1.5	>2
LAND CHARACTERISTICS, POTENTIAL AND LIMITATIONS	Steep slopes are subject to undercutting, slumping and falling rocks.	Deep black clayey soils on moderate to steep slopes are subject to overland flow, moderate slip hazard and rilling on exposed soil.	Deep black clayey soils on moderate to steep slopes are subject to overland flow, moderate slip hazard and rilling on exposed soil.	Dispersible clay soils on moderate to very steep slopes are subject to overland flows, moderate sheet and rill erosion.	Overland flow and minor sheet erosion are features on exposed soils of the higher terraces.	Low situation affected by flooding and siltation from river, overland flow and periodic waterlogging.	Low situation affected by flodding and siltation from river, overland flow and periodic waterlogging.	Low situation affected by flooding and siltration from river, overland flow, periodic waterlogging and streambank erosion.

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