Soil/Landform Unit 138

Lower broad depressions with minor development of a drainage line is common across this landscape

Area:

1134 ha

0.08% of CMA region

Situated near Inverleigh are gently undulating plains with well developed regolith profiles of the Western Volcanic Plains. The terrain includes slopes, depressions and stony rises of

Quaternary

volcanic origin with steeper upper slopes and crests that provide the western margin for the Sutherland Creek valley. Long gentle slopes graduate into broad drainage depressions of this landscape with residual stony rises randomly found. Similar to Unit

142

, these Quaternary volcanics have provided a resistant capping for underlying Palaeogene/Neogene sediments that appear more prone to weathering and degradation. Soils of these gentle slopes includes

yellow or grey

soils with black

clays found on lower slopes and depressions. Stony rises tend to have shallow stony red gradational soils. The upper slopes and crests of the Sutherland Creek tend to be a mix of clays soils of varying depth. Land clearance has been widespread with few remnant vegetation groups (Plains Grassland 0.5% and Plains Grassy Woodland 0.3%). Land use is mainly grazing. Poor management can lead to significant soil

compaction

and inadequate ground coverage is responsible for high overland flow and sheet erosion.

Cropping on gentle slopes with adequate land management can avoid soil eroson and degradation

Component	1	2	3	4	5
Proportion of soil-landform unit	78%	2%	2%	8%	10%
CLIMATE Rainfall (mm)	Annual: 550
Temperature (^oC)	Minimum 9, Maximum 19
Precipitation less than potential evapotranspiration	October-April
GEOLOGY Age and lithology	Pleistocene basalt, Neogene unconsolidated fluvial sediments - gravel, sand and clay
Geomorphology	6.1.4 Volcanic Western Plains with well developed drainage
LANDUSE	Uncleared: Nature conservation Cleared: Sheep and cattle grazing; cropping
TOPOGRAPHY Landscape	Gently undulating plains
Elevation range (m)	44-194
Local relief (m)	2
Drainage pattern	Dendritic
Drainage density (km/km²)	0.3
Landform	Depressions			Scarps	Sides of the river valley
Landform element	Long gentle upper slopes	Depression	Stony rise	Stony upper slope or crest	Upper slope or crest
Slope and range (%)	1 (1-3)	1 (1-2)	3 (2-5)	35 (20-60)	20 (10-50)
Slope shape	Straight	Straight	Convex	Convex to straight	Convex
NATIVE VEGETATION Ecological Vegetation Class	Plains Grasslands (0.5%); Plains Grassy Woodland (0.3%)
Dominant species	E. ovata, E. viminalis, E. rubida, E. obliqua	E. ovata, E. viminalis, E. rubida, E. obliqua	E. ovata, E. viminalis, E. rubida, E. obliqua	E. leucoxylon, E. camaldulensis	E. leucoxylon, E. camaldulensis
SOIL Parent material	In situ weathered basalt	Alluvium	In situ weathered basalt	In situ weathered basalt	In situ unconsolidated sediments with some areas of colluvial basalt
Description (Corangamite Soil Group)	Mottled brown, grey or yellow, grey sodic texture contrast soil, coarse structure (35/36)	Black clay soil, coarse structure (31)	Red shallow, stony gradational soil (40)	Stony shallow brown clay soils (39)	Black clays (39) or brown, grey or yellow texture contrast soils (35)
Soil type sites	SFS6, MM5015, SW90	CLRA48, SW37, CLRA35	BD5, SW96, SW26	SW102, SW101, SW103	SW102, SW101, SW90
Surface texture	Clay loam	Clay	Clay loam	Clay loam	Clay to clay loam
Permeability	Moderate-low	Moderate	High	Moderate	Moderate-low
Depth (m)	1.5	1.5	0.5	0.1-0.5	0.5-1.2
LAND CHARACTERISTICS, POTENTIAL AND LIMITATIONS	Soils tend to have hardsetting surfaces with slowly permeable subsoils. As a result overland flow is common. Periodic waterlogging is seasonal. Surface compaction can be alleviated by addition of organic matter.	Clay soils beside creeks are prone to waterlogging. Streambank undercutting occurs with major rainfall events, however can benefit from adequate vegetation coverage and stock protection.	Overland flow prominent due to shallow soil depth. Leaching of nutrients (nutrient decline) also a limitation of these rises along with sheet erosion. Compaction of surfaces can benefit from addition of organic matter.	The steep slopes have undercutting, slumping and rock fall.	Moderate to steep slopes of the river valley have productive deep black clayey soils. Slumping and rock fall can occur on steepest slopes. A moderate slip hazard occurs on exposed slopes and rilling on exposed soil can be an issue.

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