Soil/Landform Unit 176

Undulating slopes are a mixture of residual sands overlying friable loams of limestone and marl. These sands are variable in occurrence and depth across this unit

Area:

8577 ha

0.64% of CMA region

These gently undulating plains are part of the sedimentary Western Plains. This single unit is found in the south-west of the catchment, west of the Curdies River in the Nirranda, Brucknell area and is generally formed on Neogene sandy sediments and where dissection has occurred, exposed Neogene marl and limestone. The dissection of the plains is sub-parallel, draining east into the Curdies River. The unit is characterised by hillslopes, plains and depressions with the remnant vegetation including Lowland Forest, Damp Heathland/Damp Heathy Woodland Mosaic and Herb-rich Foothill Forest. The soils are

acidic

brown texture contrast soils (

Chromosols

and

Kurosols

) on the plains and grey cracking clays (

Vertosols

) in the depressions. These moderately drained soils have low nutrient levels in the lighter topsoils due to the higher rainfall of this area. Land use is grazing, generally for dairying with some minor associated cropping. Some mass movement may occur at geological or pedalogical boundaries (sandy upper soil material over marl or limestone), with sandy material moving downslope.

The undulating plains are mainly used for grazing by dairy and cropping (horticulture and fodder)

Component	1	2	3
Proportion of soil-landform unit	20%	60%	20%
CLIMATE Rainfall (mm)	Annual: 880
Temperature (^oC)	Minimum 10, Maximum 19
Precipitation less than potential evapotranspiration	November–March
GEOLOGY Age and lithology	Neogene fluvial-marine clay, sand and gravel; minor marl, calcarenite
Geomorphology	6.2.4 Plains, rises and low hills of the Sedimentary Western Plains
LANDUSE	Uncleared areas: Hardwood forestry for sawlogs, posts and poles; softwoood plantations; water supply; nature conservation Cleared areas: Dairy farming; beef cattle and sheep grazing; cropping (horticulture); softwood plantations
TOPOGRAPHY Landscape	Gently undulating plains
Elevation range (m)	6–128
Local relief (m)	10
Drainage pattern	Dendritic
Drainage density (km/km²)	1.1
Landform	Gently undulating plains		Drainage depressions
Landform element	Dissected hillslopes	Gently undulating plains	Fine drainage pattern/pediment rivulets
Slope and range (%)	3 (1–7)	1 (0–3)	1 (0–2)
Slope shape	Convex	Straight	Concave
NATIVE VEGETATION Ecological Vegetation Class	Lowland Forest (2.6%), Damp Heathland/Damp Heathy Woodland Mosaic (1.5%), Herb-rich Foothill Forest (0.9%)
SOIL Parent material	Clay, silt sand and marl	Clay, silt and sand	Clay, silt sand and marl
Description (Corangamite Soil Group)	Mottled brown, grey and yellow texture contrast soils (13)	Mottled brown, grey and yellow texture contrast soils (13)	Alkaline grey cracking clays (31)
Soil type sites	SW67, CLRA3, OTR601	SW67, CLRA3, OTR601	CLRA15, SW37, CLRA48
Surface texture	Fine sandy loam	Fine sandy loam	Medium clay
Permeability	Moderate	Moderate to low	Very low
Depth (m)	<2	<2	>2
LAND CHARACTERISTICS, POTENTIAL AND LIMITATIONS	Texture contrast, mottled with swelling clay subsoils, but light topsoils. Moderate to poor permeability, good site drainage. Low nutrient holding capacity in subsurface soil, higher in surface soil (organic matter) and subsoil (clay, some calcareous material).	Texture contrast, mottled with swelling clay subsoils, but light topsoils. Moderate to poor permeability and site drainage. Low nutrient holding capacity in subsurface soil, higher in surface soil (organic matter) and subsoil (clay).	Swelling clay soil may be strongly structured. Very poor site drainage, susceptible to waterlogging and compaction. High nutrient holding capacity, generally sodic.

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