Soil/Landform Unit 170

Looking west towards the Heytesbury. The undulating rises of this unit occur at the footslopes of the Otway Ranges.

Area:

5437 ha

0.41% of CMA region

Sedimentary undulating rises near Larpent (south-west of Colac), are characterised by crests, slopes and drained plains that adjoin the steeply dissected areas of the Heytesbury region. This single southern unit located within the Western Plains has formed on Neogene sandy sediments and is bound by rolling hills (Unit

) to the south and alluvial flats (Unit

191

) to the north. This unit is part of a foothill complex to the Southern Uplands. The soils are brown mottled texture contrast soils (Chromosols) with minor mottled black texture contrast soils (Chromosols); and the remnant vegetation class is Lowland Forest. Rainfall increases to the south and supports grazing as well as some softwood and hardwood timber plantations. The light topsoils are susceptible to nutrient decline, and steeper slopes are susceptible to sheet and rill erosion.

Cleared undulating rises near Irrewillipe are mainly used for dairy farming
	Sandy brown mottled texture contrast soils are indicative of soils across these plains

Component	1	2	3
Proportion of soil-landform unit	20%	60%	20%
CLIMATE Rainfall (mm)	Annual: 900
Temperature (^oC)	Minimum 8, Maximum 18
Precipitation less than potential evapotranspiration	November - March
GEOLOGY Age and lithology	Paleogene marine carbonaceous clay, silt and sand and Neogene fluvial-marine clay sand and gravel
Geomorphology	6.2.4 Plains, ries and low hills of the Sedimentary Western Plains
LANDUSE	Uncleared areas: Nature conservation; water supply Cleared areas: Dairy farming; beef cattle and sheep grazing; softwood plantations
TOPOGRAPHY Landscape	Undulating rises
Elevation range (m)	134-209
Local relief (m)	25
Drainage pattern	Centripetal-parallel
Drainage density (km/km²)	0.7
Landform	Rises		Plains
Landform element	Crests and upper slopes	Mid and lower slopes	Plains and drainage lines
Slope and range (%)	5 (1-10)	6 (3-10)	1 (0-2)
Slope shape	Convex	Convex	Straight
NATIVE VEGETATION Ecological Vegetation Class	Lowland Forest (2.4%)
SOIL Parent material	Clay, sand and gravel and carbonaceous clay, silt and sand	Clay, sand and gravel and carbonaceous clay, silt and sand	Clay, sand and gravel and carbonaceous clay, silt and sand
Description (Corangamite Soil Group)	Neutral and acidic brown mottled texture contrast soils (13)	Neutral and acidic brown mottled texture contrast soils (13)	Neutral and acidic brown mottled texture contrast soils (13) and black, grey and yellow texture contrast soils (20)
Soil type sites	SW66, SW68, SW67	SW67, SW69, MM363	SW67, OTR601, SW77
Surface texture	Fine sandy loam	Fine sandy loam, light fine sandy clay loam	Fine sandy loam
Permeability	Moderate	Moderate to low	Very low
Depth (m)	<2	<2	>2
LAND CHARACTERISTICS, POTENTIAL AND LIMITATIONS	Strong texture contrast, low water holding capacity and nutrient holding capacity in surface soils, higher in subsoil. Low to moderate permeability in subsoil. Leaching more likely in subsurface and surface soil. Moderate rapid site drainage.	Strong texture contrast, low water holding capacity and nutrient holding capacity in surface soils, higher in subsoil. Low permeability in subsoil. Leaching more likely in subsurface and surface soil. Moderately rapid to slow site drainage.	Strong texture contrast, low water holding capacity and nutrient holding capacity in surface soils, higher in subsoil. Low permeability in subsoil. Leaching more likely in subsurface and surface soil. Slow site drainage.

Page top