Soil/Landform Unit - Horsham South flat plain

Looking north-east over the Horsham south flat plains and MacKenzie River towards Mount Zero and Green Lake

Area: 37 508 ha

1.60% of CMA region

This unit of very low relative relief terrain includes plains and sand plains north of the Grampians Ranges and western Black Range, and south of Natimuk. These flat plains are derived from

and

sediments that overlie older

Cainozoic

sediments linked to the tablelands in the south. There are four landform components including the level plain, sand plain (sandsheet), drainage lines and swamps. Drainage is dendritic and, along with swamps, is not overly incised into the landscape. Grey cracking clay soils (

Vertosols

) on plains and in local depressions occurs as well as yellow and grey

sodic

texture contrast soils (

Sodosols

). Periodic inundation and waterlogging can occur in the depressions and extensive flat areas. This unit is used for dryland cropping, grazing (sheep, beef cattle) and water supply. Remnant vegetation communities include Plains Woodland, Shallow Sands Woodland, Creekline Sedgy Woodland, Riparian Woodland, Red Gum Wetland and Plains Grassy Woodland.

Plains north-east of Telngatuk
	Roadside remnant vegetation

Component	1	2	3	4
Proportion of soil-landform unit	85%	10%	2%	3%
CLIMATE Rainfall (mm)	Annual: 555
CLIMATE Rainfall (mm)	Annual: 555
Temperature (^oC)	Minimum 8, Maximum 21
Precipitation less than potential evapotranspiration	October–April
GEOLOGY Age and lithology	Neogene marine sand and silt (Parilla Sand); Quaternary paludal silt and clay; Quaternary fluvial silt, sand and minor gravel (Shepparton Formation)
GEOLOGY Age and lithology
Geomorphology	4.3 Pediments, alluvial fans and aprons
LANDUSE	Uncleared areas: water supply; nature conservation Cleared areas: dryland cropping; sheep and beef cattle grazing; water supply
LANDUSE
TOPOGRAPHY Landscape	Flat plains
TOPOGRAPHY Landscape	Flat plains
Elevation range (m)	134–216
Local relief (m)	2
Drainage pattern	Dendritic
Drainage density (km/km²)	0.6
Landform	Plains
Landform element	Level plain	Sandsheet	Drainage line	Swamp
Slope and range (%)	1 (0-3)	2 (1-5)	1 (0-2)	0 (0-1)
Slope shape	Straight	Linear	Concave	Concave
NATIVE VEGETATION Ecological Vegetation Class	Plains Woodland (50.0%), Creekline Sedgy Woodland (20.3%), Riparian Woodland (13.3%), Other (16.4%)
NATIVE VEGETATION Ecological Vegetation Class
SOIL Parent material	Marine sand and silt	Aeolian sand, silt and clay	Alluvial gravel, sand and silt	Paludal silt and clay
SOIL Parent material	Marine sand and silt	Aeolian sand, silt and clay	Alluvial gravel, sand and silt	Paludal silt and clay
Description (Corangamite Soil Group)	Cracking clay soils (23)	Sodic yellow and grey texture contrast soils (32)	Cracking clay soils (23)	Seasonally wet soils: sodic yellow and grey texture contrast soils (33)
Soil type sites	WIA11, WIA12, WIA17, HOR04	LSWW8, LSWW7, WIA24, WIA31	WIA11, WIA12, WIA17, HOR04	NA171, NA141, NA178
Surface texture	Light clay	Loamy sand	Light clay	Sand
Permeability	Very slow	Moderate to high	Very slow	Slow to very slow
Depth (m)	> 2	> 1.5	> 2	> 1.5
LAND CHARACTERISTICS, POTENTIAL AND LIMITATIONS Critical land features, processes, forms	Flat areas susceptible to inundation and waterlogging, but can be variable locally due to micro relief (gilgai). Surface soils generally not friable and are susceptible to compaction (weakly structured).	Susceptible to wind and sheet erosion where exposed. Low inherent fertility but well drained to pans or subsoil. Susceptible to compaction where hardsetting and poor drainage occurs.	Drainage lines are susceptible to inundation and waterlogging. Surface soils generally not friable and are susceptible to compaction.	Susceptible to seasonal inundation, waterlogging and ultimately soil salinity. Surface soils susceptible to sheet erosion and wind erosion when exposed.

Page top