Simpson Land System

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Small remnants of flat lateritic plateaux near Simpson and extending towards Irrewillipe are evidence of former widespread lateritization. Most lateritic hill capping have been removed by dissection, and this set of north-nor’-west- and south-sou’-east-orientated ridges is the only significant remnant to the west of the Range.

The most common soils have gradational profiles containing lateritic ironstone. However, some profiles possess sand veneers in the surface horizons, with hardpans overlying mottled clays. Drainage of the landscape is poor, particularly where hardpans occur, and seasonal waterlogging is a problem.

The ridges have been extensively cleared as part of the Heytesbury Settlement Scheme and dairy farming is the main land use. There are problems arising from low soil fertility and exposure to wind. Only one small area of native vegetation remains in the study area.

A Study of land in the catchments of the Otway Range and adjacent plains - simpson

Clearing of these flat lateritic plateau has been very thorough,
and little evidence remains of the former hardwood forests that covered them.

Area: 33 km²	Component and its proportion of land system
Area: 33 km²	1 65%	2 25%	3 10%
CLIMATE Rainfall, mm	Annual: 800 – 950, lowest January (35), highest August (110)
Temperature, 0^oC	Annual: 13, lowest July (8), highest February (18)
	Temperature: less than 10^oC (av.) June – August
	Precipitation: less than potential evapotranspiration late October – early April
GEOLOGY Age, lithology		Pliocene lateritized sand and clay Veneer of Quaternary sand
TOPOGRAPHY Landscape	Very gently undulating plateau with north-west and south-east dissection
Elevation, m	150 – 170
Local relief, m	10
Drainage pattern	Parallel
Drainage density, km/km²	1.0
Land form	Plateau
Land form element	Middle and upper slopes, crest	Middle slope	Lower slope, depression
Slope (and range), %	4 (0-14)	0 (0-3)	5 (0-9)
Slope shape	Straight (some convex)	Straight	Concave
NATIVE VEGETATION Structure	Open forest	Closed scrub	Open forest
Dominant species	E. obliqua, E. baxteri	Leptospermum juniperinum Melaleuca squarrosa, E. nitida, Casuarina littoralis	E. baxteri, E. ovata
SOIL Parent material	Weathering lateritic remnants	Lateritic remnants covered by varying depths of sand	Alluvial sand and clay
Description	Mottled yellow and red gradational soils with ironstone	Grey sand soils, structured clay underlay	Yellow-brown gradational soils, coarse structure
Surface texture	Sandy loam	Sandy loam	Sandy loam
Permeability	Moderate	Low	Low
Depth, m	1.7	>2	>2
LAND USE	Cleared areas: Dairy farming; some beef cattle grazing Minor cleared areas: Hardwood forestry production
SOIL DETERIORATION HAZARD Critical land features, processes, forms	Low inherent fertility and phosphorus fixation lead to nutrient decline. Leaching of salts lead to increased salinity to drainage waters.	Low inherent fertility and leaching of permeable surface horizons lead to nutrient decline. Low permeabilities lead to seasonal waterlogging and soil compaction.	Low permeabilities and high seasonal watertables lead to seasonal waterlogging and soil compaction. Leaching of salts from landscape leads to increased salinity of drainage waters.