Soil/Landform Unit 94

Depositional terrace near Chapple Vale at the juncation of the Gellibrand and Chapple rivers

Area:

2469 ha

0.18% of CMA region

High level river terrace systems have developed along the Gellibrand River valley at Carlisle River, Gellibrand and Chapple Vale. Up to four different levels can be found, and mild dissection on the upper levels results in quite complicated landscapes. The alluvial material varies from coarse sands and gravels to silts and clays, and a variety of soils is found at different levels. Redistribution of sand over some areas has resulted in polygenetic soils with hardpan development. This further complicates the soil and vegetation pattern. Most of these terrace systems have been cleared, with dairying being the major land use. Seasonal waterlogging is common and soil

compaction

may result from cattle grazing these areas in wet conditions.

Depositional terrace of Coles Creek
	Terrace and floodplain of the Gellibrand River

Component	1	2	3	4	5	6	7
Proportion of soil-landform unit	10%	10%	10%	10%	15%	25%	20%
CLIMATE Rainfall (mm)	Annual: 1000-1150, lowest January (45), highest August (130)
Temperature (^oC)	Annual: 13, lowest July (8), highest February (8)
Seasonal growth limitations	Temperature: less than 10^oC (av.) June-September Precipitation: less than potential evapotranspirational mid November-late March
GEOLOGY Age and lithology	Recent alluvial clay, silt and sand shallowly overlyign unconsolidated Paleogene sand with some clay and silt
Geomorphology	3.3.3 Alluvial terraces and floodplains associated with Dissected low hills of the Southern Uplands
LANDUSE	Cleared areas: Dairy farming; beef cattle grazing; open-range pig fattening; residential; water supply Uncleared areas: Sand and gravel extraction; water supply; minor forest produce
TOPOGRAPHY Landscape	Elevated and, in parts, uplifted and dissected system of ancient cut and depositional terraces of the Gellibrand River
Elevation range (m)	30-180
Local relief (m)	20
Drainage pattern	Dendritic pattern in dissected areas; internal drainage elsewhere
Drainage density (km/km²)	2.2
Landform	Alluvial terraces	Scarps	Valley floors	Scarps	Mildly dissected alluvial terraces
Landform element	Low level	-	-	-	Mid level	-	High level
Slope and range (%)	3 (0-8)	25 (15-40)	0 (0-1)	15 (3-35)	5 (0-9)	3 (0-5)	7 (1-10)
Slope shape	Linear	Linear	Linear	Convex	Linear	Linear	Convex
NATIVE VEGETATION Structure	Open forest	Open forest	Tall open forest	Woodland	Low open woodland	Open forest	Open forest
Dominant species	E. obliqua, E. ovata	E. obliqua, E. viminalis	E. viminalis, E. obliqua, Acacia melanoxylon, E. ovata	E. radiata, E. nitida, E. baxteri, E. viminalis	E. nitida, E. radiata, E. baxteri	E. aromaphloia, E. radiata, E. ovata	E. obliqua, E. radiata, E. baxteri
SOIL Parent material	Alluvial clay, silt, some sand	Sand, silt and clay	Alluvial clay, silt and sand	Sand	Sand	Alluvial clay, silt wtih sand underlay	Alluvial clay, silt
Description (Corangamite Soil Group)	Yellow-brown gradational soils coarse structure (34)	Brown, grey or yellow gradational soils, weak structure (29, 17)	Grey gradational soils (34)	Grey sand soils (29, 8)	Grey sand soils with hardpans (29)	Grey sand soils, structured clay underlay (11)	Mottled brown, grey, yellow and red gradational soils (29, 17)
Soil type sites	OTR750	OTR497, OTR741	OTR733	OTR742, OTR426	OTR608, SW61	OTR737	OTR746
Surface texture	Fine sandy loam	Sandy oam	Sandy clay loam	Loamy sand	Silty loam	Sandy loam	Sandy loam
Permeability	Low	High	Low	Very high	Very low	Low	Moderate
Depth (m)	>2	>2	>2	>2	0-1	>2	>2
LAND CHARACTERISTICS, POTENTIAL AND LIMITATIONS	Low permeability and high rainfall lead to seasonally high watertables with resulting waterlogging and water compaction.	Low inherent fertility and high permeability lead to leaching of nutrients. Weakly structured surface soils on the steepest slopes are prone to sheet erosion. Saturation of clay subsoils on steep slopes lead to landslips.	Flooding and seasonal watertable development lead to waterlogging, soil compaction and siltation.	Very low inherent fertility and high permeability lead to nutrient decline. Steeper slopes with compaction soils of low water holding capacity are prone to sheet erosion.	Very low inherent fertility with leaching of permeable acidic surfaces leads to nutrient decline. Hardpans restrict drainage, leading to seasonal waterlogging.	Low inherent fertility with leaching of permeable surface horizons lead to nutrient decline. Low profile permeability and perched seasonal watertables lead to waterlogging.	Low inherent fertility and phosphorus fixation lead to nutrient decline.

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