Soil/Landform Unit 161

The Twelve Apostles and undulating coastal plains of the south-west coast

Area:

11 107 ha

0.83% of CMA region

Undulating plains in the south-west of the Corangamite catchment are formed on Miocene limestone, marl and calcareous clay. The landscape is quite extensive, stretching along the coastline from Princetown to Peterborough. Some faulting has led to occasional steep scarps, but most slopes are gentle and straight, separated by broad drainage lines. The gradational soils on these calcareous sediments are heavier textured and significantly more fertile than soils formed on Neogene sediments in adjacent units. Free lime is often present at depth in the soil profile. Remnants of the native vegetation indicate that it was somewhat stunted, possibly as a result of the proximity to the coast. Remnant vegetation includes stringybarks, peppermints and heathy vegetation as part of the vegetation classes Coastal Headland Scrub, Damp Heath Scrub, Shrubby Foothill Forest and Herb-rich Foothill Forest. Dairy farming is the main land use, although some of the earlier established areas close to the coast are used for sheep and beef cattle grazing. Subsoils are dispersible and gully erosion has occurred along some drainage lines. Landslip and slumping of road batters cause problems with road construction and access on the more undulating areas. Drainage lines remain waterlogged for most of the year and are prone to soil compaction by stock.

Long straight slopes with broad drainage lines typify this
	Undulating plains west of Port Campbell

Component	1	2	3	4	5
Proportion of soil-landform unit	4%	65%	20%	8%	3%
CLIMATE Rainfall (mm)	Annual: 900-1000, lowest January (40), highest August (120)
Temperature (^oC)	Annual: 14, lowest July (9), highest February (18)
Seasonal growth limitations	Temperature: less than 10^oC (av.) June-August Precipitation: less than potential evapotranspiration November-March
GEOLOGY Age and lithology	Miocene marine clay, marl and limestone in the lower reaches of the Gellibrand River catchment
Geomorphology	6.2.2 Dissected plains, rises and low hills of the Sedimentary Western Plains
LANDUSE	Cleared areas: Grazing beef cattle; dairy cattle; sheep Minor uncleared area: Nature conservation; including the rugged coastline of the Port Campbell National Park
TOPOGRAPHY Landscape	Undulating plain with some fault scarps
Elevation range (m)	0-165
Local relief (m)	45
Drainage pattern	Dendritic
Drainage density (km/km²)	2.9
Landform	Rise			Drainage lines	Fault scarp
Landform element	Upper slope and crest	Mid slope and crest	Lower slopes	-	-
Slope and range (%)	5 (2-9)	11 (4-21)	4 (1-7)	0 (0-1)	33
Slope shape	Linear	Convex	Concave	Linear	Linear
NATIVE VEGETATION Structure	Open forest	Woodland	Woodland	Closed scrub	Woodland
Dominant species	E. obliqua, E. ovata, E. aromaphloia	E. ovata, E. radiata	E. obliqua, E. ovata	Melaleuca squarrosa, Leptospermum lanigerum	E. viminalis, Acacia melanoxylon
SOIL Parent material	Clay and sand	In situ marl, limestone	Clay and sand	Plant remnants, alluvial sand and clay	In situ marl and limestone
Description (Corangamite Soil Group)	Brown texture contrast soils, coarse structure (21)	Brown calcareous gradational soils, coarse structure (22/24)	Mottled brown, yellow and grey gradational soils (22)	Grey gradational soils (22)	Black calcareous gradational soils (22/24)
Soil type sites	OTR424, OTR735	OTR784	CLRA10	OTR733, CLRA10	-
Surface texture	Fine sandy loam	Loam	Sandy loam	Silty loam	Clay
Permeability	Very low	Low	Moderate	Low	Moderate
Depth (m)	>2	1.7	>2	>2	>2
LAND CHARACTERISTICS, POTENTIAL AND LIMITATIONS	Highly dispersible soils of low permeability are prone to gully and sheet erosion. Low inherent fertility and leaching of permeable surfaces lead to nutrient decline.	Clay subsoils on steeper slopes subject to periodic saturation are prone to landslips, slumping of road batters and gully erosion.	Dispersible subsoils are prone to gully erosion.	Dispersible subsoils of low permeable receiving runoff from surrounding hills are prone to gully erosion, waterlogging and soil compaction.	Clay soils on steep slopes subject to periodic saturation are prone to landslips an sheet erosion.

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