Soil/Landform Unit 75

Steeply dissected coastal plain with blue gum plantations near Johanna

Area:

2638 ha

0.20% of CMA region

In the vicinity of Cape Otway, outcrops of Paleogene clay, silt, sand, limestone and marl all exist. Three separate areas - Johanna, Hordern Vale, and inland from Point Franklin and Blanket Bay. All areas are generally similar, but possess distinct differences in specific features. The limestone and marl outcrops are confined to marine terraces at Hordern Vale. The Johanna area is distinguished by its dominance of red sands. The area east of Cape Otway includes hilltops of kaolinitic clay and silt and these carry rare low woodlands of

Eucalyptus kitsoniona

. In general, these landscapes are old with areas of ferruginised soils on the highest parts. Recent dissection has often been superimposed on the more undulating areas, resulting in straight slopes with youthful soil profiles. Land uses are very diverse. Areas that have been cleared are used for dairy farming, grazing of sheep and beef cattle, a small amount of potato growing and more recently blue gum plantations. Those areas that remain uncleared are selectively logged, and also have nature conservation values. Sheet erosion and landslips have been quite severe on some of the steeper areas, and some gully erosion occurs on the slopes coming away from the ferruginised areas.

Valley floor with steep lower colluvial slopes
	Floodplain of the valley floor near Johanna

Component	1	2	3	4	5	6	7
Proportion of soil-landform unit	20%	8%	7%	4%	25%	30%	6%
CLIMATE Rainfall (mm)	Annual: 900-1250, lowest January (50), highest July (130)
Temperature (^oC)	Annual: 13, lowest July (9), highest February (17)
Seasonal growth limitations	Temperature: less than 10oC (av.) July Precipitation: less than potential evapotranspiration late November-February
GEOLOGY Age and lithology	Paleogene marine carbonaceous clay to sand; Cretaceous fluvio-volcanic sediments; Neogene marine marl.
Geomorphology	3.2.2 Dissected upland ranges of the Southern Uplands
LANDUSE	Cleared areas: Beef cattle grazing; dairy frming; sheet grazing; row crops Uncleared areas: Hardwood forestry for sawlogs and pulpwood; sand extraction; nature conservation; passive recreation
TOPOGRAPHY Landscape	Undulating coastal plain surrounding Cape Otway
Elevation range (m)	0-200
Local relief (m)	60
Drainage pattern	Dendritic
Drainage density (km/km²)	2.2
Landform	Rises	Valley floors			Rises
Landform element	Upper slope and crest	Slope and river terrace	Swale	Marine terrace	Steeper slope	Upper slope and crest	Rise
Slope and range (%)	5 (1-15)	7 (1-15)	0 (0-1)	25 (10-55)	30 (3-45)	8 (2-20)	3 (0-7)
Slope shape	Convex	Linear	Concave	Convex	Linear	Linear	Irregular
NATIVE VEGETATION Structure	Open forest	Open forest	Closed scrub	Woodland	Open forest	Tall open forest	Low woodland
Dominant species	E. obliqua, E. baxteri, E. cypellocarpa, E. aromaphloia, E. viminalis	E. obliqua, E. baxteri, E. viminalis, E. ovata	Leptospermum lanigerum	E. obliqua, E. viminalis	E. obliqua, E. cypellocarpa. E. baxteri	E. cypellocarpa, E. obliqua, E. viminalis, E. globulus	E. kitsoniana, Melaleuca squarrosa, Melaleuca ericifolia
SOIL Parent material	Ferruginsed sediments	Clay, silt and sand	Alluvial clay, silt and sand	Freshely weathered limestone and marl	Quartz sand	Clay, silt and sand	Kaolinitic clay, silt and sand
Description (Corangamite Soil Group)	Mottled brown, grey, yellow and red graational soils with ironstone (29)	Yellow-brown gradational soils, coarse strcture (29)	Grey gradational soils (29)	Black cretaceous gradational soils (24)	Red sandy loam soils (29)	Brown gradational soils (29)	Pale brown gradational soils, weak structure (29)
Soil type sites	OTR782	OTR750	OTR722	CLRA32	-	OTR414, COF01, OTR736	-
Surface texture	Gravelly sand	Fine sandy loam	Sandy loam	Fine sandy clay loam	Loamy sand	Fine sandy loam	Silty loam
Permeability	Moderate	Low	Very low	Low	Very high	High	Very low
Depth (m)	>2	>2	>2	0.5	>2	>2	>2
LAND CHARACTERISTICS, POTENTIAL AND LIMITATIONS	Low inherent fertility and phosphorus fixation lead to nutrient decline.	Dispersible subsoils are prone to gully erosion.	High seasonal water table and low permeability lead to waterlogging and soil compaction.	Clay subsoils on steep slopes subject to periodic saturation are prone to landslips.	Steep slopes with weakly structured soils are prone to some sheet erosion. High rainfall and high permeability lead to nutrient decline.	High rainfall, high permeability and leaching lead to nutrient decline and surface compaction upon disturbance.	Low permeability and high annual rainfall lead to waterlogging and soil compaction.

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