Soils on Granitic Terrain

Dgn - Devonian Granite

This unit represents 1.2% of the survey area or 2.5 km². The main locations are around Kirk's and Gong Gong Reservoirs. Some parts are used for sand removal but it is mostly used for grazing. The area in the catchment to Gong Gong Reservoir is used for a pine plantation.

This can be quite a hazardous unit unless it receives careful management.

COMPONENT	1	2
Proportion %	30	70
CLIMATE (Average) Rainfall mm	500 - 560
*Temperature °C	Average annual 12°C
*Seasonal growth limitations	Temperature less than 10°C May - September
GEOLOGY Age, growth	Devonian; granite, granodiorite	Quaternary; wash-gravel sand and clay
TOPOGRAPHY Landscape	Hilly and rolling country in the centre south of the Shire
Elevation (range) m	520
Local relief (av.) m	30
Drainage pattern	Dendritic
Drainage density km/km²	4.8
Land form	Hill	Fan and terrace
Position on land form	Crest and slope	Drainage line
Slope (av.) ,%, slope shape	2-10 ; Convex	1-3 ; Straight
NATIVE VEGETATION Structure	Open forest
Dominant species	E. viminalis E. radiata	E. ovata, E. obliqua, E. radiata
SOIL Parent material	In-situ weathered rock	Unconsolidated wash
Description	Mottled yellow red duplex soil
Surface texture	Sandy loam
Permeability	Moderate	Moderate-low
Depth (av.) in	1	1
LAND USE	Grazing
LAND USE	Soil and gravel stripping
SOIL DETERIORATION Critical land features	Moderate elope, low permeability, hard setting surfaces	Poor drainage, low permeability, hard setting surfaces, dispersible soils
Processes	Overland flow, subsurface flow, deep seepage, leaching of salts	Accumulation of salts, overland flow and waterlogging, subsurface flow
Forms	Rill & gully erosion, sheet erosion	Salting, gully erosion, compaction

* Ballan figures

LAND UNIT: Devonian granodiorite

COMPONENT: 1 – Hills – Mottled yellow, red duplex soils

MAP SYMBOL: Dgn 1

CAPABILITY OF THE LAND TO SUPPORT VARIOUS ACTIVITIES			CAPABILITY OF THE LAND TO SUPPORT SUBDIVISION
ACTIVITY	RATING	MAJOR LIMITING FEATURES OF THE LAND	SUBDIVISION TYPE	RATING	MAJOR LIMITING ACTIVITIES
Building houses	Fair	Erosion during development; depth to hard rook.	Urban (sewered)	Fair	Shallow excavations; building houses: secondary roads (during development stage)
Absorption fields	Fair	Variable percolation rates; usually between moderately slow and moderately rapid.	Small Farmlets 4 ha	Fair	Small farm dams; gravel roads; access tracks.
Secondary roads	Fair	Erosion during construction; depth to hard rock.	Large Farmlets 16 ha	Fair	Small farm dams; access tracks.
Gravel roads	Fair	Erosion of table drains and batters.	Bush Blocks 4 ha.	Fair	Gravel roads; access tracks.
Access tracks	Fair	Erosion of track surface: table drains and batters.
Shallow excavations	Fair	Depth to hard rock.
Small farm dams	Fair	Depth to hard rook or sand layers.
Sewerage lagoons	Fair to poor	Slope; depth to hard rook.
Topsoil - Quality	Fair to good	Hard setting.
- Removal	Fair	Thin layer.
- Resowing	Poor	Infertile; easily eroded sub-soil layers.
Sand - Quality	Variable	Areas of granitic sand of varying quality. Thickness of deposit and depth.
- Operation
Gravel - Quality	Poor	No gravel.
- Operation
Grazing	Good to fair	Moderate sheet erosion with overgrazing
Cultivation	Fair to poor	Slope; low permeability of clay and hardsetting structureless topsoil results in a moderate risk of rill and sheet erosion.
Clearing	Fair	Erosion prior to pasture establishment; salting of lower land.

EFFECT OF SUBDIVISION OF THE LAND ON TOWN WATER SUPPLY
URBAN:	Silt loss from development sites will be a problem unless earthworks are correctly managed. Land disturbance guidelines should be followed.
FARMLET:	Erosion of tracks and gravel roads will be the main potential problem.
BUSH BLOCKS:	As for farmlets

LAND UNIT: Devonian granodiorite

COMPONENT: 2 – Fans & terraces – mottled yellow, red duplex soil

MAP SYMBOL: Dgn 2

CAPABILITY OF THE LAND TO SUPPORT VARIOUS ACTIVITIES			CAPABILITY OF THE LAND TO SUPPORT SUBDIVISION
ACTIVITY	RATING	MAJOR LIMITING FEATURES OF THE LAND	SUBDIVISION TYPE	RATING	MAJOR LIMITING ACTIVITIES
Building houses	Fair to poor	Soil drainage; temporary perched watertables.	Urban (sewered)	Fair to poor	Secondary roads; building houses; shallow excavations.
Absorption fields	Fair to poor	Impermeable B horizon; imperfect to poor drainage; temporary perched watertables.	Small Farmlets 4 ha	Fair to poor	Absorption fields - effluent; (otherwise-fair: gravel roads; access tracks; building houses).
Secondary roads	Fair to poor	Soil drainage; temporary perched watertables	Large Farmlets 16 ha	Fair to poor	Absorption fields - effluent; (otherwise-fair: access tracks; building houses).
Gravel roads	Fair	Soil drainage; erosion of table drains.	Bush Blocks 4 ha.	Fair.	Absorption fields - effluent; gravel roads; access tracks; building houses.
Access tracks	Poor	Soil drainage; A2 horizon-becomes "spewy" - boggy.
Shallow excavations	Fair	Soil drainage (seasonal).
Small farm dams	Good
Sewerage lagoons	Fair	Slope - economical construction.
Topsoil - Quality	Good	Hard setting.
- Removal	Fair	Thin layer.
- Resowing	Poor	Infertile subsurface layers: some salting.
Sand - Quality	Good to poor	Variable quality.
- Operation	Fair	Thickness of overburdens.
Gravel - Quality	Very poor	No gravel.
- Operation
Grazing	Fair to Good	Soil drainage; minor salting in some areas
Cultivation	Fair	Surface water flows; erosion; possible salting; hardsetting topsoil; impermeable clay; soil drainage.
Clearing	Fair to good	Erosion prior to pasture establishment.

EFFECT OF SUBDIVISION OF THE LAND ON TOWN WATER SUPPLY
URBAN:	Soils are erodible and, though the slopes are gentler than in component 1 (the hills), silt from development will be a problem unless earthworks are correctly managed. The seasonally wet boggy nature of the bleached A2 horizon will necessitate construction works to be during the drier months.
FARMLET:	Although most soils have fairly permeable A horizons, there are many poorly drained areas in which absorption fields will not function. Thee is frequently a temporary watertable perched on the clay for many weeks after heavy rain. The factors responsible are the impermeable B horizon (clay), the permeable A horizon and the gentle slopes. Site inspections for absorption trenches would be required.
BUSH BLOCKS:	As for farmlets, except that soil drainage tends to be better under forest.

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