Soils on Basaltic Terrain

Qbg - Quaternary Basalt - Grey Duplex Soils | Qbm - Quaternary Basalt - Mixture | Qbr - Quaternary Basalt - Red Gradational Soils | Qbs - Quaternary Basalt - Stony Rises | | | Qvc - Quaternary Volcanic Cone

Qbg - Quaternary Basalt - Grey Duplex Soils

The soils derived from the Recent basalt flows fall into either the grey or red types, each quite different in agricultural quality. This unit represents only 0.2% of the Bungaree Shire or 0.5 km², but is a large component of the surrounding Shires. The grey duplex soils tend to become waterlogged and hard to work so they are used mainly for grazing with some cereal cropping, often as part of the pasture rotation.

COMPONENT	1	2	3
Proportion %	95	3	2
CLIMATE (Average) Rainfall mm	500 - 730
*Temperature °C	Average annual 12°C
*Seasonal growth limitations	Temperature less than 10°C May - September
GEOLOGY Age, growth	Pleistocene, basalt
TOPOGRAPHY Landscape	Extensive, slightly dissected plains
Elevation (range) m	482
Local relief (av.) m	2
Drainage pattern	Dendritic
Drainage density km/km²	2.2
Land form			-
Position on land form	Lo , gentle upper slopes	Depression	Stony rise
Slope (av.) ,%, slope shape	1-3 ; Straight	1-2 ; Straight	2-5 ; Convex
NATIVE VEGETATION Structure	Open forest
Dominant species	E. ovata, E. viminalis, E. rubida, E. obliqua		E. viminalis, E. rubida, E. obliqua, E. ovata
SOIL Parent material	In-situ weathered rock	Alluvium	In-situ weathered rock
Description	Mottled yellow, grey sodic duplex soil, coarse structure	Black clay soil, uniform texture coarse structure	Red shallow stony gradational soil
Surface texture	Clay loam	Clay	Clay loan
Permeability	Moderate-low	Moderate	High
Depth (av.) in	1.5		0.50
LAND USE	Grazing occasional cropping (cereal)		Grazing
SOIL DETERIORATION Critical land features	Hard setting surfaces, slowly permeable subsoils	Clay soils beside creeks	Slopes
Processes	Overland flow, periodic waterlogging	Waterlogging, streambank undercutting	Overland flow, leaching
Forms	Compaction of surfaces, sheet erosion	Stream bank erosion	Sheet erosion, nutrient decline

* Ballan figures

LAND UNIT: Quaternary basalt plain

COMPONENT: 1 – yellow grey duplex soil

MAP SYMBOL: Qbg 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	Poor	Soil drainage; low areas pond water; high plasticity clay; high shrink-swell	Urban (sewered)	Poor	Building houses; secondary roads (fair to poor: shallow excavations depending on rock & drainage).
Absorption fields	Poor	Soil drainage; slow percolation rate.	Small Farmlets 4 ha	Poor	Absorption fields – effluent; building houses; gravel roads; access tracks; small farm dams.
Secondary roads	Poor	Soil drainage; high plasticity clay; high shrink-swell.	Large Farmlets 16 ha	Fair	Absorption fields – effluent; building houses; gravel roads; access tracks; (fair: small farm dams
Gravel roads	Fair	Soil drainage; high plasticity clay.	Bush Blocks 4 ^ha.	Poor	Uncleared areas are rare: absorption fields – effluent; building houses; gravel roads; access tracks.
Access tracks	Poor	Low bearing capacity when wet; soil drainage; boggy.
Shallow excavations	Fair to poor	High plasticity clay; shrink-swell; soil drainage; depth to hard rock; basalt floaters
Small farm dams	Fair to poor	Depth to rock; basalt floaters; (Flat areas – storage excavation ratio; catchment problems).
Sewerage lagoons	Good	Basalt floaters
Topsoil - Quality	Fair	Too clayey
- Removal	Poor	Thin layer
- Resowing	Fair	Soil drainage; heavy textured subsoil
Sand - Quality	Very poor	No sand
- Operation
Gravel - Quality	Poor	Thin layer of iron stone gravel in high plastic clay.
- Operation
Grazing	Good to fair	Soil drainage, waterlogging of low areas which become boggy.
Cultivation	Fair to poor	Soil drainage; heavy textured hardsetting topsoil.
Clearing	Good

EFFECT OF SUBDIVISION OF THE LAND ON TOWN WATER SUPPLY
URBAN:	Urban development leads to a high pollution load from non-point sources which may be unacceptable in a domestic water supply catchment. However, there are no special features of this land component which would cause abnormal difficulties.
FARMLET:	Failure of absorption trenches will be a more severe risk to water supply if the land is subdivided more intensively. This is because: 1. Quantity of pollutant; there are more potential sources of pollution. 2. Sites: There will be less choice of disposal sites on small blocks. Some are likely to be restricted to particularly bad areas. However the risk of septic pollution will only be reduced, not removed by making the blocks larger. It would be preferable that effluent disposal did not rely on soil absorption (NOTE: percolation tests done in dry conditions often indicate rapid rates of absorption, while in winter the same sites show very slow rates – this may be related to cracking of the dry soil). If effluent disposal does not rely on soil absorption and is not likely to be a risk, then there are no special comments concerning water quality. Subdivision intensity can be increased.

LAND UNIT: Quaternary basalt plain

COMPONENT: 2 – Depression-black clay soil, uniform texture

MAP SYMBOL: Qbg 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	Poor to very poor	Soil drainage; surface flows; shrink-swell (very poor: flood prone)	Urban (sewered)	Poor to very poor	Building houses; secondary roads; shallow excavations.
Absorption fields	Very poor	Poor soil drainage; surface flows; seasonally low percolation rates.	Small Farmlets 4 ha	Very poor	Absorption fields - effluent; building houses; gravel roads; access tracks
Secondary roads	Poor	Soil drainage; surface flows; shrink-swell; high plasticity clay.	Large Farmlets 16 ha	Very poor	Absorption fields - effluent; building houses; access tracks.
Gravel roads	Poor	Soil drainage; surface flows; shrink-swell; high plasticity clay.	Bush Blocks 4 ^ha.	Very poor.	Absorption fields - effluent; building houses; gravel roads; access tracks. (Note: uncleared areas are rare).
Access tracks	Very poor	Soil drainage; low strength; boggy material.
Shallow excavations	Poor	Poor drainage; high plasticity clay.
Small farm dams	Fair to poor	Embankment material; storage/excavation ratio.
Sewerage lagoons	Poor	Proximity to drainage line; embankment material.
Topsoil - Quality	Poor	Too clayey.
- Removal	Good	Poorly drained; high plastic sub-soil.
- Resowing	Fair	No sand.
Sand - Quality	Very poor
- Operation
Gravel - Quality	Poor	Gravel deposits rare.
- Operation
Grazing	Fair	Soil drainage; severe pugging.
Cultivation	Poor	Soil drainage; surface flows; clayey topsoil.
Clearing	Fair	Surface flows.

EFFECT OF SUBDIVISION OF THE LAND ON TOWN WATER SUPPLY
URBAN:	The poor drainage, risk of shallow surface flows of water and in some areas, deep flooding, limits the capability of this component for urban development. These factors also present a serious risk to water supply quality.
FARMLET AND BUSH BLOCK:	There is a severe risk of pollution by effluent if disposal trenches are located on or near this component. If included in any farmlet subdivision, it should only be used for grazing. Housing and access tracks and roads should be kept well clear of this unit.

LAND UNIT: Quaternary basalt plain

COMPONENT:

MAP SYMBOL:

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	Poor	Depth to rock; boulders and surface stones	Urban (sewered)	Very poor	Shallow excavations (otherwise-poor: building houses; secondary roads
Absorption fields	Poor	Depth to rock; boulders and surface stones; variable soil drainage	Small Farmlets 4 ha	Poor	Small farm dams; absorption fields - effluent; building houses; gravel roads; access tracks.
Secondary roads	Poor	Depth to rook; boulders and surface stones.	Large Farmlets 16 ha	Poor	Small farm dams, absorption fields - effluent; building houses; access tracks
Gravel roads	Poor	Surface stones and boulders.	Bush Blocks 4 ha^.	Poor	Absorption fields - effluent, building houses; gravel roads; access tracks.
Access tracks	Poor	Surface stones and boulders.
Shallow excavations	Very poor	Depth to hard rock; boulders and surface stones.
Small farm dams	Very poor	Depth to hard rock; boulders; catchment requirements; excessive percolation rate.
Sewerage lagoons	Very poor	Depth to hard rock; boulders, excessive percolation rate of material.
Topsoil - Quality	Good	Clayey: stony.
- Removal	Poor	Surface stones and boulders, thin layer.
- Resowing	Fair	Surface stones and boulders.
Sand - Quality	Very poor	No sand.
- Operation
Gravel - Quality	Poor	Small quantities; stoniness; boulders.
- Operation
Grazing	Low	Surface stones; shallow soils.
Cultivation	Severe	Surface stones and boulders; undulating micro-relief.
Clearing	Moderate	Surface stones and boulders; undulating micro-relief affect

EFFECT OF SUBDIVISION OF THE LAND ON TOWN WATER SUPPLY
URBAN:	The physical constraints of shallow stony soils over hard rock limit the capability of this component for urban development. However, if these limitations are overcome, there are no special features of this component which would cause abnormal pollution problems, other than those normally associated with urban development.
FARMLET AND BUSH BLOCK:	Again, the constraints of shallow stony soils over hard rock will limit the capability of this component for most of the activities associated with farmlets. With sufficient financial input, most of these limitations can be overcome with. No abnormal effects on water quality other than those usually anticipated with intensive construction works. Sites for effluent absorption would require examination on this component.

Qbs - Quaternary Basalt - Stony Rises

This unit represents 0.7% of the survey area or 1.5 km². As the unit is characterised by the surface basalt boulders it has limited uses and is generally used for grazing, although possibly it could be used for tree crops provided that they were frost tolerant.

COMPONENT	1 100
Proportion %
CLIMATE (Average) Rainfall mm	760 - 800
*Temperature °C	Average annual 12.8°C
*Seasonal growth limitations	Temperature less than 10^oC May - September
GEOLOGY Age, growth	Pleistocene, basalt
TOPOGRAPHY Landscape	Scattered low stony rises in the north of the Shire
Elevation (range) m	500
Local relief (av.) m	1
Drainage pattern	-
Drainage density km/km²	-
Land form	Stony rise
Position on land form	-
Slope (av.) ,%, slope shape	1-2 ; Concave scarps. straight tops
NATIVE VEGETATION Structure	Woodland
Dominant species	E. viminalis, E. obliqua, E. radiata, E. ovata
SOIL Parent material	In-situ weathered rock
Description	Red shallow stony gradational soil
Surface texture	Clay loam
Permeability	High
Depth (av.) in	0.8
LAND USE	Grazing
SOIL DETERIORATION Critical land features	Slope, shallow, permeable soils
Processes	Overland flow, leaching
Forms	Sheet erosion, nutrient decline

LAND UNIT: Quaternary basalt – stony rises

MAP SYMBOL: Qbs

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	Poor	Depth to rock; boulders and surface stones.	Urban (sewered)	Very poor	Shallow excavations (otherwise-poor: building houses; secondary roads).
Absorption fields	Poor	Depth to rock; boulders and surface stones; variable soil drainage.	Small Farmlets 4 ha	Poor	Small farm dams; absorption fields - effluent; building houses; gravel roads; access tracks.
Secondary roads	Poor	Depth to rock; boulders and surface stones.	Large Farmlets 16 ha	Poor	Small farm dame; absorption_, fields; building houses; access tracks.
Gravel roads	Poor	Surface stones and boulders.	Bush Blocks 4 ha.	Poor	Absorption fields; building houses; gravel roads; access tracks.
Access tracks	Poor	Surface stones and boulders.
Shallow excavations	Very poor	Depth to hard rock; boulders and surface stones.
Small farm dams	Very poor	Depth to hard rock; boulders; catchment requirements; excessive percolation rate.
Sewerage lagoons	Very poor	Depth to hard rock; boulders; excessive percolation rate of material.
Topsoil - Quality	Good	Clayey; stony.
- Removal	Poor	Surface stones and boulders; thin layer.
- Resowing	Fair	Surface stones and boulders.
Sand - Quality	Very poor	No sand.
- Operation
Gravel - Quality	Poor	Small quantities; stoniness; boulders.
- Operation
Grazing	Fair	Surface stones; shallow soils
Cultivation	Very poor	Surface stones and boulders; undulating micro-relief.
Clearing	Fair	Surface stones and boulders; undulating micro-relief - affecting machinery operation.

EFFECT OF SUBDIVISION OF THE LAND ON TOWN WATER SUPPLY
URBAN:	The physical constraints of shallow stony soils over hard rock limit the capability of this component for urban development. However, if these limitations are overcome, there are no special features of this component which would cause abnormal pollution problems, other than those normally associated with urban development.
FARMLET AND BUSH BLOCK:	Again, the constraints of shallow stony soils over hard rock will limit the capability of this component for most of the activities associated with farmlets. With sufficient financial input, most of these limitations can be overcome with no abnormal effects on water quality other than those usually anticipated with intensive construction works. Sites for effluent absorption would require examination on this component.

Qbr - Quaternary Basalt - Red Gradational Soils

This unit forms the best agricultural land in the survey area and is generally used for potato cropping although it is highly versatile and could be used for a wide range of agricultural products. The unit represents 16.7% of the Shire and covers an area of 34.5 km². This land should be protected from further residential or industrial development and remain in its highly productive agricultural condition.

COMPONENT	1	2
Proportion %	96	4
CLIMATE (Average) Rainfall mm	780 - 840
*Temperature °C	Average annual 12^oC
*Seasonal growth limitations	Temperature less than 10°C May - September
GEOLOGY Age, growth	Pleistocene, basalt
TOPOGRAPHY Landscape	Undulating plains north of the Shire
Elevation (range) m	660
Local relief (av.) m	5
Drainage pattern	Dendritic
Drainage density km/km²	1.6
Land form	Undulating plain
Position on land form	Gentle slope	Depression
Slope (av.) ,%, slope shape	1-6 ; Convex-	1-2 ; Straight
NATIVE VEGETATION Structure	Open forest
Dominant species	E. viminalis, E. radiata, E. obliqua
SOIL Parent material	In-situ weathered rock and unconsolidated sediments
Description	Red gradational soil, fine structure	Mottled yellow duplex soil, coarse structure
Surface texture	Clay loam	Clay loam
Permeability	High	Moderate-low
Depth (av.) in	2	1.5
LAND USE	Cropping (potatoes), grazing	Grazing, cropping (cereal)
SOIL DETERIORATION Critical land features	Slopes	Low permeability, hard setting surfaces
Processes	Overland flow, leaching	Waterlogging
Forms	Sheet erosion, wind erosion, nutrient decline	Compaction

LAND UNIT: Quaternary basalt – red gradational soil

COMPONENT: 1 – Gentle slopes – red gradational soil

MAP SYMBOL: Qbr 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	Good	Load bearing capacity when wet; shrink-swell.	Urban (sewered)	Good
Absorption fields	Good		Small Farmlets 4 ha	Poor	Small farm dams; (otherwise good).
Secondary roads	Good	Load bearing capacity when wet.	Large Farmlets 16 ha	Fair	Small farm dams; (otherwise good) (note – larger blocks are more likely to contain a satisfactory dam site).
Gravel roads	Good	Load bearing capacity when wet.	Bush Blocks 4 ha.	Very good	Few areas of bush.
Access tracks	Good to fair	Load bearing capacity when wet; (boggy in low areas).
Shallow excavations	Good
Small farm dams	Poor	High percolation rate.
Sewerage lagoons	Poor	High percolation rate.
Topsoil - Quality	Good	Clayey, (but well structured).
- Removal	Good
- Resowing	Good
Sand - Quality	Very poor	No sand deposits.
- Operation
Gravel - Quality	Very poor	No gravel deposits
- Operation
Grazing	Very good
Cultivation	Good	High phosphate fixation; slope; topsoil wash on long, cultivated slopes.
Clearing	Very good

EFFECT OF SUBDIVISION OF THE LAND ON TOWN WATER SUPPLY
URBAN:	Urban development leads to a high pollution load from non-point sources which may be unacceptable in a domestic water supply catchment. However, there are no special features of this land component which would cause abnormal difficulties.
FARMLET & BUSH BLOCK:	This component has no special features which will cause abnormal problems concerning water quality. However, increasing the numbers of roads, tracks, houses and effluent disposal points will increase the levels of pollution.

LAND UNIT: Quaternary basalt

COMPONENT: 2 – Depression: mottled yellow, red gradational soil

MAP SYMBOL: Qbr 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; surface ponding; shrink swell.	Urban (sewered)	Fair to poor	Building houses; secondary roads; shallow excavations.
Absorption fields	Poor	Soil drainage; water logging & surface flows in some areas; slow percolation rate	Small Farmlets 4 ha	Poor	Absorption fields - effluent; access tracks; gravel roads; building houses.
Secondary roads	Fair to poor	Soil drainage; high plasticity clay; shrink-swell	Large Farmlets 16 ha	Poor	Absorption fields - effluent; access tracks; building houses
Gravel roads	Fair to poor	Soil drainage; high plasticity clay.	Bush Blocks 4 ha.	Poor – little uncleared land.	Uncleared areas are rare: absorption fields - effluent; access tracks; gravel roads; building houses.
Access tracks	Poor	Low bearing capacity when wet; soil drainage; boggy.
Shallow excavations	Fair	High plasticity clay; shrink-swell; soil drainage.
Small farm dams	Good	High plasticity clay; shrink-swell.
Sewerage lagoons	Good
Topsoil - Quality	Fair	Hard setting; heavy texture.
- Removal	Fair	Thin layer.
- Resowing	Fair	Poor drainage; high plasticity subsoil.
Sand - Quality	Very poor	No sand
- Operation
Gravel - Quality	Very poor	No gravel.
- Operation
Grazing	Good to fair	Soil drainage.
Cultivation	Fair to poor	Low permeability; poor drainage; heavy textured topsoil; erosion risk; proximity to drainage lines.
Clearing	Fair	Proximity to drainage lines.

EFFECT OF SUBDIVISION OF THE LAND ON TOWN WATER SUPPLY
URBAN:	Urban development leads to a high pollution load from non-point sources which may be unacceptable in a domestic water supply catchment. However, there are no special features of this land component which would cause abnormal difficulties, other than its proximity to watercourses.
FARMLET:	This component occurs on the lower slopes and drainage lines of the land system and is prone to poor drainage, water-logging and often surface flows. Severe risk of pollution by effluent if disposal relies on soil absorption. Disposal trenches will be far less prone to failure if located on component 1 of this land system (i.e. red gradational soils further up the slope).
BUSH BLOCK:	As for farmlets (Note-uncleared areas are rare).

Qbm - Quaternary Basalt - Mixture

This unit consists of a dark red gradational soil and a mixture of the good red gradational soils on the crest and upper slopes and a poorer grey sodic duplex soil on the lower slopes and in depressions. The area represents 26.1% of the survey area (53.9 km². It is located mainly in the central part of the Shire, and is generally used for cropping. However only the better red gradational soils are used for row crops, the remainder being used for cereal crops or grazing.

COMPONENT	1	2	3
Proportion %	34	33	33
CLIMATE (Average) Rainfall mm	800 - 840
*Temperature °C	Average annual 12^oC
*Seasonal growth limitations	Temperature less than 10^oC May - September
GEOLOGY Age, growth	Pleistocene, basalt
TOPOGRAPHY Landscape	Slightly dissected plain north of the Shire
Elevation (range) m	280
Local relief (av.) m	4
Drainage pattern	Dendritic
Drainage density km/km²	2.3
Land form	Undulating plain
Position on land form	Crest and upper slope	Mid slope	Lower slope and depression
Slope (av.) ,%, slope shape	1-6 ; Convex	2-7 ; Straight	1-2 ; Concave
NATIVE VEGETATION Structure	Open forest
Dominant species	E. viminalis, E. obliqua, E. radiata
SOIL Parent material	In-situ weathered rock		Unconsolidated sediments
Description	Red gradational soil , fine structure	Dark red gradational soil, fine structure	Mottled yellow sodic duplex soil, coarse structure
Surface texture	Clay loam	Loam	Clay loam
Permeability	High	High	Moderate-low
Depth (av.) in	2	1.5	1.5
LAND USE	Cropping, grazing (potatoes)	Cropping (cereal), grazing, cropping (potatoes)	Grazing, cropping
SOIL DETERIORATION Critical land features	Slope, exposure	Slope, hard setting surfaces	Low permeability, hard setting surfaces
Processes	Leaching, overland flow	Leaching, overland flow	Waterlogging
Forms	Sheet and wind erosion, nutrient decline	Compaction, wind & sheet erosion, nutrient decline	Compaction

LAND UNIT: Quaternary basalt - mixture

COMPONENT: 1 – Crests – Red gradational soils

MAP SYMBOL: Qbm 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	Good	Load bearing capacity when wet; shrink-swell	Urban (sewered)	Good
Absorption fields	Good		Small Farmlets 4 ha	Poor	Small farm dams (otherwise good)
Secondary roads	Good	Load bearing capacity when wet	Large Farmlets 16 ha	Fair	Small farm dams (otherwise good) (Note- larger blocks are more likely to contain a satisfactory dam site)
Gravel roads	Good	Load bearing capacity when wet	Bush Blocks 4 ha.	Very good	Few areas of bush
Access tracks	Good to fair	Load bearing capacity when wet (boggy in low areas)
Shallow excavations	Good
Small farm dams	Poor	High percolation rate
Sewerage lagoons	Poor	High percolation rate
Topsoil - Quality	Good	Clayey (but well structured)
- Removal	Good
- Resowing	Good
Sand - Quality	Very poor	No sand deposits
- Operation
Gravel - Quality	Very poor	No gravel deposits
- Operation
Grazing	Very good
Cultivation	Good	High phosphate fixation; slope; topsoil wash
Clearing	Very good	on long, cultivated slopes

EFFECT OF SUBDIVISION OF THE LAND ON TOWN WATER SUPPLY
URBAN:	Urban development leads to a high pollution load from non--point sources which may be unacceptable in a domestic water supply catchment. However, there are no special features of this land component which would cause abnormal difficulties.
FARMLET & BUSH BLOCK:	This component has no special features which will cause abnormal problems concerning water quality. However, increasing the numbers of roads, tracks, houses and effluent disposal points will increase the levels of pollution.

LAND UNIT: Quaternary basalt - mixture

COMPONENT: 2 – Mid-slope – Dark red gradational soils

MAP SYMBOL: Qbm 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	Good	Low shrink-swell.	Urban (sewered)	Good
Absorption fields	Good		Small Farmlets 4 ha	Pair	Dams (otherwise - very good).
Secondary roads	Good	Low bearing capacity when wet.	Large Farmlets 16 ha	Fair	Dams
Gravel roads	Good	Low bearing capacity when wet.	Bush Blocks 4 ha.	Very good	Very little uncleared land.
Access tracks	Good	Low bearing capacity when wet.
Shallow excavations	Good
Small farm dams	Fair	Moderate to rapid percolation rate.
Sewerage lagoons	Poor	Excessive percolation rate.
Topsoil - Quality	Good	Clayey (but friable).
- Removal	Good
- Resowing	Good
Sand - Quality	Very poor	No sand.
- Operation
Gravel - Quality	Very poor	No gravel.
- Operation
Grazing	Very low
Cultivation	Low to moderate	High phosphate fixation; slope; topsoil wash on long, cultivated slopes; proximity to drainage lines; soil structure is poorer than for component 1 (crests).
Clearing	Very low

EFFECT OF SUBDIVISION OF THE LAND ON TOWN WATER SUPPLY
URBAN:	Urban development leads to a high pollution load from non-point sources which may be unacceptable in a domestic water supply catchment. However, there are no special features of this land component which would cause abnormal difficulties.
FARMLETS &BUSH BLOCKS:	This component has no special features which will cause abnormal problems concerning water quality. However, increasing the numbers of roads, tracks, houses and effluent disposal points will increase the levels of pollution.

LAND UNIT: Quaternary basalt - mixture

COMPONENT: 3 – Lower slope – yellow duplex soil

MAP SYMBOL: Qbm 3

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; surface ponding; (some areas flood).	Urban (sewered)	Fair to poor	Building houses; secondary roads; shallow excavations
Absorption fields	Poor	Soil drainage; water logging & surface flows in some areas; slow percolation rate.	Small Farmlets 4 ha	Poor	Absorption fields – effluent; building houses; gravel roads; access tracks.
Secondary roads	Fair to poor	Soil drainage; high plasticity clay; shrink-swell.	Large Farmlets 16 ha	Poor	Absorption fields – effluent; building houses; access tracks.
Gravel roads	Fair to poor	Soil drainage; high plasticity clay; (some areas flood or pond water).	Bush Blocks 4 ha.	Poor	Uncleared areas are rare; absorption fields – effluent; building houses; gravel roads & access tracks.
Access tracks	Poor	Low bearing capacity when wet; soil drainage; boggy.
Shallow excavations	Fair	High plasticity clay; shrink-swell; soil drainage.
Small farm dams	Good	High plasticity clay; shrink-swell.
Sewerage lagoons	Good
Topsoil - Quality	Fair	Hard setting; heavy texture.
- Removal	Poor	Thin layer.
- Resowing	Fair	Poor drainage; high plasticity subsoil.
Sand - Quality	Very poor	No sand.
- Operation
Gravel - Quality	Very poor	No gravel.
- Operation
Grazing	Good to fair	Soil drainage; heavy textured soil; hard setting.
Cultivation	Fair to poor	Lower permeability; poor drainage; heavy textured topsoil; erosion risk; proximity to drainage lines.
Clearing	Fair	Surface wash before pasture establishment; proximity to creeks

EFFECT OF SUBDIVISION OF THE LAND ON TOWN WATER SUPPLY
URBAN:	Urban development leads to a high pollution load from non-point sources which may be unacceptable in a domestic water supply catchment. However, there are no special features of this land component which would cause abnormal difficulties, other than its proximity to watercourses.
FARMLET:	This component occurs on the lower slopes and drainage lines of the land system and is prone to poor drainage, waterlogging and often, surface slows. Severe risk of pollution by effluent if disposal relies on soil absorption. Disposal trenches will be far less prone to failure if located on components 1 and 2 of this land system (i.e. red gradational and dark red gradational soils further up the slopes).
BUSH BLOCKS	As for farmlets (NOTE: uncleared areas are rare).

Qvc - Quaternary Volcanic Cone

This unit represents 1.6% of the survey area or 3.3 km². The cones are the points of origin of most of the recent basalt flows and they vary slightly according to their lithology. Some cones are extremely steep whereas others barely rise above the basalt flow. The steeper ones are largely forested and in public ownership whereas the gentler ones are used for grazing.

COMPONENT	1
Proportion %	100
CLIMATE (Average) Rainfall mm	500 - 965
*Temperature °C	Average annual 12°C
*Seasonal growth limitations	Temperature less than 10°C May - September
GEOLOGY Age, growth	Pleistocene; basalt, scoria tuff
TOPOGRAPHY Landscape	Scattered volcanic cones
Elevation (range) m	600
Local relief (av.) m	60
Drainage pattern	Radial & Shut flow (Poorly developed channels)
Drainage density km/km²
Land form	Volcanic cone
Position on land form	Slope and crest
Slope (av.) ,%, slope shape	5-40 ; Straight
NATIVE VEGETATION Structure	Open forest
Dominant species	E. viminalis, E. radiata
SOIL Parent material	In-situ weathered rock
Description	Stony red gradational soil
Surface texture	Clay loam
Permeability	High
Depth (av.) in	1
LAND USE	Grazing, forestry
SOIL DETERIORATION Critical land features	Steep slopes
Processes	Overland flow, leaching
Forms	Rill and sheet erosion, nutrient decline

LAND UNIT: Quaternary volcanic cones

MAP SYMBOL: Qvc

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	5-10% Fair 10-15% Poor	Slope-possible landslips; depth to rock. 15+% Very poor	Urban (sewered)	Fair to very poor	Building houses; secondary roads; shallow excavations (depends on slope & landslip risk).
Absorption fields	8-15% Fair 15+% Poor	Slope-layout and construction	Small Farmlets 4 ha	Poor to very poor	Building houses; gravel roads; access tracks: small farm dams; absorption fields - effluent).
Secondary roads	8-12% Fair 12-20% Poor	Slope-soil slumps; depth to rook. 20+% Very poor.	Large Farmlets 16 ha	Poor to very poor	Building houses; access tracks; small farm dams.
Gravel roads	8-15% Fair 15-20% Poor	Slope-construction; rook; batters slump. 20+% Very poor.	Bush Blocks 4 ha.	Poor to very poor	House foundations; roads; (few uncleared areas).
Access tracks	8-15% Fair 15-25% Poor	Slope-erosion & use. 25+% Very poor.
Shallow excavations	5-10% Fair 10-20% Poor	Slope; depth to rock. 20+% Very poor.
Small farm dams	Very poor	Slope; rapid percolation rate; depth to rock.
Sewerage lagoons	Very poor	Slope; rapid percolation rate; depth to rock.
Topsoil - Quality	Good	Clayey (but well structured).
- Removal	Good to very poor	Slope-operations & access.
- Resowing	Fair to poor	Slope-machine operation & erosion risk.
Sand - Quality	Very poor	No sand.
- Operation
Gravel - Quality	Variable	Scoria
- Operation	Variable	Slope-access & reclamation
Grazing	Good to poor	Depending on slope-sheet erosion; & stock management.
Cultivation	Fair to very poor	Depending on slope-sheet and rill erosion; &, machine operation.
Clearing	Good to poor	Depending on slops.

EFFECT OF SUBDIVISION OF THE LAND ON TOWN WATER SUPPLY
URBAN, FARMLET and BUSH BLOCKS:	Although the water supply may not be greatly affected by development of the cones, the limitations caused by steep slopes and potential for landslips and soil slumping will require consideration.

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