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Maffra 1 (M1)

A study of the land in the Catchment of Gippsland Lakes - Vol 2 - land system Maffra1- geoArea: 161 sq. km (0.8%)

This land system occurs on the modern river flood plains that, whilst having an active flood regime, are located above the levels containing major river channels. These alluvial plains have complex patterns of irregular and anastomosing flow paths and channels, with many small flanking levees and intervening clay flats. The land forms and materials of the flood plains within the different stream systems vary, due to differences in flow regime and catchment lithology. Surface materials are mostly clayey and pervious but may be silty or sandy, particularly in the east. Also, in some upstream tracts such as those of the Mitchell and Macalister Rivers, reddish levee materials with coarser textures and relatively free drainage predominate. The deposition of these coarser sediments may reflect the greater competence of the streams where they emerge from the East Victorian Uplands. Some of these regional differences are identified at component level.
A study of the land in the Catchment of Gippsland Lakes - Vol 2 - land system Maffra1- image
Poorly drained depressions on the river flood plain are characteristic of Maffra I land system.
Soils are variable due mainly to differences in soil drainage and in the length of time since alluvial deposition. Deposition is still occurring in some areas but probably ranges up to about 10,000 years ago in others.

The river terraces usually have an abundant supply of moisture derived from relatively high water tables and periodic flooding, although the rainfall is low to moderate. Abundant moisture and youthful clayey and silty parent materials with moderate to high levels of plant nutrients has generally meant a high biomass production. As a result most of the older soils have high levels of organic matter. Where drainage is good, these soils have developed crumb structure and friable topsoils in addition to accumulating organic matter. Where waterlogging is common, the soils may be strongly mottled throughout the profile or in the lower horizons only.

Very young soils (components 3 and 5) and those where there is lower available moisture due to greater depths to the water table (component 4) have accumulated less organic matter. Brown soils with incomplete development and even younger brown soils with negligible development of structure and colour differentiation, are particularly prevalent along the Tambo and Nicholson Rivers. Mature reddish soils with structureless subsoils and with blocky-structured alkaline subsoils appear to be typical of upstream levees and outwash fans, possibly because coarser sediments and greater depth to water table lead to oxidation of minerals as well as humus.

The soils are generally fertile and have a low erosion hazard but they are susceptible to compaction, particularly when wet. A low salinity hazard, which may increase to moderate in localised areas exists in the area between Valencia Creek and Lake Wellington due to moderately deep groundwater of low to moderate salinity. The native vegetation, probably an E. tereticornis grassy open forest 11. has been almost entirely removed.

CLIMATE
Rainfall, mean (mm)
Temperature, mean (C)
Seasonal growth limitations

Annual 500 - 800; lowest July (30 - 50), highest October (50 - 80)

Annual 12 - 14: lowest July (8 - 10), highest February (19 - 21)
Temperature <10C (av.): June - August
Rainfall < potential evapotranspiration: November - March
GEOLOGY
Age, lithology

Holocene alluvium of clays, silts and sands
PHYSIOGRAPHY
Landscape
Elevation range (m)
Relative relief (m)
Drainage pattern
Drainage density (km/km2)

Active alluvial plains with a complex of levees. ephemeral flow paths and channels

20 - 60
0 - 5
Irregular and braided
2.6
PRESENT LAND USECleared: grazing of beef and dairy cattle on improved, often irrigated pastures; some cropping: some apiculture

A study of the land in the Catchment of Gippsland Lakes - Vol 2 - land system Maffra1- csA study of the land in the Catchment of Gippsland Lakes - Vol 2 - land system Maffra1- graph

LAND COMPONENT
Percentage of land system
Diagnostic features
1
35
Flood plains with better subsoil drainage
2
15
Flood plains with poorer subsoil drainage (mainly Thomson River and Freestone Creek)
3
15
Flood plains with youthful undifferentiated soils (mainly Tambo and Nicholson Rivers)
4
30
Low levees and undulating outwash areas, with either reddish (upstream parts of flood plains) or greyish brown soils
5
5
Ephemeral channels and flowpaths, often poorly drained
PHYSIOGRAPHY
Slope %, typical and (range)
Slope shape
I. (0 - 3)
Straight but uneven
2,(0-4)
Straight
1, (0 - 3)
Straight but uneven
2, (0 - 4)
Convex, some concave
1, (0 - 5)
Concave
SOIL
Parent material
Mainly silty and clayey alluvium; some sandy sediments
Description
Mainly black clay loam topsoil grading into dark brown or reddish brown clay subsoil, often mottled at depth and neutral to alkaline
Mainly very dark grey to dark brown clay loam sometimes mottled, grading into dark grey to dark brown mottled clay subsoil
Limited observations — very dark greyish brown sandy loam to silty loam topsoil grading into similar coloured, sometimes mottled sand to clay loam subsoil
Limited observations — dark greyish brown or dark reddish brown sandy loam to sandy clay loam topsoil grading into similar coloured, variably textured subsoil
Limited observations — probably undifferentiated greyish brown soil of variable texture
Classification
Prairie Soils
Mostly Um6.21, Uf6.11, Uf6.12
Wiesenboden. some Humic Gleys
Uf6.11, Gn3.43, Gn4.31, Gn4.51
Alluvial Soils, some
Minimal Prairie Soils
Um6.21, Uc5.21, Uc5.23
Minimal Prairie Soils.
Red-brown Earths
Um5.52, Um6.21, Gn4.13
Alluvial Soils
Uc1.44, Uc5.23
Surface texture
Sandy loam to light clay
Mostly clay loam
Sandy loam to silty loam
Sandy loam to sandy clay loam
Variable
Surface consistence
Friable to firm when moist
Friable when moist
Friable to firm when moist
-
Depth (m)
>2.0
>2.0
>2.0
>2.0
Nutrient status
Moderate to high
Moderate
Moderate
-
Available soil water capacity
Moderate to high
Moderate
Moderate
-
Perviousness to water
Slow
Slow to rapid
Slow to rapid
-
Drainage
Somewhat poor to good
Poor to somewhat poor
Somewhat poor to good
Moderately good to good
Poor
Exposed stone (%)
0
0
0
0
0
Sampled profile number
27
26, 40, 44
24
42
-
NATIVE VEGETATION
Structure of vegetation and characteristic species of dominant stratum
(+ Predominant species)
Grassy open forest II: E. tereticornis+, E. polyanthemos and E. viminalis occasionally observed
Clearing has made it difficult to determine if any other predominant or associated tree species

Disturbance
Affected process and trend
Primary resultant deterioration
Casual activities
Primary off-site process
Form
Susceptibility of components
Incidence with components
    Alteration of vegetation:


    - reduction in leaf area, rooting depth and/or perenniality
    Reduced transpiration resulting in:
a) increased deep percolation



b) raised saline groundwater table


Nutrient loss




Salting, waterlogging


Not determined




2; low
2; moderate


Not determined




Common



Removal of trees




Usually after the removal of trees from steeper land. Reduced plant-water use within the catchment.


Increased movement of water to groundwater, increased base-flow of streams.

Increased run-on and ponding in lowest areas.
    Increased exposure of surface soil
    Increased overland flow and soil detachment
    Sheet and rill erosion
    4; low-moderate
    Uncommon
    Overgrazing, road and dam building and other earth-moving activities, trafficking by stock and vehicles
    Increased flash flows and sediment load.
    Increased physical pressure on soil
    Increased compaction

With

Reduced infiltration
    Structure decline


Sheet and rill erosion
    2,5; moderate-high
1; low-moderate

3,4; low
    Not determined



Not determined
    Increased trafficking and cultivation, overgrazing, export of organic matter.

As for sheet and rill erosion above.
    -



Increased flash flows
    Increased soil disruption
    Increased soil break-up
    Gully erosion
    4; low
    Not determined
    As for sheet and rill erosion above.
    Increased sediment load and turbidity in rivers.
Comments: No observations of deterioration
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