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Yinnar (Yr)

A study of the land in the Catchment of Gippsland Lakes - Vol 2 - land system Yinnar- geoArea: 113 sq. km (0.6%)

This land system is confined to almost flat, alluvial terraces in the more humid parts of the Western lowlands. These terraces appear to be of similar age to those of Valencia land system but the materials are derived from Cretaceous sediments. There is some evidence of relict fluviatile land forms.

The deposits are mainly silts and clays with minor admixtures of sand. The soils are diverse due mainly to variations in drainage which ranges from very poor to somewhat poor. This variation can be related to differences in local relief, to the permeability of layers within or below the soils and also to differences in seepage and run-off from adjacent higher land. Duplex soils tend to occupy the better-drained sites and gradational soils the more poorly-drained parts. In all soils the depth of periodic saturation by water appears to be reflected in the depth and degree of mottling. Erosion hazards are minor but because of periodic high water tables, soil structure can be readily impaired by trampling and trafficking. Some subsurface horizons are fluid when wet.

The original vegetation, now almost entirely cleared, appears to have been mainly open forest II or III dominated by E. bridgesiana, E. ovata, E. radiata and E. viminalis.
A study of the land in the Catchment of Gippsland Lakes - Vol 2 - land system Yinnar- image
A broad alluvial plain backed by the Strzelecki Ranges (almost visible) which have provided much of the alluvium.

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

    Annual 700 - 1200; lowest January (40 - 70), highest October (70 - 100)

    Annual 12 - 14; lowest July (8 - 10), highest February (19 - 21)
    Temperature <10C (av.): June - August
    Rainfall < potential evapotranspiration: November – March
GEOLOGY
Age, lithology
PHYSIOGRAPHY
Landscape
Elevation range (m)
Relative relief (m)
Drainage pattern
Drainage density (km/km2)

    Almost flat alluvial plains

    20 - 100
    0 - 5
    Dendritic
    0.9
PRESENT LAND USE
    Mostly cleared: grazing of beef and dairy cattle and fat lambs on improved pastures; some apiculture

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

LAND COMPONENT
Percentage of land system
Diagnostic features
1
50
Broad plains
2
40
Slightly depressed parts of
plains with poorer drainage than
in component 1
3
5
Minor drainage depressions and adjacent
steep slopes
4
5
Narrow upstream terraces,
no longer flood prone
PHYSIOGRAPHY
Slope %, typical and (range)
Slope shape
1, (0 - 2)
Straight
1, (0 - 2)
Slightly concave
Variable, (0 - 30)
Concave
1, (0 - 2)
Straight
SOIL
Parent material
Mainly fine-textured alluvial material, mostly derived from surrounding Cretaceous mudstone, shale and sandstone loam
Description
Dark greyish brown sandy loam to light clay topsoil with gradual or abrupt change to grey, light yellowish brown or pale brown clay subsoil. Profiles often moderately to slightly acid in the top, becoming neutral at depth. All soils with sign of poor drainage such as grey colours and mottling, with the extent of mottling being indicative of severity
Duplex and gradational soils with upper topsoil often whole coloured
Mainly gradational soils with entire profile commonly mottled; high water tables are common throughout the year
Duplex soils with upper topsoil generally whole coloured
Classification
Yellow Podzolic Soils,
Wiesenboden, Solodic Soils
Dy3. - , Gn3. - , Gn4.5-
Wiesenboden; some Humic Gleys, Gleyed Podzolic Soils, Solodic Soils
Gn3.72, Gn3.92, Gn3.93, Gn3.95, Gn4.51, Gn4.52, Uf6.61, Dy3.22
Yellow Podzolic Soils; some,
Gleyed Podzolic Soils, Solodic Soils
Mostly Dy3.11, also Dy3.41, Dy3.42
Surface texture
Variable sandy loam to light clay
Variable; sandy loam to light clay
Sandy loam to loam; may be clay loam
Surface consistence
Slightly hard to hard when dry
Slightly hard to hard when dry
Generally slightly hard when dry
Depth (m)
>2.0
>2.0
>2.0
Nutrient status
Moderate
Moderate
Moderate
Available soil water capacity
Moderate
Moderate
Moderate
Perviousness to water
Slow
Slow
Slow
Drainage
Poor to somewhat poor
Very poor to poor
Poor to somewhat poor
Exposed stone (%)
0
0
0
Sampled profile number
-
-
-
NATIVE VEGETATION
Structure of vegetation and
characteristic species of
dominant stratum
(+ Predominant species)
Open forest II, III, sometimes shrubby or sedgey: Pure or mixed stands of E. ovata, E. viminalis, E. radiata and occasionally E. bridgesiana; in addition, E. obliqua grows in component 4

Disturbance
Affected process and trend
Primary resultant deterioration
Causal activities
Primary off-site process
Form
Susceptibility of
components
Incidence within
components
Alteration of vegetation:
— reduction in leaf area, rooting
depth and/or perenniality
Reduced transpiration,
resulting in a raised watertable
Waterlogging1,4; low
2; moderate
Common; in low-lying areasReduced plant water-use in the catchmentIncreased movement of water to groundwater and raised watertables
Increased exposure of surface soilIncreased overland flow and soil detachmentSheet and rill erosion3; low - moderateUncommonClearing, burning, overgrazing, road and dam building and other earth-moving activities, trafficking by stock and vehicles.Increased ponding and sedimentation in low-lying areas
Increased physical pressure on soilIncreased compaction

With


Reduced infiltration
Structure decline




Sheet and rill erosion
1,4; low – moderate
2,3; moderate



3; low - moderate
Uncommon




Uncommon
Increased trafficking, cultivation, overgrazing, export of organic matter

As for sheet and rill
erosion above
-




Increased ponding of water in low-lying areas
Increased soil disruptionIncreased soil break-upGully erosion3 ; low - moderateUncommonAs for sheet and rill erosion aboveIncreased sediment load and turbidity of streams.
Comments: -
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