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Wonnangatta (Wa)

A study of the land in the Catchment of Gippsland Lakes - Vol 2 - land system Wonnangatta- geoArea: 1008 sq. km (5.0%)

This extensive land system occurs on the hilly terrain with Ordovician, Devonian and Silurian sediments in the central and eastern parts of the East Victorian Uplands. The prominent ridge-and-ravine topography is characterised by moderately long, steep slopes, rock outcrop and active soil creep. Levees and alluvial flats similar to, though smaller than, those mapped in Walnut land system, occur occasionally along a few major streams, notably the Nicholson and Wonnangatta rivers. In most respects, Wonnangatta is a lower-relief version of Talbotville land system. It is similar in geology and topography to La Trobe land system but the climate is much drier.

Steep slopes, slow-weathering sedimentary rocks and a climate which is inadequate to support vigorous and dense vegetation give rise to relatively rapid rates of natural erosion and slow soil formation. Thus shallow, stony, leached and acidic soils are characteristic. The structure of the topsoils tends to be weakly developed and subsoils are often apedal. Removal of the vegetation is likely to lead to severe sheet erosion.

Shrubby open forest II predominates, with open forest III on protected sites and in some drainage corridors.
A study of the land in the Catchment of Gippsland Lakes - Vol 2 - land system Wonnangatta- image
Hills with ridge-and-ravine topography and moderately long steep slopes north of Glenmaggie

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

Annual 700 - 1200; lowest January or February (40 - 80), highest October (100 - 150)

Annual 8 - 12; lowest July (3 - 7), highest February (16 - 20)
Temperature <10C (av.): April - October
Rainfall < potential evapotranspiration: December - February; occasional winter snow
GEOLOGY
Age, lithology

Ordovician, Silurian and Devonian sandstones, siltstones and shales
PHYSIOGRAPHY
Landscape
Elevation range (m)
Relative relief (m)
Drainage pattern
Drainage density (km/km2)

Steep hills with ridge-and-ravine topography

80 - 520
60 - 300
Dendritic
1.6
PRESENT LAND USEMostly uncleared: hardwood forestry (minor timber products); apiculture; bush grazing of cattle (limited); small areas in Fairy Dell Scenic Reserve
Minor proportion cleared: grazing of beef cattle and sheep

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

LAND COMPONENT
Percentage of land system
Diagnostic features
1
70
Exposed slopes, drier forest
2
25
Protected slopes, moister forest
3
5
Isolated narrow terraces in
drainage corridors
PHYSIOGRAPHY
Slope %, typical and (range)
Slope shape
25 - 30, (15 - 60)
Straight
25 - 30, (15 - 60)
Straight
Variable, (0 - 30)
Straight but uneven
SOIL
Parent material
Mudstone, siltstone, sandstone and shale
Alluvium
Description
Dark clay loam to sandy loam grading into similarly or heavier textured brown or reddish brown subsoil. Shallow to very shallow, stony and acidic, but tending to be deeper in component 2
Little differentiated greyish brown loamy sand to clay loam
Classification
Lithosols; some Brown Earths and Red Podzolic Soils; Wiesenboden in small seepage areas
Um4.13, Um5.51, Uc4.32, Uc1.44, Gn2.41, Gn4.34, Dr3.21, Dr3.61
Alluvial Soils
Uc1.43, Uc1.44, Um5.52
Surface texture
Clay loam to sandy loam
Loamy sand to clay loam
Surface consistence
Slightly hard when dry, friable when moist
Varies with texture
Depth (m)
Commonly <0.7, deeper pockets
>2.0
Nutrient status
Low
Low
Available soil water capacity
Low to moderate
Low to moderate
Perviousness to water
Moderate
Moderate to rapid
Drainage
Good
Varies from somewhat poor to good
Exposed stone (%)
5 - 80
0
Sampled profile number
-
-
NATIVE VEGETATION
Structure of vegetation and
characteristic species of
dominant stratum
(+ Predominant species)
Mainly shrubby open forest II, occasionally grassy open woodland: Mixed forests including — E. sieberi, E. macrorhyncha, E. goniocalyx, E. dives, E. globoidea (one of these usually predominant), E. polyanthemos, E. radiata, E. cypellocarpa, E. sideroxylon
Shrubby open forest III: E. muellerana+ or E. obliqua+ or, on upper slopes, E. sieberi+; E. cypellocarpa, E. globulus, E. sideroxylon commonly associated
Occasionally closed forest II of Acmena smithii, climbers, ferns and epiphytes in drainage gullies
Mainly shrubby open forest II, III: E. bridgesiana+ and/or E. viminalis+, sometimes with E. radiata Rarely closed forest II: Acmena smithii, climbers, ferns and epiphytes

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




— reduction in density of tree roots
Reduced transpiration,
resulting in:

a) increased deep
percolation




b) increased regolith
wetness


Decreased root-binding




Nutrient loss




Soil creep



Soil creep




Not determined




1; moderate
2; moderate – high


1; moderate
2; moderate - high




Not determined




Common: on steep slopes


Common: on steep slopes




Removal of trees




Accelerated by major disturbance of native vegetation

Accelerated by major disturbance of native vegetation




Increased movement of water to groundwater; increased base-flow of streams

Increased sediment load

Increased sediment load

Increased exposure of surface soilIncreased overland flow and soil detachmentSheet and rill erosion1; moderate - high
2; moderate
CommonClearing, logging, burning, overgrazing, road and dam building and other earth-moving activities, trafficking by stock.Increased flash flows and sediment load.
Increased physical pressure on soilIncreased compaction

With


Reduced infiltration
Structure decline




Sheet and rill erosion
1; low
2; moderate



1; moderate - high
2; moderate
Uncommon




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

As for sheet and rill
erosion above
-




Increased flash flows
Increased soil disruptionIncreased soil break-upGully erosion



Tunnel erosion


Streambank erosion
1,2; moderate



1; moderate on colluvial
slopes

3; high
Common: locally severe


Common


Uncommon
As for sheet and rill erosion above


As for sheet and rill erosion above

As for sheet and rill erosion above
Increased sediment load and turbidity of streams.

Increased sediment load and turbidity of streams.

Increased sediment load and turbidity of streams.
Comments: Severe tunnel erosion occurs near Lake Glenmaggie
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