Wonnangatta (Wa)

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

Area: 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 <10°C (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 USE	Mostly 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- cs

A 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
Disturbance	Affected process and trend	Form	Susceptibility of components	Incidence within components	Causal activities	Primary off-site process
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 soil	Increased overland flow and soil detachment	Sheet and rill erosion	1; moderate - high 2; moderate	Common	Clearing, 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 soil	Increased 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 disruption	Increased soil break-up	Gully 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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