Avon (Av)

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

Area: 247 sq. km (1.2%)

Low hills and gentle slopes occur on Carboniferous sediments at relatively low elevations close to the southern margin of the East Victorian Uplands and along some of the major river valleys. These areas are mapped in Avon land system. Ridge crests are generally rounded and slopes are short. Structural control of slope gradient and shape is often evident and some rock outcrop occurs on crests and ledges. Red-bed shales can sometimes be observed in road cuttings. Avon is similar to Glenmaggie land system but has lower relief and gentler slopes.

Rocks, which weather to clays, silts and sands on relatively gentle slopes with moderate rainfall, enhance the formation of duplex soils. The alkaline nature of some subsoils may increase the risk of gully erosion.

The vegetation is mainly shrubby open forest II, with some open forest III on protected hillslopes and valley floors. Scattered pockets of closed forest II occur in narrow, steep-sided gullies.

A study of the land in the Catchment of Gippsland Lakes - Vol 2 - land system Avon - image

A shrubby open forest, with leaf litter forming a relatively large proportion of the ground cover, typical of this land system.

CLIMATE Rainfall, mean (mm) Temperature, mean (°C) Seasonal growth limitations	Annual 600 - 900; lowest July (40 - 70), highest October (60 - 90) Annual 12 - 14; lowest July (8 - 10), highest February (19 - 21) Temperature <10°C (av.): May - September Rainfall < potential evapotranspiration: December – February
GEOLOGY Age, lithology	Lower Carboniferous freshwater siltstones, minor sandstones, conglomerates, often red (Snowy Plains Formation) with alternating quartzose and feldspathic sandstones and 'red-bed' siltstones
PHYSIOGRAPHY Landscape Elevation range (m) Relative relief (m) Drainage pattern Drainage density (km/km²)	Low rounded hills and undulating terrain 60 - 520 20 - 140 Dendritic 0.7
PRESENT LAND USE	Mostly uncleared: hardwood forestry (minor timber products); apiculture; bush grazing (limited); small area in Glenaladale National Park Minor proportion cleared: grazing of beef cattle and sheep

A study of the land in the Catchment of Gippsland Lakes - Vol 2 - land system Avon - cs

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

LAND COMPONENT Percentage of land system Diagnostic features	1 40 Exposed slopes and narrow, often rocky crests	2 30 Broad, often gently undulating crests	3 20 Protected slopes	4 5 Flats in major drainage corridors	5 5 Fans and associated minor drainage depressions
PHYSIOGRAPHY Slope %, typical and (range) Slope shape	15-20,(10-50) Straight or concave	5-10,(0-20) Convex	15-20,(10-50) Concave	2.(0-5) Straight but uneven	2 - 5.(0-10) Straight
SOIL Parent material	Siltstone, quartzose and feldspathic sandstone; some conglomerate			Alluvium of variable texture	Colluvium and local alluvium
Description	Dark greyish brown, dark grey or dark brown sandy loam to clay loam topsoil abruptly overlying yellowish brown or reddish brown clay subsoil, mostly acidic and whole coloured; subsoils sometimes alkaline. Brown or greyish brown uniform loamy sand, in places shallow on or near quartzose sandstone.			Limited observations – mainly undifferentiated brown sand and loam	Duplex with yellowish brown mottled clay subsoil (on colluvium) and brown loam (on colluvium)
Classification	Yellow and Red Podzolic Soils, Solodic Soils, some Earthy Sands Dy2.21, Dy2.33, Dy3.43, Dy3.61, Dr2.11, Dr2.21, Dr3.21, Uc4.13, Uc4.24			Alluvial Soils Uc1.24	Yellow Podzolic Soils Dy2.22, Um1.44
Surface texture	Sandy loams (mainly) to clay loams			-	Sandy loams to clay loams
Surface consistence	Variable: soft to hard when dry, friable to firm when moist			-	Variable
Depth (m)	Variable: 0.8-1.5			>2.0	>2.0
Nutrient status	Low to moderate			Low to moderate	Low to moderate
Available soil water capacity	Low (sandy soils) to moderate			Low to moderate	Low to moderate
Perviousness to water	Slow to moderate			Moderate to rapid	Slow to moderate
Drainage	Mainly good			-	Very poor to somewhat poor
Exposed stone (%)	<10			0	0
Sampled profile number	-	56	-	-	-
NATIVE VEGETATION Structure of vegetation and characteristic species of dominant stratum (+ Predominant species)	Open forest I. II. Often shrubby: E. macrorhyncha+. E. polyanthemos+, E. tereticornis+ or E. sieberi+; and E. baxteri often	Open forest II: E. melliodora+, E. cypellocarpa associated	Open forest II, III, often shrubby: Composition variable — E. cypellocarpa, E. globoidea, E. sieberi or E. tereticornis usually predominant; E. muellerana, E. sideroxylon and E. baxteri associated	Limited data — probably mainly open forest II, III, often shrubby of E. melliodora+, E. viminalis+ or E. radiata+ Rarely closed forest II of Acmena smithii, climbers, ferns and epiphytes	Mostly open forest II with composition variable and Including, E. bridgesiana. E. radiata,, E. viminalis Occasionally closed scrub of Melaleuca ericifolia or closed forest as for component 4

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	Reduced transpiration, resulting in increased deep percolation and leaching	Nutrient loss	Not determined	Not determined	Removal of trees	Increased movement of water to groundwater; increased base-flow of streams
Increased exposure of surface soil	Increased overland flow and soil detachment	Sheet and rill erosion	1,3; moderate 2; low	Uncommon	Clearing, logging, burning, overgrazing, road and dam building and other earth-moving activities, rabbit burrowing, 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	1,2,3; low - moderate 4; low 5; moderate 1,3: moderate 2; low	Uncommon Uncommon	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 Scour erosion Streambank erosion	1,3,5; moderate 2; low 4; moderate 4; high	Uncommon Uncommon 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. Increased sediment load Increased sediments load and turbidity
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