Yinnar (Yr)

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

Area: 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 <10°C (av.): June - August Rainfall < potential evapotranspiration: November – March
GEOLOGY Age, lithology	Lower Pleistocene alluvium of sands, silts and clays
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- cs

A 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 drainag^e 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 Podzoli^c 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
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 a raised watertable	Waterlogging	1,4; low 2; moderate	Common; in low-lying areas	Reduced plant water-use in the catchment	Increased movement of water to groundwater and raised watertables
Increased exposure of surface soil	Increased overland flow and soil detachment	Sheet and rill erosion	3; low - moderate	Uncommon	Clearing, 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 soil	Increased 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 disruption	Increased soil break-up	Gully erosion	3 ; low - moderate	Uncommon	As for sheet and rill erosion above	Increased sediment load and turbidity of streams.
Comments: -

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