Mitchell (Ml)

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

Area: 65 sq. km (0.4%)

Some of the valleys in areas with ridge-and-ravine topography are flanked by low spurs and small terrace remnants well above the modern flood plain. The spurs are probably remnants of an earlier, wider valley floor dissected during a phase of more active stream downcutting. The slope gradients, parent rocks, soils and vegetation of these erosional spurs are very similar to those of adjacent lands but the crests tend to be rounded. These spurs and terrace remnants now mainly form meander cores and are mapped in Mitchell land system. Modern flood plains, narrower than those in Walnut land system, are also included, as are some colluvial slopes.

On the sedimentary rocks the soils are similar to those on adjacent lands, tending to be shallow, light-textured, yellow or brown coloured, acidic, structureless in the subsoil and stony. On more stable, gentler slopes, the clay content may increase gradually with depth. The remnants of ancient alluvium are likely to have yellowish brown duplex or gradational soils containing much quartz gravel. The modern alluvial deposits have little soil development other than organic matter accumulation and crumb structure formation in the topsoil and the development of reddish or brownish earthy subsoils.

The dominant vegetation is open forest II, mainly shrubby, with some grassy open forest II or III on the modern alluvial terraces and fringing major stream channels.

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

Open forest growing along the Timbarra River somewhat covers the break in slope between the low spurs and relict terraces, diagnostic features of Mitchell land system, and the steep slopes of Carrabungla land system.

CLIMATE Rainfall, mean (mm) Temperature, mean (°C) Seasonal growth limitations	Annual 600 - 900; lowest July or August (30 - 50), highest October (50 - 80) Annual 12 - 14; lowest July (8 - 10), highest February (19 - 21) Temperature <10°C (av.): May - September Rainfall < potential evapotranspiration: November – March
GEOLOGY Age, lithology	Mainly Ordovician sandstones, siltstones and shales; minor Carboniferous Sediments and Devonian rhyodacites and rhyolites; Holocene sandy alluvium
PHYSIOGRAPHY Landscape Elevation range (m) Relative relief (m) Drainage pattern Drainage density (km/km²)	Broad valleys with narrow or discontinuous flood plains flanked by low erosional spurs 120 - 440 20 - 100 Dendritic 3.1
PRESENT LAND USE	Mostly uncleared: hardwood forestry (minor timber products); apiculture Minor proportion cleared: grazing of sheep and cattle

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

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

LAND COMPONENT Percentage of land system Diagnostic features	1 65 Spurs. rocky rises and high terrace remnants, mostly meander cores	2 15 Lower slopes	3 15 Terraces	₄ 5 Major stream channels
PHYSIOGRAPHY Slope %, typical and (range) Slope shape	15 - 25, (0 - 40) Convex	10 - 20, (5 - 25) Concave	2, (0 - 5) Straight but uneven	<1, (0 - 5) Concave
SOIL
Parent material	Sandstone, siltstone, shale; minor ancient alluvium	Coarse and medium textured colluvium	Mainly coarse textured alluvium	-
Description	Limited observations — soil probably mainly similar to that in adjacent land systems, ie. Talbotville 1: Turton 1,2 and Carrabungla 1.2; rarely duplex	Limited observations — probably dark greyish brown sandy to loamy topsoil gradually becoming yellower or browner and more clayey with depth; may be gravelly	Younger terraces: undifferentiated grey or brown sandy loam over stratified alluvium. Older terraces: brown or reddish earthy sandy loam	No soils, only moving alluvial deposits: sand and gravel bedload
Classification	Mostly Brown and Yellow Earths, also Lithosols Uc4. - . Uc5. - , Um5. - . Gn2. -	Brown and Yellow Earths Gn2.44	Alluvial Soils, some Red Earths Ucl.21, Gn2.01, Uc5.21	-
Surface texture	Sandy loam to clay loam	Sandy loam to clay loam	Sand to sandy loam	-
Surface consistence	Friable when moist	Friable when moist	Loose to friable when moist	-
Depth (m)	Mostly <0.8	>2.0	>2_.0	-
Nutrient status	Low	Low to moderate	Low	-
Available soil water capacity	Low to moderate	Moderate	Low to moderate	-
Perviousness to water	Moderate	Moderate	Rapid	-
Drainage	Good	Probably very variable	Good	-
Exposed stone (%)	0 - 60	0 - 20	0	-
Sampled profile number	-	-	-	-
NATIVE VEGETATION Structure of vegetation and characteristic species of dominant stratum (+ Predominant species)	Open forest II, sometimes shrubby: Limited data — probably mixed species forests with E. goniocalyx or E. dives predominant. Associated species include E. polyanthemos and E. radiata	Open forest II. sometimes shrubby: E. radiata+ and/or E. stellulata+. Associated species include E. ovata, E. viminalis	Shrubby or grassy open forest II. III: Predominant species variable. usually one or more of E. melliodora, E. viminalis, E. radiata, E. polyanthemos; E. cypellocarpa sometimes associated	Fringing vegetation of shrubby or grassy open forest II, III: Species as in component 3

Disturbance	Affected process and trend	Primary resultant deterioration			Casual activities	Primary off-site process
Disturbance	Affected process and trend	Form	Susceptibility of components	Incidence with components	Casual activities	Primary off-site process
Alteration of vegetation: — reduction in leaf area, rooting depth and/or perenniality	Reduced transpiration, resulting in increased deep percolation	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	12; moderate 3; low	Not determined	Clearing, logging, burning, road building and other earth-moving activities, 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 1,2; moderate 3; low	Not determined Not determined	Increased trafficking 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	1,2; moderate 3; high 4: high	Not determined Not determined Not determined	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 Increased sediment load and turbidity Increased sediment load and turbidity
Comments: No observations of deterioration

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