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Mitchell (Ml)

A study of the land in the Catchment of Gippsland Lakes - Vol 2 - land system Mitchell- geoArea: 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 <10C (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 USEMostly 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- csA 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
Form
Susceptibility of components
Incidence with components
    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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