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Delburn (Dl)

A study of the land in the Catchment of Gippsland Lakes - Vol 2 - land system Delburn- geoArea: 46 sq. km (0.2%)

In the South Victorian Uplands, erosion has removed most of the Tertiary sediments and associated, weathered products overlying the Older Volcanics. Some areas however, still retain part of the weathered kaolinized, basaltic regolith and these have been mapped in Delburn land system. They occur mainly in the western part of the Morwell River Catchment.

Topography consists of hills and long slopes with a broad. dendritic-dissection pattern. The areas of elevated volcanics from which erosion has removed most or all of the kaolinized regolith, are mapped as Neerim and Thorpdale land systems.

A study of the land in the Catchment of Gippsland Lakes - Vol 2 - land system Delburn- image
Deep soils mantle the gentle slopes of Delburn land system; grazing is the main land use
Basaltic rocks weather to clays and silts and where these are kaolinized much of the original iron content has been removed. Consequently the soils on this kaolinized basalt are predominantly pale brown or yellowish brown and clayey with a medium blocky structure. They contrast with the finely-structured, bright-reddish-brown soils that have developed on the less-weathered basalt in Neerim and Thorpdale land systems. The soils in Delburn are also leached, acidic and generally gradational, though there is a tendency towards a more developed, duplex profile on the gentler slopes of component 2.

Most of the native vegetation, probably mainly open forest II with more shrubby understories in valley floors, has been cleared.

CLIMATE
Rainfall, mean (mm)
Temperature, mean (C)
Seasonal growth limitations

Annual 700) - 1200; lowest January or February (40 - 70), highest August or October (90 - 120)

Annual 12 - 14; lowest July (8 - L0), highest February (19 - 21)
Temperature <10C' (av.): May - September
Rainfall < potential evapotranspiration: November – March
GEOLOGY
Age, lithology

Tertiary basalts (Older Volcanics), highly and deeply weathered
PHYSIOGRAPHY
Landscape
Elevation range (m)
Relative relief (m)
Drainage pattern
Drainage density (km/km2)

Long slopes and hills with a broad dissection pattern

40 - 260
20 - L40
Dendritic
0.9
PRESENT LAND USEMostly cleared: softwood forestry: some grazing of beef and dairy cattle on improved pastures
Minor proportion uncleared: hardwood forestry (minor timber products with some general construction timber); apiculture

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

LAND COMPONENT
Percentage of land system
Diagnostic features
1
40
Crests and upper slopes
2
30
Gentle to moderate slopes with
pale kaolinitic soil
3
20
Protected shorter slopes with
deeper reddish soils
4
10
Drainage depressions,
often swampy
PHYSIOGRAPHY
Slope %, typical and (range)
Slope shape
5 - 10, (0 - 20)
Convex
5 - 10. (5 - 30)
Straight tending concave
15, (5 - 30)
Straight tending convex
2, (0 - 5)
Concave
SOIL
Parent material
Weathered, mostly kaolinised basalt
Mainly fine-textured alluvium
Description
Brown loam to clay loam merging into slightly reddish brown or yellowish brown blocky clay subsoil
Brown sandy clay loam to clay loam merging into pale brown or brownish yellow blocky clay subsoil
Dark greyish brown to dark reddish brown loam to clay loam merging into reddish brown or brown blocky clay subsoil
Limited observations — probably mainly dark silty clay loam over strongly mottled yellowish brown clay subsoil
Classification
Xanthozems, Yellow Podzolic Soils
Gn3.91, Gn4.31, Gn4.51, Gn4.81, Dy3.41
Yellow Podzolic Soils. Xanthozems
Dy3.11, Dy3.21, Gn3.71
Krasnozems. Brown Earths
Gn3.11. Gn3.52. Gn4.11. Gn4.51
Probably Wiesenboden, Humic
Gleys
-
Surface texture
Loam to clay loam
Sandy clay loam to clay loam
Loam to clay loam
-
Surface consistence
Friable when moist
Friable when moist
Friable when moist
Friable when moist
Depth (m)
1.5 –2.0
1.5 - 2.0
1.0 - >2.0
>2.0
Nutrient status
Low to moderate
Low to moderate
Low to moderate
Low to moderate
Available soil water capacity
Moderate
Moderate
Moderate
Moderate to high
Perviousness to water
Moderate to rapid
Moderate to rapid
Moderate to rapid
Slow to moderate
Drainage
Good
Moderately good
Good
Poor
Exposed stone (%)
0
0
0
0
Sampled profile number
-
-
-
-
NATIVE VEGETATION
Structure of vegetation and
characteristic species of
dominant stratum
(+ Predominant species)
Open forest II:
Mixed forests with predominant species and composition variable
including E. obliqua (usually predominant), E. cypellocarpa,
E. radiata, E. sieberi (mostly on crests) and E. viminalis
Open forest II, III:
Mixed forests with predominant
species and composition variable
— as for components 1 and 2
Shrubby open forest II:
E. ovata+ with or without E. radiata+

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 and leaching
    Nutrient loss
    1.2,3; low
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
    1.2,3; moderate
Not determined
    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
    L.2.3; moderate
    4: high


    1,2,3: moderate
Not determined



Not determined
    Loss of organic matter from topsoil


    As for sheet and rill
    erosion above
    -



    Increased flash flows
    Increased soil disruption
    Increased soil break-up
    Gully erosion
    1.2; moderate
    3; low
Not determined
    As for sheet and rill
    erosion above
    Increased sediment load.
    Comments: -
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