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Gunyah (Gh)

A study of the land in the Catchment of Gippsland Lakes - Vol 2 - land system Gunyah- geoArea: 112 sq. km (0.6%)

Hills with ridge-and-ravine topography and moderately long, steep slopes on Cretaceous mudstones, siltstones and sandstones in the South Victorian Uplands are mapped in Gunyah land system. Most occurrences are on the lower parts of the uplifted Balook Block. Landslides have been an important slope process, probably because of the soft porous nature of the sediments and the history of tectonic activity. This land system is similar to Jeeralang in most respects but has lower relief and elevation, and shorter slopes.

A somewhat cool, humid environment, a sedimentary rock that weathers relatively easily and mostly steep slopes, have resulted in uniform and gradational soils with loam to light clay textures. The soils tend to have a medium to fine blocky structure and roots readily penetrate the subsoil horizons. Nutrient status is probably higher than that on most sedimentary rocks in the study area.

The vegetation is mainly E. regnans layered open forest III, with open forest II and III on more exposed aspects or where rainfall is lower.
A study of the land in the Catchment of Gippsland Lakes - Vol 2 - land system Gunyah- image
Regenerating forest allows the ridge-and-ravine topography to be clearly visible.

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

Annual 900 - 1600; lowest January (60 - 90), highest August or October (120 - 150)

Annual 8 - 12, lowest July (3 - 7), highest February (16 - 20)
Temperature <10C (av.): May - September
Rainfall < potential evapotranspiration: December - February; occasional winter snow
GEOLOGY
Age, lithology

Cretaceous sandstones, mudstones, siltstones and conglomerates of the Strzelecki Group
PHYSIOGRAPHY
Landscape
Elevation range (m)
Relative relief (m)
Drainage pattern
Drainage density (km/km2)

Steep hills with ridge-and-ravine topography

60 - 500
80 - 200
Dendritic
1.8
PRESENT LAND USEMostly uncleared: hardwood forestry; bush grazing of cattle (limited)
Minor proportion cleared: grazing of beef and dairy cattle on improved pastures; softwood plantations

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

LAND COMPONENT
Percentage of land system
Diagnostic features
1
65
Steep slopes, with old
landslide scars common, and
narrow rounded crests
2
15
Less steep lower slopes,
often poorly drained
3
10
Broader rounded ridge
crests, mostly at lower
elevations
4
5
Steeper slopes of
gullies and ravines
5
5
Small flats within
major drainage corridors
PHYSIOGRAPHY
Slope %, typical and (range)
Slope shape
35 - 40, (30 - 60)
Straight
15 - 25, (5 - 30)
Straight
5 - 10, (0 - 15)
Convex
Variable, (5 - 20)
Straight
2, (0 - 5)
Straight
SOIL
Parent materialMudstone, siltstone and sandstone
Description
Dark greyish brown loam
to light clay merging into
brown to yellowish brown
medium clay
Mostly as for component1; some duplex profilesNo observations — shallow brown soil on steep slopes; humic wet soil in ravine bottomsLocally derived alluvium Brown sandy loam to sandy clay loam, commonly clay at depth
Classification
Brown Earths
Uf6.11, Gn3.21, Gn4.71, Gn4.51
Brown Earths, Grey-brown Podzolic Soils
Uf6.13, Gn3.91, Gn4.31, Gn4.51, Dy3.21
-
-
Alluvial Soils
Um5.52, Gn4.51
Surface textureLoam to light clayLoam to light clayLoam to clay loamSandy loam to sandy clay loam
Surface consistenceHardHardVariableSlightly hard
Depth (m)1.0 - 2.01.0 -2.0Variable>2.0
Nutrient statusModerateModerateModerateModerate
Available soil water capacityModerateModerateModerateModerate
Perviousness to waterModerate to rapidModerate to rapidModerate to rapidModerate to rapid
DrainageGoodModerately good to goodVariableVariable
Exposed stone (%)0000
Sampled profile number14, 34---
NATIVE VEGETATION
Structure of vegetation and
characteristic species of
dominant stratum
(+ Predominant species)
Protected aspects or where rainfall <1100 mm, layered open forest III:
E. regnans+

More exposed aspects, or where rainfall >1100 mm, open forest II, III:
E. obliqua+, E. globulus+, E. cypellocarpa
Layered open forest III with ferns:
E. regnans+, Dicksonia antarctica, Alsophilaaustralis
Shrubby open forest III, IV:
E. viminalis+ with or without E. regnans+

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


    — reduction in density of tree roots
    Reduced transpiration,
    resulting in:

    a) increased deep percolation and leaching



    b) increased regolith wetness


    Decreased root-binding



    Nutrient loss




    Soil creep



    Soil creep



    Not determined




    1,4; high
    2; moderate


    1,4; high
    2; moderate



    Not determined




    Common: visible on cleared land


    Common: visible on cleared land



    Removal of trees




    Accelerated by clearing major disturbance of the native vegetation

    Accelerated by clearing major disturbance of the native vegetation



    Increased movement of water to groundwater; increased base-flow of streams

    Increased sediment load



    Increased sediment load

    Increased exposure of surface soil
    Increased overland flow and soil detachment
    Sheet and rill erosion
    1,2,4; high
    3; moderate
    Common
    Cultivating, logging, burning, road building and other earth-moving activities, trafficking by stock.
    Increased flash flows and sediment load.
    Increased physical pressure on soil
    Increased compaction

    with


    Reduced infiltration
    Structure decline


    Sheet and rill erosion
    12,3,4; high
    5; moderate


    1,2,4; high
    3; moderate
    Uncommon



    Common
    Increased trafficking 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


    Streambank erosion
    1; high
    2,3; moderate

    5; high
    Uncommon: local occurrence

    Uncommon
    As for sheet and rill erosion above

    As for sheet and rill erosion above
    Increased sediment load.


    Increased sediment load and turbidity of streams
    Comments: Regeneration of vegetative cover is quite rapid because of good growing conditions
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