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Trafalgar (Tr)

A study of the land in the Catchment of Gippsland Lakes - Vol 2 - land system Trafalgar- geoArea: 65 sq. km (0.4%)

Alluvial and colluvial outwash material from the South Victorian Uplands has accumulated in a broad apron in the area between Yarragon and Moe and the area is mapped as the Trafalgar land system. The clayey colluvium was derived mainly from soft, Cretaceous sediments and basic volcanics following uplift of the South Victorian Uplands. Surface drainage is often poor but ochreous colours in deeper layers indicate better drainage at depth. Surface wash still occurs but active colluviation now appears to be minimal. The boundary with the Moe land system is indistinct at the more distal parts.

The soils have formed mainly on fine-textured colluvium and alluvium under conditions of seasonal wetness, especially in the low-lying areas receiving run-off and seepage water from adjacent hills. The soils of the higher, more-steeply-sloping areas may dry out completely during summer.

A study of the land in the Catchment of Gippsland Lakes - Vol 2 - land system Trafalgar- image
The almost flat distal parts of a colluvial apron below the lower slopes of the Strzelecki Ranges from which the material was derived. The more sloping, proximal parts of the apron are just visible.
Mottling is strong in most subsoils and may extend to the surface in places. Moderate nutrient levels are inherited from the source sediments. Erosion hazards are slight but the soils are susceptible to structure decline caused by trafficking and trampling, particularly when wet.

The original vegetation, probably dominated by open forest II or III of E. ovata, has been almost entirely 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 - 10), highest February (19 - 21)
Temperature <10C (av.): June - August
Rainfall < potential evapotranspiration: November – March
GEOLOGY
Age, lithology

Pleistocene Holocene silty and clayey colluvium and alluvium derived from Cretaceous sediments and Tertiary volcanics
PHYSIOGRAPHY
Landscape
Elevation range (m)
Relative relief (m)
Drainage pattern
Drainage density (km/km2)

Low-angle outwash fans and aprons

60 - 800
0 - 5
Dendritic
0.8
PRESENT LAND USECleared: grazing of beef and dairy cattle on improved pasture; some apiculture

LAND COMPONENT
Percentage of land system
Diagnostic features
1
50
Sloping proximal parts of fans and aprons
2
40
Almost flat distal parts of fans and aprons
3
10
Shallow drainage depressions
PHYSIOGRAPHY
Slope %, typical and (range)
Slope shape
2, (0 - 5)
Concave
<1, (0 - 2)
Straight to slightly concave
<2, (0 - 2)
Concave
SOIL
Parent material
Silty and clayey colluvium and alluvium
Description
Limited observations — probably mainly very dark greyish brown sandy clay loam to light clay topsoil merging into greyish brown strongly mottled subsoil with texture ranging from silty loam to heavy clay; stratified colluvium or alluvium below. Waterlogging during winter and spring common in components 1 and 2
Classification
Wiesenboden; possibly Humic Gleys in component 3
Gn2.81, Gn4.51, Um2.31
Surface texture
Sandy clay loam to light clay
Surface consistence
Friable to firm when moist
Depth (m)
>2.0
Nutrient status
Moderate
Available soil water capacity
Moderate
Perviousness to water
Slow
Drainage
Somewhat poor
Poor to somewhat poor
Very poor
Exposed stone (%)
0
0
0
Sampled profile number
43
-
-
NATIVE VEGETATION
Structure of vegetation and
characteristic species of
dominant stratum
(+ Predominant species)
Open forest II:
E. ovata +
Understorey often includes Melaleuca ericifolia or M. squarrosa
Clearing has made it difficult to determine other predominant or associated tree species

    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 raised watertables
    Waterlogging
    1; moderate
    2,3; high
    Common: in low-lying areas
    Reduced plant water-use in the catchment
    Increased run-on and ponding in low-lying areas
    Increased exposure of surface soil
    Increased overland flow and soil detachment
    Sheet and rill erosion
    1; low
    2; very low
    Uncommon
    Overgrazing, cultivating, road and dam 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
    12,3; low – moderate



    1; low
    2; very low
    Uncommon



    Uncommon
    Increased trafficking, cultivation, overgrazing, export of organic matter

    As for sheet and rill erosion above
    -



    Increased ponding in low-lying areas
    Increased soil disruption
    Increased soil break-up
    Gully erosion
    1,3; low - moderate
    2; very low
    Uncommon
    As for sheet and rill erosion above
    Increased sediment load.
    Comments: -
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