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Nambrok (Nk)

A study of the land in the Catchment of Gippsland Lakes - Vol 2 - land system Nambrok- geoArea: 32 sq. km (0.2%)

Parts of the later Pleistocene terrace which are periodically inundated are mapped in Nambrok land system and occur where drainage is poor and run-off water accumulates, notably to the north of Snake Ridge between Sale and Rosedale. Waterlogging after rainfall has given rise to hydromorphic, locally-saline soils. In recent years irrigation of adjoining land has caused water tables to rise, aggravating the salinity and drainage problems. Artificial drainage installed in many areas, has largely alleviated these problems.

The youthful clayey soils have clay loam to silty clay loam topsoils which gradually merge into clays with depth. Subsoils are always mottled, although the depth at which mottling begins and its intensity are not uniform and probably depend on drainage status. The more poorly-drained areas have rusty coloured fine mottles in the topsoils, particularly along root channels. The main soil degradation hazards are increased waterlogging and salinity due to irrigation and clearing of native vegetation higher in the catchment. The salinity hazard is judged to be high.

The native vegetation, probably dominated by a grassy open forest II of E. tereticornis, has been almost entirely cleared.
A study of the land in the Catchment of Gippsland Lakes - Vol 2 - land system Nambrok- image
Surface water and pugging of the surface soil by cattle are indicative of the poor drainage of this land system

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

    Annual 500 - 800; lowest July (30 - 50), highest October (50 - 80)

    Annual 12 - 14; lowest July (8 - 10), highest February (19 - 21)
    Temperature <10C (av.): June - August
    Rainfall < potential evapotranspiration: November – March
GEOLOGY
Age, lithology
PHYSIOGRAPHY
Landscape
Elevation range (m)
Relative relief (m)
Drainage pattern
Drainage density (km/km2)

    Poorly-drained, alluvial plains and shallow depressions

    20 - 40
    0 - 1
    Dendritic
    1.5
PRESENT LAND USE
    Cleared: grazing of beef and dairy cattle on improved, often irrigated pastures; some apiculture

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

LAND COMPONENT
Percentage of land system
Diagnostic features
1
80
Low-lying, poorly drained plains
2
20
Depressions and channels on poorly drained plains
PHYSIOGRAPHY
Slope %, typical and (range)
Slope shape
<1, (0 - 1)
Straight or slightly concave
<1, (0 - 1)
Concave
SOIL
Parent material
Alluvial silt and clay
Description
Dark brown to dark greyish brown clay loam or silty clay loam grading
into dark yellowish brown, often strongly mottled blocky structured
clay subsoil; topsoil mildly acidic, subsoil neutral to alkaline. Low
rises with less subsoil mottling
Grey clay loam to silty clay loam with few to many fine yellowish brown
mottles, grading into grey and yellowish brown mottled clay subsoil.
Surface usually mildly acidic, alkaline at depth
Classification
Wiesenboden; some Minimal Prairie Soils on better drained low rises
Gn3.93, Gn4.33, Gn4.72
Humic Gleys
Uf6.41, Gn3.43
Surface texture
Clay loam to silty clay loam
Clay loam to silty clay loam
Surface consistence
Friable when moist
Friable to firm when moist
Depth (m)
>2.0
Nutrient status
Moderate
Available soil water capacity
Moderate to high
Perviousness to water
Slow
Drainage
Poor to somewhat poor
Very poor to poor
Exposed stone (%)
0
0
Sampled profile number
-
28
NATIVE VEGETATION
Structure of vegetation and
characteristic species of
dominant stratum
(+ Predominant species)
Grassy open forest II: E. tereticornis+
Clearing has made it difficult to determine other tree species which may have grown in association

    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 saline groundwater table
    Salting and waterlogging
    1; moderate
    2; high
    Common
    Reduce plant-water use in the catchment
    Raised watertables
    Increased physical pressure on soil
    Increased compaction

    With


    Reduced infiltration
    Structure decline




    Waterlogging
    1; high
    2; moderate – high



    1; moderate
    2; high
    Uncommon




    Common
    Increased trafficking and cultivation, overgrazing, export of organic matter


    As for structure decline
    above
    -




    Increased ponding of water in lower areas
    Comments: The land surface has become waterlogged and salt-affected since settlement, particularly in the lower-lying component 2; aggravated by irrigation, however the installation of drains has alleviated the problem. Salting has been observed just to the north west of Kilmany.
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