Nambrok (Nk)

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

Area: 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 <10°C (av.): June - August Rainfall < potential evapotranspiration: November – March
GEOLOGY Age, lithology	Upper Pleistocene alluvial silts and clays
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- cs

A 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_drainedplains
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
Disturbance	Affected process and trend	Form	Susceptibility of components	Incidence with components	Casual activities	Primary off-site process
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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