Rotamah (Rh)

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

Area: 14 sq. km (0.1%)

Rotamah land system occurs near Lakes Entrance on Holocene sands added to the inner barrier; these sands are adjacent to the modern coastal foredune system. As with the rest of the inner barrier which is of older sands, an uneven sand sheet has formed from a close sequence of beach-ridge deposits. There is also a slightly different vegetation type, probably resulting from the slightly more humid climate.

Although the marine sands originally contained shell fragments, the carbonate has been removed by leaching. The sands are now acidic, of very low fertility, droughty and susceptible to wind erosion.

The vegetation is a ferny open woodland I dominated mainly by E. botryoides, with Banksia spp. and Pteridium esculentum.

A study of the land in the Catchment of Gippsland Lakes - Vol 2 - land system Rotamah - image

An aerial photograph showing the causeway to Rotamah Island with a typical woodland of Eucalyptus hotryoides and Banksia species in the background

CLIMATE Rainfall, mean (mm) Temperature, mean (°C) Seasonal growth limitations	Annual 600 - 900; lowest July or August (40 - 70), highest October (60 - 90) Annual 12 - 14; lowest July (9 - 10), highest February (19 - 20) Temperature <10°C (av.): No months Rainfall < potential evapotranspiration: December – March
GEOLOGY Age, lithology	Holocene barrier and coastal foredune sand deposits
PHYSIOGRAPHY Landscape Elevation range (m) Relative relief (m) Drainage pattern Drainage density (km/km²)	Uneven sand sheets formed from a close sequence of beach ridge deposits 0 - 20 0 - 5 Nil 0
PRESENT LAND USE	Mostly uncleared: mainly within The Lakes National Park; some privately owned uncommitted lands

A study of the land in the Catchment of Gippsland Lakes - Vol 2 - land system Rotamah - cs

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

LAND COMPONENT Percentage of land system Diagnostic features	1 90 Ridges	2 10 Swales
PHYSIOGRAPHY Slope %, typical and (range) Slope shape	4, (2 - 8) Mainly convex	<1, (0 - 2) Concave or straight
SOIL
Parent material	Sand of marine origin
Description	No observations — probably leached acidic sand, pale or whitish in the subsurface, generally over coffee rock or bright yellowish brown sand; light coloured sand below
Classification	Probably Podzols; Uc4.3-, Uc2.3-, Uc4.2-, Uc2.2- Siliceous Sands; Uc1.21
Surface texture	Sand
Surface consistence	Loose or soft
Depth (m)	>2.0
Nutrient status	Very low
Available soil water capacity	Very low
Perviousness to water	Very rapid
Drainage	Somewhat excessive
Exposed stone (%)	0
Sampled profile number	-
NATIVE VEGETATION Structure of vegetation and characteristic species of dominant stratum (+ Predominant species)	Ferny open woodland I: Variable composition — species including E. botryoides, E. viminalis var. racemosa, Banksia serrata, B. integrifolia (near lake shores) and Pteridium esculentum

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 increased deep percolation and leaching	Nutrient loss	1,2; high	Not determined	Removal of trees	Increased movement of water to groundwater
Increased exposure of surface soil	Increased wind velocity over soil and increased detachment of sand	Wind erosion Wave erosion	1; high 2; moderate 2; moderate	Uncommon Uncommon	Clearing, overgrazing, road building and other earth-moving activities, rabbit burrowing, trafficking by stock and vehicles. Removal of protective reeds along shore line	Encroachment by sand Turbidity of lake waters
Increased physical pressure on soil	Increased compaction	Structure decline	1; very low 2; low - moderate	Not determined	Increased trafficking, overgrazing, export of organic matter	-
Increased soil disruption	Increased loosening of sand	Wind erosion Wave erosion	1; high 2; moderate 2; moderate	Uncommon Uncommon	As for wind erosion Above As for wave erosion above	Encroachment by sand Turbidity of lake waters
Comments: Regeneration of vegetative cover is poor in areas exposed to wind and wave erosion, and expensive remedial works may be required

Page top