Seacombe (Sm)

	Area: 85 sq. km (0.4%) Seacombe land system occurs on parts of the prior and inner barriers. Where the inner barrier is still intact there is an undulating sand sheet, produced by a series of broad but closely spaced beach ridges parallel to the coastline. The formation is of Pleistocene age, but more recent aeolian disturbance producing an incipient dune-like surface has occurred in areas like Sperm Whale Head. More severe, peripheral, aeolian attack of these beach ridges has created larger, mostly parabolic dunes; these dunes are mapped in Banksia land system. In other areas, the inner and prior barriers suffered partial dissection during the last major sea level fall and have since undergone lacustrine re-working to produce beach ridges of lower relief. The orientation of the beach ridges varies with the orientation of the paleo-lacustrine shores, rather than being parallel to the coastline. Often the beach ridges are no longer distinct and a sand sheet with an uneven surface occurs. Where there has been significant aeolian disruption of these lower ridges, the water table has been excavated and dunes with swampy cores occur.	Very low sand ridges form a large uneven sand plain typical of Seacombe land system
The sands may originally have contained shell fragments and carbonates, but now the soils are leached, infertile and strongly acidic, particularly in the topsoil. They also generally appear to have developed iron-indurated pans (coffee-rock) mostly at greater depths (deeper than 1.5 m) than in similar soils elsewhere in the region. Being of sandy texture throughout, the soils are droughty and susceptible to wind erosion. There is a moderate salinity hazard because of a saline, ground-water table close to the surface of the swales and low-lying areas. The vegetation is mainly a heathy open woodland of E. nitida and Banksia serrata. It is replaced by an open woodland of E. viminalis var. racemosa and B. serrata with Pteridium esculentum on lower moister site

CLIMATE Rainfall, mean (mm) Temperature, mean (°C) Seasonal growth limitations	Annual 500 - 800; lowest January (30 - 50), highest October (40 - 70) Annual 12 - 14; lowest July (9 - 10), highest February (19 - 20) Temperature <10°C (av.): No months Rainfall < potential evapotranspiration: November – March
GEOLOGY Age, lithology	Pleistocene sandy coastal barrier deposits
PHYSIOGRAPHY Landscape Elevation range (m) Relative relief (m) Drainage pattern Drainage density (km/km²)	Marine and lacustrine sand sheets formed from a series of relict beach ridges 0 - 20 0 - 5 Nil 0
PRESENT LAND USE	Mostly uncleared: within the Gippsland Lakes Coastal Park, The Lakes National Park and Blond Bay State Game Reserve; apiculture; bush grazing of cattle (very limited) Minor cleared areas: grazing of sheep and cattle

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

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

LAND COMPONENT Percentage of land system Diagnostic features	1 40 Closely spaced beach ridges forming gently undulating surface	2 8 Swales	3 52 Sand sheets of low and uneven relief. Occasional swamps in low-lying areas
PHYSIOGRAPHY Slope %, typical and (range) Slope shape	Variable, (0 - 20) Convex and concave	<1, (0 - 2) concave	1- 2, (0 - 5) Straight but uneven
SOIL
Parent material	Marine and lacustrine sand, locally redistributed by wind
Description	Limited observations — leached acidic sand, black or dark grey at the surface, pale brown or whitish in the subsurface often over contrasting dark yellowish brown sand or coffee rock; light yellowish coloured sandy subsoil. Depth to coffee rock or the dark yellowish brown sand variable, probably between 1 and 2 m
Classification	Podzols, Siliceous Sands Uc4.31, Uc2.32, probably also Uc4.2-, Uc2.2- and Uc1.21
Surface texture	Sand
Surface consistence	Loose or soft when dry
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	Nicholson (1978), profile 755	-
NATIVE VEGETATION Structure of vegetation and characteristic species of dominant stratum (+ Predominant species)	Mainly heathy open woodland I: E. nitida, Banksia serrata (either predominant) Understorey dominated mostly by Leptospermum myrsinoides or Thryptomene micrantha On moister sites, ferny open woodland I: E. viminalis var. racemosa+, B. serrata, Pteridium esculentum		Mainly open woodland I: E. viminalis var. racemosa+ with Pteridium esculentum Swamps with Gahnia spp. or Juncus maritimus and/or Lepidosperma longitudinale and usually with fringe of Melaleuca ericifolia or M. squarrosa

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: a) increased deep percolation and leaching b) raised groundwater table	Nutrient loss Salting	1,2,3; high 2,3; low	Not determined Uncommon: isolated occurrences	Removal of trees Reduced plant water use in the catchment	Increased movement of water to groundwater Raised groundwater table
Increased exposure of surface soil	Increased wind velocity over soil and increased detachment of sand	Wave erosion Wind erosion	2,3; moderate 1,2,3; high	Uncommon Uncommon: but locally severe	Clearing, burning, overgrazing, road building and other earth-moving activities, trafficking by stock and vehicles.	Increased turbidity of water Encroachment by sand
Increased physical pressure on soil	Increased compaction	Structure decline	1; low 2,3; low	Uncommon	Increased trafficking, overgrazing, export of organic matter	-
Increased soil disruption	Increased loosening of sand	Wind erosion Wave erosion	1,2,3; high 2,3; moderate	Uncommon: locally severe Uncommon	As for wind erosion above As for wave erosion above	Encroachment by sand Increased turbidity of water
Comments: Regeneration of vegetative cover poor in areas exposed to wind and wave erosion and expensive remedial works may be required. An area of salting occurs just south east of Lake Wellington.

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