Gellibrand River Land System

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Many of the larger rivers in the wetter parts of the study area have extensive flood plains. Areas large enough to map exist on the Barham, Aire and Johanna Rivers as well as the Gellibrand River and its tributaries.

The landscape is generally flat, but irregular areas occur in the form of infilled meanders and minor terraces. In general, most areas are poorly drained, with stunted vegetation. However, closer to the drainage lines, the improved drainage often results in conditions more favourable for plant growth.

Most of these alluvial flats have been cleared and provide valuable summer grazing for dairy farms along the valleys.

Areas prone to waterlogging have been drained and improved pastures established. However, the remoteness of the valleys, set among very infertile surrounding land, has hampered agricultural development.

A Study of land in the catchments of the Otway Range and adjacent plains - gellibrand

The Aire River has an extensive floodplain with many swamps
and lakes where it emerges from the Otway Range near Hordern Vale.

Area: 52 km²	Component and its proportion of land system
Area: 52 km²	1 60%	2 30%	3 10%
CLIMATE Rainfall, mm	Annual: 950 – 1,100, lowest January (45), highest August (135)
Temperature, 0^oC	Annual: 13, lowest July (8), highest February (18)
	Temperature: less than 10^oC (av.) June – September; July only near the coast
	Precipitation: less than potential evapotranspiration early November – late March; December – January near coast
GEOLOGY Age, lithology	Recent alluvium derived from the Otway Range and surrounding foothills.
TOPOGRAPHY Landscape	Alluvial flood plain of the Gellibrand, Aire and Barham Rivers
Elevation, m	0 – 100
Local relief, m	3
Drainage pattern	Major meandering stream with deranged tributaries
Drainage density, km/km²	1.3
Land form	Alluvial terrace		Streambank, cut-off meander, lower terrace
Land form element	Poorly drained lower reaches	Well-drained upper reaches	-
Slope (and range), %	1 (0-2)	0 (0-1)	2 (0-5)
Slope shape	Linear	Linear	Convex
NATIVE VEGETATION Structure	Low woodland	Tall open forest	Tall open forest
Dominant species	E. obliqua, E. radiata, E. ovata	E. viminalis, E. obliqua, E. ovata, Acacia melanoxylon	E. viminalis, E. obliqua, Acacia melanoxylon
SOIL Parent material	Alluvial clay, silt and sand	Alluvial clay, silt and sand	Alluvial sand, silt and clay
Description	Grey gradational soils	Brown gradational soils, weak structure	Brown sandy loam soils, uniform texture
Surface texture	Fine sandy loam	Fine sandy loam	Sandy loam
Permeability	Very low	Moderate	Very high
Depth, m	>2	>2	>2
LAND USE	Cleared areas: Dairy farming and beef cattle grazing on improved pastures; row and fodder cropping; water supply Uncleared areas: Water supply; nature conservation; hardwood forestry for sawlogs
SOIL DETERIORATION HAZARD Critical land features, processes, forms	High discharge rates along watercourses lead to flooding and siltation. High seasonal water table and low permeabilities lead to seasonal waterlogging and soil compaction.	High discharge rates along watercourses lead to flooding and siltation. Weakly structured soils are prone to surface compaction.	High discharge rates along watercourses with weakly structured soils lead to streambank erosion and siltation. High seasonal water table in some areas leads to waterlogging.

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