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


Area: 52 km
2
Component and its proportion of land system
1
60%
2
30%
3
10%
CLIMATE
Rainfall, mm
Annual: 950 – 1,100, lowest January (45), highest August (135)
Temperature, 0oC
Annual: 13, lowest July (8), highest February (18)
Temperature: less than 10oC (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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