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Thompson Creek Land System

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The lower reaches of the Thompson Creek catchment spread out into a wide alluvial plain. The plain appears almost flat, but it slopes towards the sea. The highest inland parts are some 20 m above the present valley floor of Thompson Creek, and some mild dissection into the plain occur along the sides of this valley.

Road reserves and small shelter belts for stock contain the only remnants of the native vegetation. Low woodlands of Eucalyptus leucoxylon and Casuarina stricta appear to have been common, with Acacia pycnantha dominating the understorey. E. leucoxylon shows evidence of severe salt pruning several kilometres from the coast. Soils are duplex and sodic with dispersible subsoils.

These plains are used for grazing and cropping. Minor problems are encountered from gully erosion along the margins of Thomson Creek, and soil salting occurs in the lowest areas close to the Connewarre land system.
A Study of land in the catchments of the Otway Range and adjacent plains - thompson creek

A Study of land in the catchments of the Otway Range and adjacent plains - thompson creek
These flat plains are used mainly for grazing and cropping

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


Area: 29 km
2
Component and its proportion of land system
1
70%
2
20%
3
10%
CLIMATE
Rainfall, mm

Annual: 600, lowest January (30), highest August (60)
Temperature, 0oC
Annual: 14, lowest July (9), highest February (19)
Temperature: less than 10oC (av.) July
Precipitation: less than potential evapotranspiration October – mid April
GEOLOGY
Age, lithology

Deeply weathered Plio-Pleistocene fluviatile sand and clay
TOPOGRAPHY
Landscape

Flat to gently undulating plain near the south of Thompson Creek
Elevation, m
0 – 50
Local relief, m
5
Drainage pattern
Weak dendritic pattern with some deranged areas
Drainage density, km/km2
1.2
Land form
Plain
Alluvial terrace
Land form element
Middle and upper slope
Lower slope
-
Slope (and range), %
0 (0-2)
4 (2-10)
1 (0-2)
Slope shape
Linear
Convex
Linear
NATIVE VEGETATION
Structure

Low woodland

Open forest

Woodland
Dominant species
E. leucoxylon, Casuarina stricta, E. ovata
E. leucoxylon
E. leucoxylon, E. viminalis
SOIL
Parent material

Sandy clay

Sandy clay

Sand, silt and clay
Description
Yellow-brown sodic duplex soils, coarse structure
Yellow sodic duplex soils
Brown sandy loam soils, uniform texture
Surface texture
Sandy loam
Sandy loam
Sandy loam
Permeability
Low
Moderate
High
Depth, m
>2
>2
>2
LAND USE
Cleared areas: Dairy farming and beef cattle grazing on mainly improved pastures; some cereal cropping
SOIL DETERIORATION HAZARD
Critical land features, processes, forms
Dispersible soils are prone to gully erosion. Sodic subsoils, low permeability and high water tables lead to soil salting.
Sodic subsoils and high water tables lead to soil salting.
Shallow saline water tables lead to soil salting, waterlogging and soil compaction. High discharge rates along watercourses lead to streambank erosion.
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