Yahoo Creek Land System

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North of the Gellibrand River, Cretaceous sandstones and mudstones outcrop in the valleys of the Yahoo Creek, Gum Gully Creek and an unnamed creek to the west of Black Bridge road. These sediments belong to the Moonlight Head Beds of the Otway Group. Slopes are steep and valleys are narrow, in sharp contrast to the rounded hills of adjacent Tertiary sediments.

The soils are similar to those found on other outcrops of Cretaceous sediments in the Range, with the exception that surface horizons contain appreciably more sand and the parent material is usually highly weathered. Open forests of Eucalyptus obliqua, E. ovata and E. aromaphloia are similar to those found on the drier slopes of the Forrest land system.

Most parts of the valleys remain virtually uncleared and quite remote. Hardwood forestry is the main land use, although the rugged terrain makes access difficult. Some softwood plantations have been established in the catchment of Yahoo Creek. Landslips occur on these soils under native forest, and the incidence increases dramatically following clearing. Sheet erosion and gully erosion are also prone to occur.

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

The steep and rugged hills surrounding Yahoo Creek are difficult
to manage. Scrub regrowth rapidly takes over recently cleared slopes.

Area: 32 km²	Component and its proportion of land system
Area: 32 km²	1 35%	2 45%	3 15%	4 5%
CLIMATE Rainfall, mm	Annual: 850 – 1,000, lowest January (40), highest August (130)
Temperature, 0^oC	Annual: 12, lowest July (7), highest February (18)
	Temperature: less than 10^oC (av.) June – September
	Precipitation: less than potential evapotranspiration November – March
GEOLOGY Age, lithology	Low Cretaceous highly feldspathic sandstone and mudstone (Moonlight Head Beds)
TOPOGRAPHY Landscape	Deeply dissected hills to the north of Gellibrand River
Elevation, m	60 – 270
Local relief, m	110
Drainage pattern	Dendritic with small radial areas
Drainage density, km/km²	3.0
Land form	Hill
Land form element	Steep slope	Crest, upper slope	Slope	Swale, gentle lower slope
Slope (and range), %	50 (20-70)	15 (2-30)	35 (15-45)	13 (1-25)
Slope shape	Linear	Linear	Linear	Concave
NATIVE VEGETATION Structure	Open forest	Open forest	Open forest	Open forest
Dominant species	E. ovata, E. obliqua, E. radiata, E. aromaphloia, E. viminalis	E. obliqua, E. ovata, E. aromaphloia, E. radiata	E. viminalis, E. obliqua	E. viminalis, E. obliqua, Acacia melanoxylon
SOIL Parent material	In-situ weathered rock, colluvial rock	In-situ deeply weathered rock	In-situ weathered rock	Colluvium
Description	Stony brown gradational soils	Yellow-brown gradational soils, coarse structure	Brown gradational soils	Dark brown gradational soils
Surface texture	Fine sandy loam	Sandy clay loam	Loam	Loam
Permeability	High	Low	Moderate	Moderate
Depth, m	0.7	1.2	0.9	>2
LAND USE	Uncleared areas: Hardwood forestry for sawlogs, posts and poles; nature conservation; water supply Minor cleared areas: Sheep and beef cattle grazing; water supply
SOIL DETERIORATION HAZARD Critical land features, processes, forms	Stony shallow soils with weak structure and low water-holding capacity on steep slopes are prone to sheet erosion and landslides.	Soils of low permeability on the steeper slopes are prone to sheet and rill erosion. Dispersible subsoils are prone to gully erosion.	Clay subsoils on steep slopes subject to periodic saturation are prone to landslips. Steep slopes are prone to sheet erosion.	Weakly structured soils receiving run-off from adjacent hills are prone to scour gullying, siltation and flooding.

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