Soils

Seven Soil Landscapes have been recognised in Moggill Creek Catchment.

The Pullenvale Soil Landscape occurs across the upper catchment and comprises low hills, often steep, formed on metamorphosed greywacke, shales and phylittes of the Neranleigh-Fernvale formation. This part of the catchment has steep drainage gradients resulting in much higher runoff velocities than occur further down the catchment. The sediment movement during high rainfall events poses considerable challenges to riparian land holders in their quests to stabilise stream banks and beds. Common soils are gravelly shallow Rudosols (rudimentary development) which occur from the crests to lower slope positions. Deeper or more developed soils such as Dermosols, Kandosols which have little structure in the subsoils, can occur on mid to lower slopes. Dermosols have some evidence of structure and may have higher clay content in the sub soils; they can be dark or brown to reddish brown in the subsoil.

The range of rock types in sediment beds influences the surface and sub soil characteristics and where the beds have been tilted substantially a range of soils can occur across a short distance. Most of the Rudosols in the crests to mid slope positions can have substantial gravel in the surface and little weathered material sitting on relatively unweathered rock. Dermosols and Kandosols tend to occur in the drainage lines and other moister parts of the landscape which leads to more weathering of parent materials. Steeper slopes tend to result in higher erosion rates and this limits soil development and accumulation.

The Toowong Soil Landscape has developed in the east edge of the catchment on low hilly lands cut into the Bunya Phyllites. The steeper upper slopes and narrow crests have thin gravelly Rudosols and irregular outcropping rocks. Associated in the upper and mid slopes are shallow gravelly surfaced Kandosols with weakly structured red or brown clay subsoil grading to weathering rock. In moister lower slopes the soils tend to be deeper with mottled red and yellow coarsely structured clay subsurface horizons. In some of these mid and lower slope areas the soils may be Kurosols which have a distinct texture contrast between the surface and sub-surface horizons.

The steep hills of basic volcanic on the southern edge of the upper Brookfield area, and in the middle of the catchment separating the upper part of Wonga creek sub-catchment from Moggill Creek is the Elphinstone Soil Landscape. This landscape gets its name from Mt Elphinstone in the southern part of the catchment. What appear to be scree slopes occur on some upper slopes; soils are shallow stoney Dermosols and Kandosols or Chromosols.

The Brookfield Soil Landscape also developed on basic volcanic rock, occurs in the central and south parts of the catchment and is comprised of low hilly lands and has lower slopes than the Elphinstone soil landscape. The main soils are shallow Dermosols on ridges and upper slope areas, with reddish- brown Kandosols with weak structure in the B horizons on the mid and lower slopes. These areas were some of the first areas cleared for timber and then cropped and/or grazed.

The Kenmore Soil Landscape in the mid to lower part of the catchment comprises low hills also on the Neranleigh-Fernvale formation and forms the lower parts of the catchment below the Pullenvale Soil Landscape. Depending on the rock types and topographic positions, the range of soils is similar to those in the Pullenvale landscape. Most of the soils apart from some in the lowest positions of this landscape have low fertility; those in the lower moister parts of the topography with dense vegetative cover have more soil organic matter, more soil flora and fauna and therefore tend to have slightly higher fertility. Included in this landscape are small areas of basic volcanic rock with Dermosols and Rudosols which are also of low fertility. The wider valley floors have been widely used for agriculture, grazing of cattle or horses and peri urban dwellings on acreage properties. Many of these have no commercial operations. The main difference to the other soil landscapes on Neranleigh-Fernvale beds is the larger area of more moderate sloping lands and wider valley floors which have allowed a wider range of soil characteristics. They include more developed and deeper light brown to grey brown and reddish brown Kandosols, Dermosols, Kurosols and occasionally Chromosols which have a texture contrast between the surface and sub-surface soil horizons in the low sloping areas.

The Moggill Creek Soil Landscape occurs in the valley floors associated with riparian zones of the main creeks. The soils are formed from a range of sandy and clayey alluvium, and include Kandosols, and Dermosols; they are commonly more than a metre in depth, can be sandy to clayey in texture and in the lowest part of the catchment from Rafting Ground Road to the Brisbane River are likely to be overlying other sedimentary materials which are considered to be buried soils. These are the lands most suitable for agricultural and grazing activities, but are also excellent for sporting and other recreational activities. Much of this landscape in the bottom third of the catchment is subject to flooding during episodic events.

Further reading

Beckmann, G., Hubble, G. and Thompson, C. (1987). The Soil Landscapes of Brisbane and South-east Environs. CSIRO, Australia. 77 pp.
Brisbane City Council (2007). Know Your Creek, Moggill Creek. 46pp. Available free or download from www.brisbane.qld.gov.au

Willmott, Warwick and Stevens, Neville (1992). Rocks and Landscapes of Brisbane and Ipswich. Geological Society of Australia, Queensland Division. 72 pp.

Link to reference somewhere for The Soil Landscapes of Brisbane and South-eastern Environs. Beckmann, G.G., Hubble, G.D. and Thompson, C.H. (1987). The older Great Soil Group names used by Beckmann et al have been interpreted and given names that follow Soil Orders of the Australian Soil Classification by Isbell, R.F. 1996. No rigorous field examinations have been made to verify these interpretations.

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