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South Maroochy River


The South Maroochy river rises on the northern slopes of Towen Mountain, a small range complex that is a spur of the Blackall Ranges, which form the western boundary of the subcatchment. It confluences with the North Maroochy River near the town of Yandina to form the estuary. Within the South Maroochy subcatchment are two of the major dams within the region, Cooloolabin and Wappa.

 The landform of the headwaters is a small hill complex of Laterised Tertiary basalt, grading to low, undulating hills founded on the same landform that make up the upper half of the subcatchment. Throughout the upper subcatchment, the landform never develops a continuous alluvial plain of any size as this is precluded by the steepness of the terrain through which the river flows. However, there are small creek lines and some valley flats near the end of the upper half, at the boundary of this particular landform.

 The lower half of the subcatchment consists of low steep hills formed on Rhyolite and Andesite. The land form in this area is similar to that found in the upper subcatchment, low, steep hills that prevent the development of alluvial plains with only small valley flats being observed.

 Once the river exits these low hills, it is able to form a short alluvial plain just prior to its confluence with the North Maroochy River. This alluvial plain consists of undifferentiated freshwater sediment.
 

South Maroochy River below Wappa Dam. Note extensive riparian vegetation on both banks.

The upper subcatchment supports remnant patches of rainforest species, but the majority of this area has been cleared for grazing. The areas remaining under vegetation are usually those that are too steep for clearing, or on the tops of steep hills. The lower areas of the upper subcatchment still support remnant stands of Flooded Gum (Eucalyptus grandis) in riparian areas.

 


South Maroochy River
At a Glance

 Major towns – Yandina, Cooloolabin

 Subcatchment Area – 9134 ha

 Rainfall – 1680 mm/yr (Yandina)

 Major Land Uses:

 Native Vegetation – 4280 Ha (47%)

 Grazing –  3050 Ha (33%)

 Cropping – 785 Ha (8.5%)


The slopes and summit of the Blackall range, which forms the western boundary of the subcatchment, supports extensive areas of Blackbutt (Eucalyptus pilularis) and Grey Gum (Eucalyptus punctata) open forest. Other species found in this area are Turpentine (Syncarpia glomulifera), Forest She Oak (Allocasuarina torulosa) and Tallow Wood (Eucalyptus microcorys). This vegetation also occurs on the low steep hills of the lower subcatchment, which are an extension of the Blackall Range.

The alluvial floodplain that forms the bottom end of the river is almost entirely cleared for agriculture, but still has some isolated individual Forest Red gums (Eucalyptus tereticornis).
The main land uses in the South Maroochy River subcatchment are native vegetation, grazing and crops, which collectively occupy nearly 90% of the area. Of these, native vegetation is the highest user of land area, covering 47% of the subcatchment. The South Maroochy is different to the other subcatchments in that more remnant vegetation is contained within reserves than on private land. Grazing, which occupies 33% of the area is found predominately in the upper subcatchment, where the landform and soil type are more conducive to these pursuits. Cropping, which covers only 8% of the subcatchment, is the third largest land use by area. This category includes all row cropping and tree crops.