Noosa Council Planning Report - 26 Sallwood Ct, Pinbarren. (3)

the months of December through to March to ‘Moderate or Low’ for the rest of the year.

 Jan      Feb      Mar      Apr    May     Jun      Jul       Aug    Sep   Oct   Nov     Dec
 H        H        H        M      M       M        L         VL     M     M     M       H
Table 1: Erosion risk ratings based on monthly rainfall erosivity.

Risk for erosive rainfall and subsequent sediment loss are higher during the months of December
to March. The clearing and drainage works occurred outside the high risk months which was a key
project objective.


2.2 Water
Drainage runs through the property and the whole property is within its catchment. Department of
Natural Resources Mines and Energy (DNRME) Watercourse Identification Map within Queensland
Globe Inland Waters (accessed on 20 March 2022) indicates that the drainage line is not a
determined drainage feature until it reaches Pinbarren Creek (approximately 0.5km downstream)
that is regulated under the Water Act 2000. Department of Environment and Science
Environmental Report (Refer Attachment A) recognises the drainage line on the property as a
waterway with potential values for aquatic habitat and connectivity. Aerial photos show that much
of the upper catchment from the property has low naturalness and the drainage line has been re-
aligned and rip rap & vegetation protected.

There was a risk during clearing and earthworks that sediment would be released to downstream
environments. Appropriate measures appeared to be in place (i.e. mulch bunds and the existing
dam used as a sediment trap). Permanent drainage/channel protection matched existing rip rap
protection which would have been hydraulically sized to the upstream catchment, slope and
expected flows (i.e. D50=400mm). Inspections have identified a stable non-eroding environment
with natural recruitment of native sedges and grass becoming established. All works completed
have experienced a beyond average wet season with several large rain events (>300mm in 24hrs).
It is therefore anticipated and evident that this change in landscape has improved the overall
environmental values of the property including improvements to; drainage protection and capacity,
erosion protection, overall water quality to the catchment.




2.3 Soil / Land Management
Soil Types
Soil mapping and site evaluation identifies most of the property has medium clays overlying clayey
subsoils (texture contrast soils) with low organic matter. The Mary River Catchment Coordination
Committee’s report “Grazing land types of the Gympie district” (Department of Employment,
Economic, Development and Innovation, Feb 2017) provides the following soil characteristics; high
moisture holding capacity; moderate to high soil fertility; erosion risk as susceptible to scouring and
slumping during high rainfall events.

Council overlay mapping indicates a medium risk Landslide Hazard within part of the property
mainly due to the topography of the land. Existing topography features show no steep sections on
the property.

Soils results indicate that although the topsoils are non-dispersive and the existing landscape has
moderate erosion risk, once soils are exposed the risks of erosion is high. Therefore, the
management of exposure to soil is a major construction element to manage and did govern the




Ecological Assessment Report 26 Sallwood Court, Pinbarren                                   Page 6 of 11