South Sister St. Marys, Tasmania

South Sister

geomorphologist reports ...

Dr. Leonie van der Maesen, Geomorphologist
Department of Physical Geography
Utrecht University

Observations of the area known as the South Sister, St. Marys, Tasmania. January 2005

The impact of logging on the environment is difficult to assess. The only way to arrive at a scientifically underpinned conclusion is to conduct a long-term investigation similar to what I am involved with in Western Australia (1992-2004). Such a study should be interdisciplinary and should involve:

The methodology of such investigation should include the use of maps, aerial photographs, satellite imagery, soil profiles, rain gauges at sites, expert assessments and a recent inventory of the flora and fauna.

The study in Western Australia has indicated that clearance of natural vegetation, particularly mature trees with an elaborate root system has a profound impact on the landscape and hydrology, and causes severe erosion, particularly on slopes. Due to the impact of the heavy machinery, serious cases of soil compaction occur. Once a soil profile is destroyed, it will never recover. The impact of opening the canopy is that soil temperature will rise, and it may become more of a fire hazard. The introduction of plant diseases and weeds is inevitable.

The RFA was going to be assessed on cultural, landscape and geological values as well as biological values. Coupe NI114A of the Nicholas Range, near St Marys, has a high conservation landscape due to its geological formations and uniqueness (having just about every geological formation in a small area.)

The geology and geomorphology is very complex with faulting and folding, ancient volcanic activity, (the South and North Sisters are volcanic plugs), the formation of dykes and sills in the sedimentary rocks. This resulted in a difference in contour lines, slope angles from zero to 40 degrees.

The glacial impacts and erosive forces have formed this landscape. The coal seams and sandstone (both Triassic) indicate that this area has had a different climate regime.

The topography varies a great deal. It contains many important catchment areas and creeks.

According to the Mines Department 'the major landslip areas appear to be associated with steep slopes underlain by dolerite talus which in turn overlies Triassic sandstone and coal measures'.

The Natural and Cultural Values Evaluation Sheet (6) Soil and Water, Aug 19, 2003 and Dec 12, 2004, A. Crowden) states:

This applies to most areas visited. Sheet erosion, slumps and landslips were observed along the road. This is in agreement with the observation around the Mt Nicholas-North Sister-Cheeseberry Hill area of which some were extensive (Sloane, D.J. 1976).
'All landslips have resulted from the failure of a dolerite talus or solifluction deposit, present as a thin mantle on the sandstone and coal measures. Seepages and springs are associated with slips, the groundwater moving along the Triassic bedrock-dolerite talus interface' etc. Sloane, D.J. 1976.


The microclimates of this area are as follows (Bureau of Meteorology, Tasmania); German Town has a rainfall of approximately1000 mm per year, Gray 1200 mm per year and it is estimated that South Sister is approximately1500 mm per year. DPIWE (1999) predicts rainfall at the proposed logging sites at 1300-1500 mm/yr.

Problems with this data is that it is generalized data, there is no information about the various proposed coupes, data on the various slope angles, no rain intensity figures, no data on the temperature and wind speed, evapo-transpiration.


Although generalized data on soils is available, it is not sufficient to do a proper assessment unless soil profile descriptions are available.

No conclusions can be drawn about the individual sites due to a lack of scientific information.


Insufficient data is available about the sites. No measurements were taken over a period of time, the behaviour of groundwater oscillations, and the runoff occurrences cannot be established.

Flora and fauna

The pre-logging compulsory inventory of the flora and fauna is not available, (perhaps even non existent).

Social and economic impact

Due to the inexperience of the local inhabitants, the lack of available scientific information, the lack of support of the Government by supplying proper aerial photographs and a non-existent methodology for assessment, many factors are still unknown.

In my opinion no logging should take place on Coupe NI114A until all the parameters have been studied concerning the impact of the logging on the natural and social environment.

During the RFA special social impacts (high recreation values etc) were included as were the importance of 'special places'. It is very clear that the two Sisters area, near St Marys is one of these ‘special places’ to the local community.


The areas visited on and around coupe NI114A included: 598100E/5401000N, 597900E/5401100N, 598300E/5401300N, 598400E/5401200N and 598900E/5400300N.

The specific sites visited that are to be logged included the areas adjacent to the South Sister Road (excluding the Eucalyptus brookeriana reserve at the start of the road) and then northeastern part of the coupe (598200E/540100N).

The elevation range of the topography where logging is about to commence varies between approximately 580 m and 685 m.

In general, areas visited in the northeast where logging had recently occurred, showed evidence of serious breaches of the Forest Practices Code where logging debris has entered creeks. These breaches already show a lack of monitoring so there is reason to believe that it will be no different in this proposed logging coupe.

Where there is a whole range of already identified wells/springs - I have found absolutely no scientific evidence that these and others will not be affected should logging occur. For example, there has been no drilling or physical evidence regarding the existence of the aquifer range. No data has been produced.


It is also not feasible to generalise about the homogenous situations regarding microclimate conditions, as these are known to vary according to aspect, wind direction and velocity, sun duration and areas can occur in rain shadows. These are important factors in hydrology of the site. These parameters will have an affect on the hydrology of the site, and this has not been taken in to consideration in my reading of the reports.

Likewise there has been absolutely no scientifically explained rationale as to how operations will be affected by climate change, such as the impacts on regrowth and water tables.

31 January, 2005


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