South Sister St. Marys, Tasmania

South Sister Evidence

forestry 'scientists' exposed

A Review of My Experience as an Expert Witness
in Weston & Others v Forestry Tasmania (revised April 2006)
by Ralph Rallings


The following is an update and upgrade of my original review paper of December 2005. The review covers my experience as an expert witness for applicants in the matter of the effect of forestry operations on land stability within the proposed Coupe NI 114A on South Sister.

Since December 2005 I have written on two occasions to the Hon B Green, Minister for Infrastructure, Energy and Resources concerning false and misleading evidence that was included in Ref 1. I have received replies from the Minister. The substance of these letters and replies comprise the major component of the additional information include in the update.

Reference 1 was to be tendered as evidence to a hearing of the Resource Management and Planning Appeal Tribunal. It was only subsequent to the applicants' withdrawal from the hearing was it realized that information within the document was false and misleading. The false and misleading information was a primary factor in the considerations that led to the withdrawal.

The update also includes information from my original evidence (Ref 2 & 3), but which was not included in the original review. In addition to this, I have undertaken some much needed rewording and rearrangement in order to improve clarity. There is within this update a much stronger expression of concern about the false and misleading information. This stronger expression arises because I have been unable to cause the Minister to address this issue, an issue that should be of great concern to anyone dedicated to honest and open government.

This was my first experience in a forestry related matter. I have not been able to assess if I have experienced an aberration of normal practice or not. I thought, though, that there might be value in documenting my experience for others to make this assessment.

I have thought about the following, and I would hope that as you examine this document, you might do so as well:

At the outset, I should emphasise that while the matter centres on Forestry Tasmania, I have had no contact with this organization and that nothing in the following directly reflects on Forestry Tasmania.

The Site and the Application

The coupe of about 160ha lies 5km north of St Marys, near Tasmania's east coast. It partly encircles the eastern and southern flanks of South Sister (Attachment 1), at elevations generally between 600 and 700m. South Sister is towards the eastern end of the Nicholas Range, which comprises a steeply sided spine of Jurassic age dolerite overlying Triassic age sandstone, siltstone and coal. The surface of these lower sediments is overlain by talus, derived from the dolerite. The area has an average and median rainfall in the order of 1100 mm/annum, spread fairly uniformly over the year.

The applicants had originally sought to prevent logging within the coupe. They were concerned that logging would disrupt springs that were their water supplies, and also feared that logging would initiate slope instability. I understand that in the weeks leading up to the hearing, the applicants withdrew the grounds relating to water supply impacts and approached Forestry to exclude the three areas indicated in Fig 1, an area of 33ha. I also understand that this proposal was not acceptable to Forestry Tasmania and the matter was scheduled for a Resource Management and Planning Appeal Tribunal hearing to commence on 3 October 2005. The applicants withdrew a few days prior to this date. My understanding of some of the reasons for the withdrawal is indicated in the following.

Scope of this Review

This review is concerned only with issues relating to slope stability and mainly those in the NE facing slopes of the proposed coupe. The topics discussed include:

This review gives considerable attention to the Supplementary Proof of Evidence (Ref 1) provided by Dr P McIntosh (an officer of the Forest Practices Authority, engaged as a consultant by Forestry Tasmania) and Mr B Weldon on 28 September 2005. This particular report, which was intended as evidence to a Resource Management and Planning Appeal Tribunal hearing scheduled for the following week, contains false and misleading information on an issue central to the slope stability issue.

From the very beginning of my involvement in this matter, I wondered how and why Forestry Tasmania and the Forest Practices Authority (FPA) could take a stand that was so contrary to conventional wisdom on slope stability. It has been only since I began to delve into and understand the approval and appeal processes and the working relationship between these two entities that I have approached an understanding as to why this could be so.

I have worked in geotechnical engineering for over 40 years. I was a member of the Australian Geomechanics Society's Task Force that developed the standard national reference on landslide risk, Landslide Risk Management Concepts and Guidelines (see Ref 4), and I am a member of the current Task Force that is updating these Guidelines.

Advice Given on Slope Stability

I provided advice to the applicants (a number of local residents concerned about the potential impacts of forest harvesting on the coupe). My advice to them has been:

This advice is no more than conventional wisdom. For example, Geoscience Australia (Ref 6) identifies the removal of vegetation as a trigger for landslides, as does the Australian Geomechanics Society (AGS, 2000 - see Ref 4). Similar advice was provided by David Stapledon (Ref 7). David's expertise in Engineering Geology is recognized internationally.

Two consultants providing advice to Forestry also expressed caution. Lane1 (Ref 5) stated 'I agree with Dr Leaman that working the eastern face of South Sister does pose a potential problem for land stability and perhaps for some springs. Much of the most sensitive area has been excluded from the logging plan.' At that time he would not have been aware of the existence of Slide B within the Coupe.

Dr O' Loughlin (Ref 16) had this to say:

'Forest thinning on coupe N1114A will result in reduced evapotranspiration during the first several years, and thus an increased volume of water will be retained in the soil, and more will percolate to groundwater. This will generally raise groundwater levels in the talus underlying the coupe, and cause the saturation areas at seepages and stream heads to expand.

Using an enhanced rate of percolation to groundwater of 100 mm per annum immediately after forest thinning (see above), then groundwater levels in the talus would rise by about one metre in a year (assuming a porosity of 10%). The cumulative increase over several years could exceed this, but the eventual rise in groundwater level would be limited by the increased discharge of subsurface water at springs and seepage areas. Nevertheless, pore pressures could increase where the talus is saturated, and marginally decrease slope stability. However, the actual increase in pore pressure would depend on the hydraulic conductivity of the talus deposits and the existence of preferred water pathways through them. (Higher hydraulic conductivity or preferred pathways have the effect of relieving or reducing pore pressures.) Because there is no information on the thickness, strength or water conducting properties of the talus, or its groundwater levels, it is not possible to comment on the significance (with respect to slope stability) of enhanced percolation of water into the talus after forest thinning.'

O'Loughlin's statement neatly summarises the issues concerning the relationship between the removal of trees and pore pressure increase, the complexity of these relationships, as well as some of the information that is necessary regarding slope stability. It would have been more precise to replace 'marginally decrease slope stability' with 'marginally decrease the factor of safety'. The latter is sure to happen, but the effect on the slope is not predictable, and could vary from no effect to catastrophic.

My involvement began in late January 2005, after the plan for the coupe had been certified, following a request from Dr Frances Daily of the Save Our Sisters Action Group to peruse the available information. I was particularly interested and concerned by the comment of Dr McIntosh (an FPA officer) (Ref 8) that:

'almost all parent soils on slopes in Tasmania have formed in the past by previous erosion under a different climate from that now prevailing and past failure is not necessarily an indication of present risk'

While the statement is accurate because of the inclusion of 'not necessarily', it is misleading with respect to the risks posed by past failures. Past failures are probably the best indicator of present and future risk. I saw the matter in Perera's terms (see Ref 9):

'They [fossil landslides] commonly have developed under different climatic conditions and are not likely to move again under present climatic and vegetative conditions, unless human intervention tips the balance'

Being well aware that the removal of trees was one of the most common causes of landslide reactivation, I agreed to provide advice to Dr Daily and visited the site in late January 2005. I found that there had been a history of slope instability within the vicinity of the coupe and that no landscape mapping had been taken, either within or adjacent to the coupe. My report outlined the appropriate scope of further investigations.

During this visit, I was taken to the location of two major slides by J McGivoren, who previously was the operations manager for the Huntsman Mine.

A major slide was reputed to have occurred at Sea View farm in about 1960. The features of a slide, several hectares in extent, were clearly evident at the reputed site. It is also on record that a major slide occurred at the Jubilee Mine. These major slides were all within the same geological complex, the Nicholas Range, as the coupe. I interpreted their occurrence as strong evidence that the landscape within the Mt Nicholas Range is relatively unstable and sensitive to human activity.

A much smaller slide (10x rather than 100x metres in extent) was observed on Dublin Town Rd. This slide was reputed to have occurred in 1984/85 and its reported location is the subject of the false and misleading information issue.

Attachment 1, originally produced by David Stapledon (Ref 7), locates two large landslides (Slide A and Slide B, both several hectares or more in area) just above Dublin Town Road and near the northeast corner of Coupe NI 114A. Based on this figure, I recommended in my Supplementary Proof of Evidence (Ref 3) that all of the eastern face of the coupe should be excluded from logging. The limits of the areas recommended for exclusion have been added to this figure.

The original investigations undertaken by Forestry Tasmania and the FPA had located Slide A and quite correctly they had removed the area of the slide from the harvestable area of the coupe. However, they failed to locate Slide B. Slide B is a very prominent and recognizable feature, from aerial photographs, contours and on the ground. It is in the order of 5 hectares in area.

The subsequent position adopted by Forestry Tasmania and FPA experts has been that there was no evidence of recent activity in Slide B, that it was an old slide on flatter terrain than Slide A and therefore:

I argued that the removal of trees in areas of past instability is unnecessarily risky, due to the following issues:

Even in situations where it is considered that the probability of landsliding is low, there is no sound justification for increasing the risk that might arise from reactivation by removing trees from landslide-prone areas2. The Australian Geomechanics Society (Ref 4, Appendix G - 'Risk Levels: Implications') states that activity in low risk areas is usually accepted subject to 'treatment requirements and responsibility to define and maintain or reduce risk.' (my emphasis)

Removing trees almost invariably increases the risk of reactivation of a landslide, therefore the removal of trees in landslide prone areas should always be avoided.

Questions of Proof and Certainty

To be successful against Forestry Tasmania in the application before the Resource Management and Planning Appeal Tribunal, it was necessary to show that the forestry operations were 'likely' to cause a landslide. It seemed to me that the onus of proof was the reverse of what I would see as appropriate and fair. In my view, the onus of proof should have been on the agency causing the potential damage to show that instability was 'unlikely', however the onus was placed on the applicants to show that instability was 'likely'.

I was asked to advise whether, in my opinion, the proposed forestry operation was likely to lead to instability or to induce/reactivate landslides. On further enquiry, I was advised that 'likely' was best understood in a legal sense as 'a real, rather than remote chance' of an event. This is the test that I tried to understand and to apply. The following provides a brief exploration of the meaning of 'likely'.

The Australian Geomechanics Society (Ref 4) identifies six levels of likelihood in relation to landslide activity. These are set out below, together with the indicative annual probability for each level:

Description Indicative Annual Probability
Almost Certain 10-1
Likely 10-2
Possible 10-3
Unlikely 10-4
Rare 10-5
Not Creditable 10-6


  1. In the usual sense of the word, 'remote' seems to align closely with 'unlikely'. However alignment between the terms in the above table and 'real, and not remote' runs into the problem that the former refers to an annual probability of occurrence, whereas the latter probably refers to the probability of occurrence over a particular period of time.
  2. An Indicative Annual Probability of 10-2 is equivalent to a 1 in 100 chance (1%) of the event occurring in a particular year. The chance of the event occurring in a 10 year period is roughly 10 times this, ie 10%.
  3. Almost by necessity each level of likelihood has a range, but placing boundaries may infer a reliability of prediction that is unwarranted for such crude estimates. The AGS is currently giving consideration as to where these boundaries should be.
  4. From an engineering/geotechnical perspective, the emphasis would be placed on the risk, rather than the likelihood. From a risk point of view size is important. The consequences of the reactivation of a slide the size of Slide B, which is probably upwards of 500,000m3, is vastly different to the reactivation of a slide of 5000m3 or 50m3. The proximity of the northern section of Slide B to the Dublin Town Road is also something that would be considered in assessing consequence.
  5. Ref 13 links risk category for debris flows in the Montrose area of Victoria with a 50 year probability of occurrence as shown in the table below. Note that a probability of occurrence as low as 0.5% is considered to be a medium risk. McIntosh & Weldon concluded that Slide B is a debris flow but, as discussed in the following, I doubt this conclusion.
Risk Category Assumed Probability of Occurrence
(50 year period)
High 5% - 39%
Medium 0.5% - 5%
Low Less than 0.5%
Very Low Less than 0.05%

My 'gut' feeling was that the probability of reactivation of Slide B lay between about 5 and 20%, based on the assumption that it was 'likely' to occur following an extreme rainfall event (1 in 50 to a 1 in 200 year rainfall event) during the 10 year period of increased water yield. This estimate was influenced by the occurrence of the four major local landslides reported earlier.

In my opinion, a probability of a slide in the order of 1 or 2% would seem to be 'real, and not remote'. However, I would caution that an approach based on estimates of probability is far too subjective and is unlikely to reduce disputes. Improved certainty will only be achieved by providing a sound and logical framework for investigations, recording and review. These matters are discussed in the following.

The degree of certainty that can be stated about a possible occurrence will usually be very dependent on the breadth and reliability of the available information. Where the information base is poor, uncertainty creeps in. Events that could otherwise have been classified as 'likely' or 'unlikely' had there been adequate information end up in a 'possible' bin. Uncertainty about the elevation of the Jubilee Mine workings was one of two factors that led to the abandonment of the proceeding.

Adequacy of and Responsibility for Investigations

In my view, the forestry proponent (in this case, Forestry Tasmania) should bear the responsibility for demonstrating that its operations will not cause environmental harm as a prerequisite for certification. Forestry Tasmania has not demonstrated this or provided evidence that would support its case.

Requiring the applicants to show that the proposed forestry operations are likely to cause instability removes any obligation from Forestry Tasmania to demonstrate with objective evidence that the forestry operations are unlikely to cause instability. Indeed it could be thought that in matters of potential dispute, it would not be in the interests of Forestry Tasmania to record baseline data. By and large this is what has happened.

Forestry Tasmania should have carried out an initial baseline survey and:

If Forestry Tasmania experts were faithful to their belief that removal of trees is safe on an inactive landslide, they should have undertaken the necessary studies that might demonstrate inactivity. The starting point should include:

The extent of their mapping is displayed in Attachment 2 (Figure 10 of Ref 1). No natural scale sections have been provided. This remains the case at April 2006.

In his latest report (Ref 15), provided with the Minister's reply to me of March 23, Dr McIntosh states 'On 8 February I took the opportunity of mapping the limits of landslide B in greater detail ... using a 1:10,000 base map'. The map provided in the report is at 1:15000 approximately. The area of Slide B on the map is less than the area of a One Dollar coin and no sections were provided. In consequence it is not possible to assess the reliability of his opinion.

It is likely that a landslide the size of Slide B will no longer move as a single unit and that there will be a range of activity states within the slide. Inactivity at the head is no assurance that there is no movement at the toe. It is therefore important to systematically map each and every part of the slide. I appreciate that systematic and comprehensive mapping of the slide and its environs would be an arduous and costly task because of very difficult mobility on foot away from the road. However detailed mapping is essential if the decision is to be based on activity. Exclusion of the slide and its surrounds makes a lot more sense.

The probability of reactivation of a landslide is dependent on changes to groundwater levels. In regard to this, and probably because of the emphasis that I had placed on groundwater level changes, Forestry Tasmania's experts argued (Ref 1) that I had failed to 'demonstrate that a significant groundwater aquifer exists'. In my view, it is clearly their responsibility, as proponents of the action, to determine the extent of groundwater aquifers below proposed harvesting activities. Furthermore, evidence of a high ground water level had been recorded by them in the seepage from the 1984/85 landslide. In Nov 2005 this seepage was evident at about 8 to 10m above road level

Personally, I do not favour going down the road of detailed investigations such as those outlined above. Such investigations will not achieve an appropriate degree of certainty and would not be worth the expense. Detailed investigations may be worthwhile where the potential benefits are large, say where avoidance might involve a significant increase in the length of a major road. In such situations attempts would also be made to increase the factor of safety by at least 20% through earthworks and drainage. However, in the situation of South Sister, the profit gained in recovered timber is likely to be small compared to investigation costs. The better course is to avoid the terrain where the instability has occurred.

Supplementary Proof of Evidence of Dr McIntosh and Mr Weldon

This evidence (Ref 1), provided on 28 September 2005, only a few days prior to the intended date of the Tribunal hearing, was confined to the locality of Slide B. It was not possible at that time to verify its accuracy.

The major issue with this document is the location of the 'road batter collapse'. The location of this feature was included in Fig 10 (Attachment 2). Attachment 3 shows this feature in its correct location and its relationship to other features.

The 'road batter collapse' is in fact a medium sizes landslide. It is probably 5 or more times as long as the obliterated road batter. Attachment 4 provides sketch plans and elevations and descriptions of surface samples taken from the base of the scar. Attachment 5 is a photograph of exposed coal and siltstone beds, exposed about 2m above Dublin Town Road.

The landslide is reputed to have occurred in 1984/85 and to have blocked the road for several days. The scar of the slide is still evident in air photos taken in 2000. What remains on the ground is a steep sided hole about 20m wide at road level, tapering to 4 to 5m at its head (which is about 45m slope distance) from the road. The depth of the hole ranges from about 1m to slightly above 2m. Water is seeping from the scar at about 8 to 10m above road level. The volume was quite small in November 05, but the amount appeared to increase at lower elevations.

As shown in Attachment 2 (Fig 10 of their report), this feature is indicated to be north of Slide B. They have positioned the 'road batter collapse' about 160m from the loading bay which puts it outside of the toe of Slide B, when in fact this feature is less than 80m from the loading bay and well within the toe of Slide B (see Attachment 3).

It is difficult to understand how two experienced investigators could so badly mislocate such a significant feature as the 1984/85 landslide. Its position is critical with respect to the geometry and composition of the slide, and possibly to its actual activity. It also provides the best exposure of strata within the vicinity of Slide B and for this reason alone, it would have been a feature of interest to them.

The location of this feature within the toe of Slide B puts an entirely different light on the nature of the slide and materials within it, its potential activity, volume of the slide compared to the picture provided in the report (Attachment 6):

Dr McIntosh (Ref 15) now recognizes that the 1984/85 slide was wrongly located in Attachment 2 but has made no amendment to the model of Slide B, portrayed in Attachment 6.

It was the reported presence of the massive sandstone high above the roadway as shown in their Figure 12 (Attachment 6), which is now known not to exist in that location, which effectively destroyed the hypothesis that Slide B was deep-seated. This hypothesis, which had been put forward by David Stapledon and supported by myself, appeared to be unsupportable in the light of the presence of the massive sandstone. It was also because their Figure 12 did not appear to be a truthful representation of conditions that I subsequently followed this matter up.

It is important to understand that new and unexpected information can take a considerable time to digest, much longer than the time that was available.

The authors did not provide any natural scale cross sections, though they did provide Attachment 6 (their Fig 12). It provides a rather perplexing picture of stratigraphy. Its vertical scale is not only exaggerated but it appears to be not to scale.

The upper surface of the slide is known to be at around RL 630 (the contours in Attachment 2 are 10m too low) and the road level is never greater than RL600. In consequence the height difference between these two points is around 30m. Using this height difference as the vertical scale, it would seem that the vertical profile upwards from the roadway comprises about 12 to 14 m or so of massive sandstone, 2 to 4m of siltstone/coal measures and about 12 to 14 m or so of landslide debris. However:

While the authors contend that the figure is only a sketch, it is difficult to understand why they did not try to provide a more accurate picture of conditions.

It seems as if McIntosh and Weldon are avoiding the very actions that the geotechnical profession generally accepts as essential in order to establish the risk of slope instability. Without accurately drawn natural scale cross sections and a very close examination and analysis of pre and post slide geometry, including considerations of statics and the balance of volumes lost at the head and gained at the toe of a slide, it would not be safe to assume the location of the toe or the thickness of the slide.

The authors concluded that 'the landslide is a debris flow formed in a dolerite talus deposits with a slip plane probably on or just above the underlying sedimentary rocks.'

I do not have any direct experience with debris flows, though I am acquainted with relevant reference material. On the basis of this information, I consider that Slide B is unlikely to be a debris flow. Debris flows are generally linear features that move considerable distances at quite high velocities.

The following extract from a fact sheet produced by the Shire of Yarra Ranges (Ref 13), describes a debris flow involving 30,000 cubic metres or earth and rock which occurred on the north-west slopes of Mt Dandenong on July 12, 1891.

'it continued down the mountain at a speed estimated to be up to 40km/hr ... flowed for up to two kilometres from the source landslip, with considerable damage being recorded over 1.4 kilometres ...'

If Slide B is in fact a debris flow, then it would be extremely unwise to disturb it in any way.

It is contended that I 'exaggerated the slide volume four fold'. This seems to be based on the assumption that the average slide depth was 5 metres, in contrast with my assumed average depth of 15-20 metres. They probably have overlooked the fact that 1m3 weighs about 2 tonnes. However, I do not entirely reject their hypothesis that Slide B is a debris flow about 5 m thick, but they have not produced any hard evidence to support this. In view of the extraordinary inaccuracies of their Figures 10 and 12, it would be remiss of me to just accept their opinion without such evidence.

Reponse to my Allegations of False and Misleading Information

I wrote to the Minister on 5 December 2005. The letter provided a background to the arguments about slope stability and my concerns about the location of the 'road batter collapse'. I argued that the Minister's acceptance of the evidence provided by Forestry's experts was not warranted when it can be shown that the evidence was both false and misleading. The letter included:

'I recommend that you take the following steps to address this issue:

  1. Satisfy yourself of the validity of my claim about the location of the 'road batter collapse'. This should be a simple matter of measuring the distance between the loading bay and the 'road batter collapse' and the distance between the 'road batter collapse' and the domestic water intake. It requires no more than a measuring tape and about an hour on-site.
  2. When you are satisfied as to the validity of my claim, take action to halt forestry operations on the coupe pending changes to the plan.
  3. Accept my recommendation that Zone E should be excluded from the harvestable area of the Coupe ...
  4. Investigate the failure of Forestry Tasmania's expert advisors to provide reliable information'

The Minister in his reply of 25 January admonished me for the use of 'misled' 'false and misleading information' and 'conned' and stated that the figure (Attachment 3) was just a sketch map resulting from a rapid inspection 'produced solely to show the broad relationship between the graben feature, the traces of the track leading northwards from it and the road batter collapse'.

The Minister's letter also stated that 'McIntosh and Weldon established that there is a definite toe on Slide B, well above the road', I presume from this rapid inspection. I could not reconcile this with the inaccuracies referred to above

To my way of thinking, if McIntosh and Weldon had done sufficient investigation to locate a definite toe to Slide B then they must have known the location of the 1984/85 landslide. On the other hand if they have not done sufficient investigation to fix the location of the 1984/85 landslide within ±10 to 20 m, then it seems that they had not done sufficient work to locate a definite toe.

In response, I wrote again to the Minister on 1 February 2006. The Minister, in the 25 January reply, had claimed that I had avoided certain matters, specifically Fig 11 and the 'graben' feature referred to in Ref 1. The background to this is that McIntosh and Weldon had claimed that a manmade pile of rocks was the 'graben' mentioned previously by myself and D Stapledon. The particular feature was nothing like a graben and was certainly not the feature referred to by either of us. In reply I tried to address the issues he had raised and stated 'The intention of my letter was to focus your attention to the false and misleading information, a matter central to the credibility of evidence'. In concluding I requested:

'I am not seeking an extensive reply from you. However, I would like answers to the following:

  1. Were the relative locations of the 1984/5 landslide and Slide B as shown in Fig 10 of McIntosh and Weldon's report incorrect?
  2. If so, an explanation as to how could two highly qualified and experienced professional officers could have undertaken the necessary exploration and mapping to locate the 'definite toe' of Slide B, but failed to locate the 1984/5 landslide feature which lies just below the toe?'

The Minister's reply of March 2006 did not refer to the above two matters, though the 1984/85 slide was correctly positioned in Fig 1 of the attached document (Ref 15). The Minister, in a reply to Dr F Daily dated 23 March 2006, had this to say:

'The allegations made by Mr Rallings of 'false and misleading' information have been thoroughly investigated and found to be misplaced. Dr Peter McIntosh has recently re-visited the coupe and his report shows very clearly that there is no evidence of recent land instability and that the proposed selective logging operations have negligible environmental risk'

I wonder who thoroughly investigated my allegations. Surely it was not Dr McIntosh?

Jubilee Mine

Attachment 7 shows the reputed location of the underground working with respect to Slides A and B. The mine entrance is at approx RL500. Item 8 in Attachment 1 is probably due to the collapse of the ground above into a total extraction area within the mine.

There have been various hypotheses about the impact of the forestry operations on the mine and vice versa. The trouble is that the elevation and slopes of the underground workings are not reliably known.

One theory is that the workings slope downwards, towards the south, and are at a relatively high level in the vicinity of Slide B. In consequence it is possible that Slide B may be well-drained and that any significant rise in groundwater is unlikely to occur as a result of forestry operations. There is anecdotal evidence supporting this view. However this drainage might not be effective at the northern end of Slide B because it is quite distant from the workings (Attachment 7).

Drainage to the south, if this is occurring, may cause a reduction in slope stability of the slopes below Zone S in the vicinity of the mine entrance. It is noted that an active slide (Ref 14 and Attachment 7) occurs near the mine entrance which is about150m above a famed valley. One local theory is that the mine is full of water. The possibility of a large underground storage in conjunction with the reported instability near the mine entrance should raise serious safety concerns that require close investigation. This matter has been brought to the Minister's attention.

Southern Facing Zone of the Coupe

The concern here has been about the impact of the forestry operations on terrain below the coupe and not of the effects within the coupe. The landslide-type feature within the proposed operations (Site 8 in Attachment 1 and 7) is likely to be the result of subsidence associated with the total extraction mining below and should be excluded from harvesting.

It was argued by Forestry Tasmania that harvesting operations in this zone were unlikely to impact on the lower slopes because, essentially, the additional water yield is unlikely to reach these slopes. I considered that this was not an unreasonable proposition, however there was little evidence presented to support the theory.

Believing that it makes good sense to err towards caution in the face of uncertainty and significant and untoward consequences, I suggested that it would be prudent to provide a buffer zone of about 200m along the proposed southern limit of the coupe. The proposed location and extent is shown in Attachment 1. The area involved is approximately 13ha. Its purpose was notional and aimed at soaking up lateral flows and also to provide some possible protection for the springs when water yields go into decline. I was also influenced by the thought that the cost of a buffer zone would be very minor compared to the rectification cost of any large-scale instability of the lower slopes.

Concluding Remarks

1. Process Related Matters

There seems to be an inappropriate and too close a relationship between Forestry Tasmania and the FPA. I say this because it appears that FPA staff played the central role in the slope stability investigations, yet these same staff were involved in the approval process and in the vetting of external comment and criticism of their work. This should not happen and to avoid such a conflict of interest it may be appropriate to establish a kind of 'firewall' between these two organisations with respect to the investigation and approval processes.

It seems to me that the FPA officer in this case failed to identify Slide B at the investigation stage and from that point on it has been a case of defending the 'indefensible'. However, the 'indefensible' is very well protected under current arrangements because:

I spelt out these concerns to the Minister in my letter of 5 December 2005. In his reply of 25 January 2006 he stated, 'I do not accept your assertions that there is a conflict of interest between Forestry Tasmania and the FPA. The FPA is constituted as a regulatory body quite independent from Forestry Tasmania. Its scientific staff have always worked independently when giving advice and making investigations.'

The system described above may not be serving Forestry Tasmania well. While it may well provide a barrier against objections, it is a recipe for hiding mistakes and inaccuracies. These, in turn, lead to public mistrust.

There needs to be changes to the Forest Practices Code to ensure that all existing landslides are excluded from forestry operations. The identification of a landslide should trigger an investigation of adjacent slopes. Adjacent slopes of similar geology, slope and aspect should be excluded. The Code should also deal with mines below coupes.

Minimum standards need to be set for geotechnical baseline studies and reports prepared for submission with the forest plan. The information should be of sufficient breadth and quality in order that an independent person, knowledgeable in the subject, could arrive at the same conclusion. Plans should not be accepted without this information.

2. Other Matters

I would like to think that government agencies and the persons responsible for their operation would not only always feel obliged to provide accurate and honest information, but would see any failure to do so as a serious matter and take action to correct the error. In the matter of the location of the 1984/85 slide, this has not happened. I must admit that it has left me with a considerable degree of mistrust.

In addition to the mislocation of the 1984/85 landslide there have been other significant errors. These include the initial failure to identify Slide B and the existence of the Jubilee Mine, and the failure to investigate recent history of large landslide within the Nicholas Range. These errors were essentially omissions and they probably arise from simple oversight and/or lack of system or attention to detail and there is no breach of trust in them. Some errors are almost inevitable in these matters because of haste and often because advisors work alone and without independent technical or editorial review of their work. The failure to give any serious consideration to the risks associated with a raised ground water table on slope stability (Ref 11) is a rather extraordinary omission.

I have not tried to make much of these omissions, though they should never have happened. Omissions, provided they do not involve the intentional with-holding of information, do not disadvantage other parties in the way that errors of fact can. In my view the mislocation of Slide B in Attachment 3 and the distorted cross section indicated in Attachment 5 amount to a serious breach of trust. They are presented as factual but they grossly misrepresent site conditions. To present such material as new and reliable evidence within a week of the hearing is very unfair. If Forestry and FPA do not approve of such information and actions then they should try to get to the cause.

In my view, Forestry Tasmania has yet to complete a baseline investigation appropriate for a site prone to landslide activity. So much effort and resources have been spent on disputation because of a lack of factual information. Had Forestry undertaken an adequate baseline investigation at the outset their costs would have been greatly reduced and most of the argument that has subsequently ensured may never had eventuated. Slide B would probably have been excluded. I believe that any delay or expense incurred by Forestry Tasmania should be attributed to the inadequacies in their early investigations.

I continue to believe that it is not wise to permit forestry operations within or adjacent to Slide B and recommend that the whole NE face of the coupe (see Attachment 1) be excluded from logging. This is not an assertion that Slide B is certain to be activated. Logging a slide is a poor risk with fairly incalculable consequences.


Attachment 1 - Figure 1 - David Stapledon (annotated by Ralph Rallings)

Attachment 2 - Figure 10 - McIntosh & Weldon

Attachment 3 - Figure 10 - McIntosh & Weldon (annotated by Ralph Rallings)

Attachment 4 - Plan, elevation of 1984/85 landslide with sample descriptions

Attachment 5 - Photograph showing exposure at road batter collapse

Attachment 6 - Figure 12 - McIntosh & Weldon (annotated by Ralph Rallings)

Attachment 7 - Reputed location of underground mine workings (annotated by Ralph Rallings)


1. McIntosh, P.D and B. Weldon. 2005. Supplementary Report on Soil and Land Stability Issues on Coupe NI114A and Surrounding Steeplands (27 September 2005).

2. Rallings, R. 2005. Proof of Evidence - An Examination of Slope Stability Issues associated with the Proposed Logging Coupe NI 114A at South Sister (May 2005)

3. Rallings, R. 2005. Supplementary Proof of Evidence (September 2005)

4. Australian Geomechanics Society Sub-Committee on Landslide Risk Management. 2000. 'Landslide Risk Management Concepts and Guidelines'. Australian Geomechanics, March 2000.

5. Lane, P. 2005. Scientific Review of Water Supply Impacts of Proposed Forestry Operations in State Forests Coupe NI114A at the South Sister, North of St Marys. Consultancy Report for Tasmanian Department of Primary Industry, Water and Environment.

6. Geoscience Australia and Emergency Management Australia. 2003. Landslide Awareness. Joint pamphlet regarding landslide risk and management.

7. Stapledon, D. 2005. Geological Studies Near South Sisters, Tasmania, Report prepared for Resource Management and Planning Appeal Tribunal Application A8/05

8. McIntosh, P.D. 28/11/2003. Comments on the report 'Appraisal of Initial Forest Plan on South Sister-Nicholas Range: hydrologic and landscape observations. D.E. Leaman, 22 Nov, 2003'.

9. Perera, A. Nov 1992. Landslip Susceptibility in Tasmanian Forests. A Report to the Forestry Commission.

10. Moon, A and R Wilson. 2004. 'Will It Happen? - Quantitative judgments of landslide likelihood' Proceedings of Australia New Zealand Conference on Geomechanics. University of Auckland: (2) 754-760.

11. Weldon, Barry. 2005. Proof of evidence (18 August 2005)

12. Weldon, B. 2005. Supplementary proof of evidence (September 2005)

13. Shire of Yarra Ranges (Building Services). Debri Flow Risk Areas: Special Considerations with Respect to Development in the Montrose Area. Fact sheet provided to residents.

14. McIntosh, Dr. P. 2005. Proof of evidence (including report on Land stability on Coupe NI114A and adjacent steeplands)

15. McIntosh,PD, 15 February 2006, Report on Further Fieldwork in the Northeastern part of Coupe NI114A

16. O'Loughlin, Dr.E.2005. Proof of Evidence (5 May 2005)


1 Lane (Ref 5) provided estimates of the expected change in water yield that would result from the proposed partial removal of trees from Coupe NI 114A. The water yield is the water available for surface and subsurface systems after evapo-transpiration. He estimated that this would rise by about 200mm immediately after logging and would then proceed to fall until the change went into the negative, about 10 years hence.

2 Risk is defined as 'A measure of the probability and severity of an adverse effect to health, property or the environment. Risk is often estimated by the product of probability x consequence ...' (AGS, 2000). The AGS document contains extensive advice as to the estimation of consequence with respect to human health and property, but provides no advice with respect to environmental consequences. There needs to be some 'yardstick' to gauge environmental consequences, and without such a measure it is difficult to express environmental risk.

3 The Forest Practices Code 2000 (page 53) provides that 'Areas with slopes greater than the threshold angle will be assessed for landslide hazard by a soils or other geotechnical specialist before operations can proceed'. However, in spite of locating Slide A, no investigation was carried out, presumably because the threshold angle of adjacent slopes was not exceeded. This matter needs to be addressed - the existence of a past landslide should trigger a hazard assessment of adjacent slopes, regardless of the slope angle. As discussed previously, a lower slope angle is not a safe indicator of improved stability (Ref 6).

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