Wagner & Ors v Harbour Radio Pty Ltd & Ors [2017] QSC 177

[2] The plaintiffs sue over 34 broadcasts and, necessarily, the imputations which are alleged to arise from each broadcast differ. The plaintiffs submit, however, that the essential sting of the defamations, as captured in numerous imputations, is that the plaintiffs caused the deaths of 12 people, or caused the flood which killed 12 people, when a quarry wall (the terms "embankment", "bund" and "levee" are also used) breached or burst or collapsed. It is unnecessary for the purpose of this decision to set out the imputations. The defendants do not contest what the plaintiffs submit is the essential sting of the alleged defamations, as pleaded. They do not accept that those meanings were in fact conveyed.

[3] A defence of truth must be directed towards justifying the substantial truth of the imputations pleaded by a plaintiff.

[4] The plaintiffs' position is that, having regard to the real issues in dispute, the appropriate issues to which expert opinion is to be directed are:

1. whether the existence or breach of the Grantham Quarry embankment caused or contributed to the flooding of Grantham; and
2. whether the existence or breach of the Grantham Quarry embankment had a material impact on the damage caused by the flooding at Grantham.

[5] The defendants have proposed that the experts be asked a series of questions.

[6] Having been unable to agree upon the issues to which expert evidence is to be directed, the parties sought leave to make written submissions so that the matter can be resolved, and requested that I consider addressing the matter "on the papers". I am prepared to do so and treat the present matter as, in effect, a joint application for directions.

[7] In earlier applications about earlier versions of the pleadings, I was concerned with aspects of paragraph 1(h) of the particulars of truth as they appeared in the amended defence filed 1 November 2016. That subparagraph relevantly stated:

"during the course of the major rain event that occurred on 10 January 2011 floodwater moving downstream in Lockyer Creek that had breached the natural bank of the creek at the point where it forms a horse-shoe around the Quarry, was prevented by the levee from flowing around, into or through the Quarry and was backed up behind the levee until such time as, owing to its inability to withstand the weight and force of the water so built up, at or about 3.45 pm, the levee suffered rapid breach in four places along its length, immediately releasing a torrent of water downstream towards the township of Grantham, causing a surge in the height (of between 1 and 2 metres) and velocity of the existing floodwaters, resulting in the rapid destruction or inundation of buildings in its path that would not have occurred but for the existence of and then breach of the levee, and in consequence the deaths of 12 residents who were trapped in, or washed from homes or vehicles or were otherwise caught in the path of the surge or during their attempts to escape from it".

[8] On 1 February 2017 I ordered the defendants to:

"(a) provide further and better particulars of the allegations contained in paragraph 1(h) of Attachment A to the amended defence filed 1 November 2016 ("the amended defence") including further and better particulars of:

(i) how the release of water after the levee was breached caused water levels to rise in the township of Grantham, including the course or courses the water took and the existence of intervening terrain, topography and water courses between the levee and the township of Grantham;

(ii) the facts, matters and circumstances relied upon in support of the allegation that the rapid destruction or inundation of buildings in the path of the water would not have occurred but for the existence of and the then breach of the levee, including particulars of the course such water would have taken in that event and the height of floods in and around the town of Grantham had:

[9] The further amended defence filed 28 February 2017 contained essentially the same allegations to the effect that "the collapse of the levee" led to a surge in the floodwaters and the consequent loss of 12 lives. The slightly amended particulars in sub-paragraph 1(h) read:

"during the course of the major rain event that occurred on 10 January 2011 floodwater moving downstream in Lockyer Creek that had breached the natural bank of the creek at the point where it forms a horse-shoe around the Quarry, was prevented by the levee from flowing around, into or through the Quarry and was backed up behind the levee until such time as, owing to its inability to withstand the weight and force of the water so built up, at or about 3:45 4.00pm, the levee suffered rapid breach in around two to four places along its length, immediately releasing a torrent of water downstream towards the township of Grantham, causing a surge in the height (of between 1 and 2 metres), mass and velocity of the existing floodwaters, resulting in the rapid destruction or inundation of buildings objects in its path that would not have occurred but for the existence of and then breach of the levee, and in consequence the deaths of 12 people residents who were trapped in, or washed from homes or vehicles or were otherwise caught in the path of the surge or during their attempts to escape from it".

[10] I am informed that the particulars which I ordered were provided separately to the further amended defence, and included diagrammatic representation of the general topography and course of the water, including in the alternative scenarios of the levee not existing, and the levee not being breached.

The issues and assumptions proposed by the plaintiffs

[11] As noted, the plaintiffs propose two issues for the experts to address. They are:

1. whether the existence or breach of the Grantham Quarry embankment caused or contributed to the flooding of Grantham; and
2. whether the existence or breach of the Grantham Quarry embankment had a material impact on the damage caused by the flooding at Grantham.

[12] The plaintiffs' solicitors also proposed the following assumptions upon which the expert opinion was to be based:

"For the purpose of modelling the range of impact of the breach of the Grantham quarry embankment, assume the following different scenarios for when the quarry embankment started to erode and how long the process took:

• Pre-quarry - as if the quarry pit did not exist;
• Early/Slow Breach - the breach started shortly after commencement of overtopping and the embankment took about 15 to 20 minutes to erode;
• Late/Slow Breach - the breach started slightly later in the flood and eroded completely within 1 minute; and
• No Breach - the quarry embankment remained fully intact throughout the flood.

Any other assumptions it is necessary for an expert to make for the purpose of expressing an opinion are to be identified in the expert's report."

[13] The defendants advance the following concerns about the plaintiffs' proposal:

"(a) the 'no quarry pit' scenario is foreign to the case on the pleadings. There always was a quarry in place, and there is no suggestion that it was the mere construction of the quarry that caused the problem. The issue is with the embankment;

(b) the 'caused/contributed to' dichotomy is apt to confuse and the answer provided may make the evidence difficult to utilise in front of the jury, if it does not squarely address the factual or legal questions posed by the defence;

(c) 'material impact' too raises the potential for ambiguous, or inapplicable answers;

(d) equally, no assistance is provided by the general term 'damage caused by the flooding';

(e) the issue is not with the 'flooding of Grantham', but the addition (sic) impact upon the flood event by the collapse of the levee - hence the requirement for the defendants to address allegations of an increase in rate, height and velocity of the floodwaters;

(f) the issues as framed by the plaintiffs lack the focus and specificity to provide useful answers."

[14] In response, the plaintiffs are content to exclude the "no quarry pit" scenario. The plaintiffs also submit:

"(a) The caused/contributed to dichotomy is consistent with the sting of the imputations, and therefore is not apt to confuse. If there is potential for confusion between the two terms then further refinement is relatively straightforward: the issue can simply be confined to 'caused';

(b) The use of the words 'material impact' will not have the potential to raise ambiguous or inapplicable answers. At this stage, the matters are being formulated as 'issues', not questions. If an opinion is formed that the existence of the embankment and its breach had an impact on the damage caused by the flooding at Grantham then presumably the expert will be able to explain what the impact was (the damage being notorious);

(c) The defendants' proposition that 'the issue is not with the flooding of Grantham, but the addition (sic) impact upon the flood event by the collapse of the levee' is an issue of the defendants' creation. The sting of the imputations is that the quarry wall, embankment, bund or levee, caused the flood. The defendant's proposed issue - if they persist with it - can be adequately addressed by their expert(s) within the confines of the plaintiffs' proposed issues."

[15] More generally, the plaintiffs submit that the essential issues to which expert opinion evidence should be directed will properly reflect the sting of the imputations, namely whether the presence of the wall (embankment, bund or levee) caused the flood at Grantham and whether the wall had an impact on the damage caused and led to the loss of lives. The plaintiffs submit that the issue for the experts should be sufficiently general to allow them to perform the role of an expert, and should not be curtailed by a defence which has been crafted by lawyers. In short, the experts should not be confined to narrow issues appearing in particulars to the pleaded truth defence.

[16] In reply, the defendants submit that the plaintiffs' position places undue emphasis on the imputations whereas the issue to which the experts' evidence will be directed are whether the meanings are substantially true. The defendants bear the onus in that respect and have particularised the facts upon which they intend to discharge that onus. Therefore, it will be against the defendants' pleaded and particularised case that the evidence, including expert evidence, will be tested.

The issues and assumptions proposed by the defendants

[17] The defendants' solicitors framed certain questions in correspondence:

"1. Initially, the experts are to agree on the observed hydraulic and hydrological phenomena from Helidon to Grantham which are relevant to the determination of their opinions. Thereafter they should assess the following questions.

1. Whether embankment(s) at the quarry prevented the flow of floodwaters downstream.
2. Whether, at or around 4pm on 10 January 2011, one or more breaches of the embankment(s) caused a sudden release of floodwaters.
3. If so, whether there was an increase in the rate of rise of, height of, or velocity of the floodwaters between the quarry and the township of Grantham, and if so, to what degree and in what direction(s).
4. Having regard to the answers given above, was the breach of the embankment(s) a cause of the destruction to property and the loss of life that occurred in Grantham.
5. What scenario(s) would most likely have eventuated at around and following 4pm on 10 January 2011 had the embankment(s) not breached, and had it/they not been there."

The defendants' solicitors accept that some minor modifications may be required to these questions so as to ensure that they appropriately engage opinions that can be given. However, further discussion about the refinement of these questions has not occurred because the parties have been unable to agree over the substance of the questions and the assumptions upon which they are made.

[18] The plaintiffs have contended that the defendants' proposed issues suffer from various problems, which include:

• (a) Paragraph 1 is too proscriptive and has the potential to usurp the experts' independent role, particularly in circumstances where existing orders provide for the experts to confer to address issues of methodology, analysis and opinion;
• (b) The fact that there is no meaningful connection between "questions" 2, 3, 4 and 6;
• (c) The proposed questions or issues raise false issues. For example, if the experts answered "yes" to issue/question 3 a jury may well be misled in considering whether the imputations are substantially true irrespective of the experts' answers to the other issues/questions posed;
• (d) There is no causal connection between proposed issues/questions 3 and 4; the use of the term "if so" begs the question whether there was in fact any link between a sudden release of floodwaters (issue/question 3) and "an increase in the rate, height of or velocity of" the floodwaters (issue/question 4).

[19] In reply, the defendants submit that each question posed by them responds to an issue, and that there is much to be gained in any event by ensuring the experts concerned are given focus and direction in the task they are to be given. The defendants also note that if the complaint noted as (c) above has merit, it can be overcome by appropriate directions being given to the jury. The defendants note that if the complaint noted as (c) above has merit, it can be overcome by appropriate directions being given to the jury.

The purpose of identifying the issues to which expert opinion is to be directed

[20] Any observations or directions I make on this matter are to assist the parties to formulate issues which their respective experts will address. The earlier direction which I made for the parties to attempt to agree on the issues to which expert opinion is to be directed is a common order made in the context of case management. It is intended to avoid the problems which arises when Expert A does not address certain issues which Expert B is asked to address by another party. Having respective experts address different issues tends to increase costs and delay. The opinions of experts, and their expert reports, are like ships passing in the night. Having experts address the same issues avoids the problems associated with Expert A not being required to address certain issues formulated by the other party until trial, sometimes in the course of cross-examination, at which point it sometimes emerges that Expert A and Expert B agree on certain issues.

[21] Having experts in the same field address agreed issues does not prevent a party from asking an expert briefed by it to address additional issues, if this proves necessary. It does not prevent a party from cross-examining the other side's expert about issues which have not been agreed between the parties, being issues to which expert opinion may be directed. Whilst these courses remain open to the parties, the costs associated with them should be avoided, if possible, by having experts in the same field address the same issues.

[22] Having the parties agree, if possible, on the issues to which expert opinion is to be directed also seeks to avoid problems which may arise at trial if an expert has been asked to address a false issue or non-issue, sometimes at great cost, with the result that substantial parts of an expert report are unnecessary or ruled inadmissible.

[23] The duty of an expert is to assist the Court in carrying out its duty, irrespective of by which party the experts has been engaged.[1] The Court's duty is to determine the real issues in dispute expeditiously and at a minimum of expense.

[24] The parties' differing formulation of the issues to which expert opinion should be directed, and their submissions, may appear to present the Court with a choice between having experts in the same field address a very general question or a series of specific questions. However, there is nothing wrong in principle with having expert opinion directed to both a general issue and specific issues, provided they are relevant issues to which expert opinion might appropriately be given.

[25] It is essential to recall that the determination of whether the embankment and its alleged breach led to the deaths of 12 people, as outlined in the particulars to the defendants' pleading, is a matter for the tribunal of fact, not the experts, to decide. Still, the tribunal of fact at the trial will be assisted by expert evidence in determining that issue. If the experts are asked a general question, of the kind proposed by the plaintiffs, then any evidence they give in addressing that issue and advancing an expert opinion will need to comply with the rules of evidence, including exposing the process of reasoning and the facts and assumptions upon which any opinion is based. In answering a general question an expert may address a series of subsidiary issues which explain the experts' process of reasoning.

[26] Accordingly, I see no objection in principle to the experts being asked to address one or two general questions, appropriately formulated, which are broadly reflective of the sting of the imputations and the essence of the defences of truth which rest on the general proposition that the collapse of the embankment led to a surge in the floodwaters and the loss of 12 lives. Nor do I see any objection to the experts being asked to address more specific questions which reflect the essential components of paragraph 1(h) of the defendants' particulars of truth. This is because, as the defendants' submissions note, it is for the defendants to prove their truth defence, as particularised. Accordingly, it is appropriate that expert opinion be directed, to the extent that admissible evidence may be given by an expert, to the general issue raised by the truth pleas and the components of paragraph 1(h) of the relevant particulars.

Distillation of the imputations and the truth pleas

[27] In formulating issues to which expert opinion is to be directed, the parties have sensibly avoided generating a multiplicity of questions based upon the truth of specific imputations. However, each publication is different, as are the imputations which must be defended. For example, Imputation 18(a) requires the defendants to prove the substantial truth of an imputation to the effect that the plaintiffs caused the death of 12 people when the embankment "burst in two places, resulting in lethal waves of millions of tons of water flooding into and devastating the rural town of Grantham". Imputation 71(b) requires the plaintiffs to prove the substantial truth of the imputation that the embankment "burst and caused a tsunami which killed people in the Grantham flood disaster". Imputation 83(a) requires the defendants to prove that the embankment burst "causing a wall of water to surge through Grantham". These are a few examples.

[28] The present point is that it may be convenient for the experts to address the nature and extent of any "surge" in the floodwaters which caused devastation and loss of lives in Grantham. Their evidence will allow the tribunal of fact to decide whether there was "a surge in the floodwaters" (to quote paragraph 141(a)(iv) in relation to Imputation 15(b)) or "a significant surge in the downstream floodwaters" (to quote paragraph 141(a)(v)(2) in respect of certain meanings pleaded in paragraph 18 and other imputations). Ultimately, it will be for the tribunal of fact to determine, if the matters contained in particulars 1(h) are proved, whether they prove the substantial truth of specific imputations.

[29] I approach the matter on the basis that the defendants' plea about a significant surge in the floodwaters, as particularised, concerns a surge that was experienced in the town of Grantham which resulted in the rapid destruction or inundation of objects, including buildings in its path, and which caused the death of 12 people who were trapped in, or washed from homes or vehicles, or otherwise caught in the path of the surge.

[30] It is important for the parties and the Court to address at this stage, lest there be any misunderstanding, the point raised in the defendants' submissions that the issue is not with the "flooding of Grantham", but the additional impact upon the flood event by the collapse of the levee. The plaintiffs contend that the sting of the imputations is that the embankment "caused the flood". That is not quite right, or at least is not clear. The sting of the imputations is that the embankment and its breach caused a particular kind of flood (variously described as a "lethal wave", a "tsunami" or a "wall of water"). The imputations do not suggest that the town of Grantham was otherwise unaffected by flooding when this distinct event occurred.

[31] As I apprehended it, the plaintiffs' imputations are not to the general effect that a breach in the embankment caused flooding in the town of Grantham. It seems to be assumed in the plaintiffs' reply that Grantham was the subject of flooding, irrespective of the operation or breach of the embankment. I apprehend that the sting of the imputations is not about the flooding of Grantham, or even, in a general sense, the role which the embankment played. It is more about the additional effect of the release of waters contained by the embankment upon flooding in the town of Grantham, and specifically at the locations in which 12 people died. More precisely, it is whether the additional effect was in the form of a significant surge in existing floodwaters.

[32] As I understand the defendants' pleading, they appreciate that it is not sufficient for them to prove that the release of water after the embankment was breached led to a steady increase in the height of existing flooding in the town of Grantham. In seeking to prove the substantial truth of a variety of imputations of which I have given three examples, the defendants seek to prove that objects in the path of the waters that were released as a result of a rapid breach were rapidly destroyed or inundated by "a surge in the height (of between one and two metres), mass and velocity of the existing floodwaters".

[33] This is the essence of the truth defence and the principal matter to which expert opinion should be directed.

[34] The relevant area of expert opinion is hydrology. The expert opinion depends upon assumptions being made by the experts about the alleged breach in the embankment, and the nature and timing of that breach being proven by the defendants in evidence.

[35] I am not familiar with the anticipated lay evidence to be called by the parties or the factual assumptions which hydrologists will be asked to make in formulating expert opinions. I should note that I have not read any reports of the Commission of Inquiry into the Grantham floods. Any such findings do not bind the tribunal of fact in this case. In any event, I have only a general recollection of some media coverage that occurred when the Commission of Inquiry into the Grantham floods released its report.

[36] If the parties wish, I will read a précis of evidence of anticipated lay witnesses to better understand the anticipated state of the evidence from lay witnesses in this case about the nature and timing of the breach of the embankment. Presently I proceed on the basis of the pleadings. As noted, the defendants propose to prove that the embankment suffered a rapid breach in around two to four places along its length at or about 4.00 pm, releasing a torrent of water downstream.

[37] In reply, the plaintiffs plead that the true facts are that the breach of the embankment did not lead to a surge in the floodwaters, and in consequence the loss of lives because:

1. The collapse or failure of the quarry embankment resulted in water filling a quarry pit situated next to the quarry embankment;
2. The quarry pit absorbed floodwater and in fact operated to delay the flood;
3. The water that engulfed the town of Grantham on 10 January 2011 would have occurred regardless of the existence of the quarry or the quarry embankment by reason of the sheer magnitude of the water which fell on that day;
4. The collapse or breach or erosion of the quarry embankment did not cause or materially contribute to the flooding of Grantham; and
5. The existence of the quarry embankment did not have a material impact on the damage caused by the flooding at Grantham and did not cause the loss of lives.

[38] The plaintiffs' further amended reply filed 21 March 2017 does not particularise whether the breach in the quarry embankment occurred at or about 4.00 pm, or whether the breach was a rapid one in around two to four places along its length. However, I apprehend from the assumptions which the plaintiffs propose for the purpose of expert opinion that different scenarios are contemplated including:

• Early/Slow Breach - the breach started shortly after commencement of overtopping and the embankment took about 15 to 20 minutes to erode;
• Late/Slow Breach - the breach started slightly later in the flood and eroded completely within 1 minute.

[39] If, as I apprehended, the parties do not agree about the nature and timing of the breach or breaches in the embankment, then it will be necessary for the relevant experts to give opinions based upon different scenarios. Subject to further submissions and assistance about what the evidence is expected to be concerning the process and timing of breach, it seems appropriate that the experts address the matter on the basis of different scenarios.

[40] Ideally, experts would express their final opinions after the relevant lay evidence is given at trial, and it may prove necessary for the experts to revise any opinion given in a report in the light of evidence which emerges at the trial. However, it will assist pre-trial preparation and the resolution of the matter if experts consider issues which are the proper subject for their expert opinion on the basis of either agreed facts (to the extent the facts can be agreed by the parties) or on the basis of different factual scenarios.

Is it an agreed or disputed fact that at around 4.00 pm on 10 January 2011 one or more breaches of the embankment caused a sudden release of floodwaters?

[41] The defendants' proposed questions would have the experts decide this issue. If the matter is agreed then it would seem to be unnecessary to have experts address it. However, I apprehend that this matter is not agreed and that the process and timing of breach is a disputed question of fact.

[42] Presently I doubt whether the defendants' proposed question 3 is a proper subject for expert opinion by a hydrologist. It may be an opinion about which a hydrologist or some other expert could venture an opinion based upon a review of witness statements, photographs, video recordings and other evidence. However, it would not necessarily be a matter about which admissible expert opinion could be given.

[43] In the circumstances, it seems appropriate for the contemplated experts to be asked to make an assumption about this matter. The question of whether the expert could give evidence about whether he or she agreed with the assumption can be deferred.

[44] My present view is that it is for the defendants to prove (unless it is agreed) that at about 4.00 pm the embankment suffered rapid breach in around two to four places along its length, releasing a torrent of water downstream.

[45] The experts may be asked to express opinions about various matters based upon the assumption that the defendants will be able to prove that essential element of their pleaded defence.

[46] I will hear the parties further as to the formulation of assumptions or scenarios of the kind proposed by the plaintiffs and any further assumption based upon the defence, as particularised, concerning the nature and timing of the breach.

[47] As to the plaintiffs' "No Breach" scenario, namely that the embankment remained fully intact throughout the flood, I am uncertain about the reason for including such a scenario, and will return to this topic later.

The matters to which expert opinion should be directed

[48] The purpose of the foreshadowed expert opinion is to enable the tribunal of fact to decide whether the defendants have established the substantial truth of a variety of imputations. It is to assist the tribunal of fact to make findings of fact. As earlier indicated, I see no objection in principle to the experts being asked one or two fairly general questions, and being required in accordance with the laws of evidence to explain the process of reasoning, including assumptions made, in reaching a particular opinion. In doing so, it is likely that any experts will formulate and address a number of subsidiary issues. In addition, and having regard to the manner in which the defence has been formulated, it seems appropriate for the experts to address certain issues which form part of that specific defence. The essential elements of that defence, as particularised in subparagraph 1(h), may be stated as follows:

1. The embankment caused floodwater to back up behind it;
2. The build-up of floodwater caused the embankment to suffer a rapid breach in around two to four places along its length at around 4.00 pm;
3. The breach or breaches released a torrent of water downstream towards the town of Grantham;
4. A surge in the height (of between one and two metres), mass and velocity of the existing floodwaters occurred;
5. This surge (and not some different and more graduated increase in the existing floodwaters) resulted in the rapid destruction or inundation of objects, including homes and vehicles, in its path resulting in the death of 12 people.

[49] Element 1 does not appear to be disputed. The second element seems to be disputed and issues seemingly arise as to the timing and process by which the embankment was breached, including when the breach started, the number of breaches and the period which it took for the embankment to erode. Similarly as to the third element, the manner in which water flowed after the embankment was breached appears to be in dispute. The fourth element would seem to be critical, particularly in the light of the reply which alleges that after the embankment failed, water filled a quarry pit next to the embankment and the quarry pit absorbed floodwater and delayed the flood. In any event, the existence and size of any "surge" after the waters left the vicinity of the quarry is in dispute. More importantly, whether the waters which were released produced a surge having a height of between one and two metres in the town of Grantham is in dispute. Finally, there seems no dispute that extreme flooding in the town of Grantham caused the death of 12 people.

[50] The formulation of any general question and any specific question is subject to appropriate definitions including the term "embankment" and "the town of Grantham". The problems of definition should not be ignored since views may differ about the boundaries of the town of Grantham. The expressions used in the parties' draft issues such as "the flooding of Grantham" or "the loss of life that occurred in Grantham" are used, as I understand it, to refer to a defined geographical location being the locations in which 12 people died as a result of the rapid destruction or inundation of objects, being trapped in or washed from homes or vehicles or otherwise being caught in the path of floodwaters. For present purposes I will use the expression "town of Grantham" to capture that geographical location. However, the matter may require more careful definition.

[51] Against the background of the issues which appear to be in dispute arising from the truth defences and the matters which would appear to be the appropriate subject of expert evidence from hydrologists or experts in similar fields, I venture for the consideration of the parties the following general issue:

"Did a breach or breaches in the embankment cause a surge of floodwaters of between one and two metres in the town of Grantham?"

"Did floodwaters released as a result of the rapid breach of the embankment add to existing floodwaters in the town of Grantham in the nature of a surge or wave of a height of between one and two metres?"

[52] In answering such a general question and to otherwise to assist the Court in resolving the issues which the Court is required to determine, any expert will be required to spell out the factual assumptions upon which any answer to such a general question is based. The assumptions would include assumptions or scenarios which the experts are specifically requested to make about matters such as breach. The experts should be instructed to specify the factual assumptions or matters of fact upon which any opinion is based including:

1. The respects in which the quarry embankment prevented the flow of floodwaters toward the town of Grantham;
2. Whether floodwaters overtopped the embankment;
3. Whether and when the embankment suffered a breach, including whether the embankment suffered:
   • (a) a rapid breach in around two to four places along its length; or
   • (b) some other form of breach.
4. The process by which the embankment eroded and the time it took for the embankment to erode;
5. The quantity of water released from the embankment:
   • (a) by any overtopping; and
   • (b) as a result of breach of the embankment.
6. The timing of the release of floodwater which breached the embankment;
7. Whether, and to what extent, the breach of the embankment resulted in water filling a quarry pit situated next to the embankment;
8. If so, whether the quarry pit absorbed floodwater and, if so, what effect that had upon the timing or extent of flooding in the town of Grantham;
9. The course which water released from the breach of the embankment took, and the existence of intervening terrain, topography and water courses between the embankment and the town of Grantham.
10. The height, mass and velocity of "existing floodwaters" at the relevant time and place;

11. The increase in the height, mass and velocity of existing floodwaters;

1. The mechanism or process by which waters released as a result of the rapid breach of the embankment added to existing floodwaters.

[53] The questions proposed above address, to some extent, questions of causation, namely whether the existence and then breach of the embankment "caused or materially contributed"[2] or simply caused (along with other causes) the rapid destruction or inundation of objects, including buildings and vehicles, in the town of Grantham and the deaths of 12 people. They do not necessarily address the issue of causation as that concept is known in the law. It is unnecessary to essay principles of causation or the fact that in some legal contexts the "but for" test is an inadequate test of causation. In the context of factual causation, something may be regarded as "a cause" of a consequence if it played a part, perhaps only a relatively minor part, in an outcome. In the present context, the existence and breach of the embankment may be said to have played a part in the flooding of Grantham. Both parties appear to accept that it did. The defendants' case is that it caused a surge in the existing floodwaters of between one and two metres to hit the town with devastating consequences. The plaintiffs' case in reply is that this did not occur and, in fact, after the embankment was breached the quarry pit operated to delay the flood.

[54] That said, proof of causation as an element of the defence would appear to require the defendants to prove that the existence and then breach of the embankment caused the rapid destruction and inundation of objects, including houses and vehicles, in Grantham, whereas such rapid destruction and inundation, and consequential deaths, would not have occurred but for the embankment's existence. Paragraph 1(h) of the particulars asserts this in its use of the words "but for".

[55] This aspect of causation is disputed by the plaintiffs who plead that the water that engulfed the town of Grantham would have occurred regardless of the existence of the quarry or the quarry embankment by reason of the sheer magnitude of the water which fell on that day.

[56] The tribunal of fact will be required to determine this causal question which might be formulated as follows:

"Did the existence of the embankment (and its breach) cause the rapid destruction or inundation of objects, including homes and vehicles, in the town of Grantham and the consequential deaths of 12 people?"

The "but for" aspect of the defendants' case poses the following question:

"But for the existence of and then breach of the embankment, would floodwaters have resulted in the rapid destruction and inundation of objects, including homes and vehicles, in the town of

Grantham and the consequential deaths of 12 people?"

[57] A related question which seems to be a subject about which expert opinion might be directed would be:

"If the embankment had not been constructed, and floodwater had not backed up behind it on 10 January 2011, would the flooding of the town of Grantham been substantially different?

If it would have been substantially different, then explain:

(a) The likely nature and extent of flooding that would have occurred in the town of Grantham;

(b) How the flooding would have been different in terms of timing, flood height, mass and velocity;

(c) The course or courses which floodwaters would have taken;

• (d) The effect of flooding on objects, including buildings and vehicles, in the town of Grantham;
• (e) Whether flooding would have resulted in the rapid destruction or inundation of those objects."

Such a question, or series of questions, seem appropriate to cover the "but for" construction and breach causation issue in the defence, and the response in the reply which I have noted in the third point in [37] above.

[58] The plaintiffs' proposed assumptions include a "no breach" scenario which asks the experts to assume that the embankment remained fully intact throughout the flood.

[59] I am not sure of the purpose of this assumption or scenario. It seems to be accepted that the embankment did in fact breach, although not necessarily in the manner particularised in paragraph 1(h) or at the time alleged.

[60] I do not rule out the possibility that this scenario may be relevant in some context. Some of the imputations relate to the construction of the embankment and whether it required and obtained necessary approvals. It may be that there is a scenario along the lines that if the construction of the embankment had been the subject of approval and been constructed in accordance with that approval, then the embankment, as constructed, would not have breached. However, as presently advised, this does not appear to be a real issue. If, however, it is then it may be necessary to include a "no breach" scenario and require experts to address the factual scenario of the embankment being constructed but not breaching. It may be that I made a wrong assumption and there is evidence available at trial that the embankment did not in fact breach. I seek the parties' clarification about the "no breach" scenario.

[61] Presently the relevant causal question centres on the existence of the embankment, as constructed. Some attention may need to be given to what assumptions experts are required to make about the presence of some form of pre-existing embankment or land form which did not require approval. The causal question may need to concentrate upon the embankment to the extent that it was constructed after a certain date without approval. In this sense the imputations and proof of their truth may focus upon an unapproved increase in the height of an embankment and not the complete embankment, as constructed. I have not addressed the issues of causation with an eye to such complexities.

[62] The essential causal issue which arises by reason of paragraph 141(a)(v)3[3] of the defence and subparagraph 1(h) of the particulars is the likely course of events had the embankment not been constructed. The issue concerns the past hypothetical fact of what would have occurred on 10 January 2011 if the embankment had not been constructed. This seems to be an appropriate matter for a separate specific question for suitably qualified experts.

[63] These reasons expose my present thinking about the parties' proposals about the issues to which expert opinion might be directed and the assumptions upon which the expert opinions might be based.

[64] The matter has been dealt with "on the papers" without a good understanding of certain matters of fact which may be the subject of evidence at the trial and the extent of agreement or disagreement between the parties on matters of fact, such as the timing and process by which the embankment was breached. Therefore I decline to make rulings about the final formulation of issues or assumptions. These reasons are sufficient to conclude that neither parties' formulations should be accepted. The parties are directed to confer prior to the pending review with a view to better formulating the issues to which expert opinion is to be directed and the assumptions upon which the expert opinion is to be based.

[65] The matter will be reviewed on 14 September 2017.

[1] Uniform Civil Procedure Rules 1999 (Qld) r 426.

[2] A term used in the further amended reply.

[3] This pleads that had the embankment not been constructed, there would not have been the surge in the floodwaters that resulted in the loss of lives.