IN THE MATTER OF The Resource Management Act 1991

Transcription

1 BEFORE THE NORTHLAND REGIONAL COUNCIL APP IN THE MATTER OF The Resource Management Act 1991 AND IN THE MATTER OF a resource consent application by The New Zealand Refining Company Ltd under section 88 of the Resource Management Act 1991 to deepen and realign the Whangarei Harbour entrance and approaches STATEMENT OF EVIDENCE OF SHAW MEAD (COASTALPROCESSES, NUMERICAL MODELLING AND MARINE ECOLOGY) Dated 21 February 2018 DIXON & CO LAWYERS PO Box Dominion Road Auckland 1446 Telephone: (09) Facsimile: (09) kelly@dixonandcolawyers.com

2 Introduction 1. My full name is Shaw Trevor Mead and I am an environmental scientist based at Raglan. 2. I hold BSc and MSc (Hons) degrees from the University of Auckland (School of Biological Sciences), and a PhD degree from the University of Waikato (Earth Sciences). 3. I am currently an environmental scientist and Managing Director at ecoast, which is a marine consulting and research organisation. I have over 20 years experience in marine research and consulting, I have authored/co-authored 53 peer-reviewed scientific papers, and have solely or jointly produced over 400 technical reports pertaining to coastal oceanography, marine ecology and aquaculture. I have undertaken over two thousand research and consulting SCUBA dives around the coast of New Zealand and overseas, and have led many comprehensive field investigations that have addressed metocean, biological and chemical components of the coastal environment. I am also a part-time lecturer (environmental change and coastal engineering) and research provider at Unitec. I am affiliated to the New Zealand Coastal Society (IPENZ) and am on the editorial board of the Journal of Coastal Conservation, Planning and Management. I am also technical advisor for the Surfbreak Protection Society (NZ) and Save the Waves Coalition, which mostly entails consideration of marine structures and developments and the impacts they will have or have had on high-quality surfing breaks. 4. I have a background in environmental science, coastal oceanography, numerical modelling, marine ecology and aquaculture. I studied for my MSc degree at the University of Auckland s Leigh Marine Laboratory, undertaking subtidal research there from 1994 to 1996 directed at the fertilisation success of sea urchins as a basis for the sustainable management and development of the commercial market. As part of my MSc degree in Environmental Science, I also completed a 4 th year law paper in Environmental Law focussed on the RMA (1991) (the subject of my dissertation was the quota management system law review which was under way at the time and ended in the Fisheries Act 1996). The marine ecological components of my Doctorate were directed towards subtidal habitat enhancement of marine structures/artificial reefs, while the 1

3 physical oceanography component was focussed on understanding the effects of coastal bathymetry on wave breaking characteristics using field measurements (bathymetry surveys, aerial photography and GPS positioning of in situ data collection) and hydrodynamic numerical modelling. More recently, I have been involved in a wide range of coastal consulting and research projects that have included the design of coastal structures and developments, and assessments and monitoring of physical and ecological effects of marine construction, coastal erosion control, marine reserves (annual monitoring of benthic communities, fish and lobster, inside and outside Goat Island and Hahei Marine Reserves for the past 10 years), dredging, outfalls, oil industry, aquaculture ventures and various other coastal and estuarine projects that have included hydrodynamic (waves and currents), sediment transport and dispersion modelling (including contaminants, suspended sediments, freshwater, hypersaline water, nutrients and petro-chemicals). 5. My experience in the expert areas of coastal processes, numerical modelling and marine ecology has been informed through my involvement with a range of projects in New Zealand and internationally that have addressed the design and impacts of ports and marinas, including capital and maintenance dredging and disposal. Relevant projects I have been involved with include; 5.1 Port Otago, NZ (capital and maintenance dredging disposal for entrance channel deepening); 5.2 Port Vinh Tanh, Vietnam (numerical modelling of dredging and disposal); 5.3 Port Gisborne, NZ (reclamation and re-alignment), Port Tauranga (maintenance dredging review) 5.4 Port Goodearth, India (numerical modelling of entrance dredging and breakwater construction) 5.5 Pine Harbour Marina, NZ (nearshore dredging disposal of contaminated spoil) 5.6 Port Nelson, NZ (numerical modelling of wharf area reclamation), Port Rokobili (reclamation and coastal hazard assessment) 5.7 Port Taranaki, NZ (tracer tracking for inshore dredge disposal); 2

4 5.8 Port Lyttleton, NZ (review of impacts of capital and maintenance dredging for harbour deepening); 5.9 Whangamata Marina, NZ (numerical modelling and impacts on ebb-tidal delta); 5.10 Port Denarau, Fiji (erosion control and flushing); 5.11 Centerport, NZ (impacts of harbour entrance deepening surfing amenity and coastal processes), and; 5.12 Auckland Future Ports Options Assessment, NZ (coastal processes and marine ecology). Code of conduct 6. I confirm that I have read the Code of Conduct for Expert Witnesses contained in the Environment Court Consolidated Practice Note I agree to comply with the Code of Conduct. In particular, unless I state otherwise, this evidence is within my area of expertise and I have not omitted to consider material facts known to me that might alter or detract from the opinions I express. Introduction 7. I was engaged by Patuharakeke Trust Board to review the relevant technical reports and evidence for the present application to deepen and realign the entrance to Whangarei Harbour. The Patuharakeke Trust Board s initial concerns were that there exists uncertainty as to whether this project will result in significant environmental harm and consequently undermine their efforts as Kaitiaki to take care of and restore these highly-valued coastal sites; their taonga. 8. I have reviewed the following documents in the preparation of this statement: 8.1 Richard Reinen-Hamill (applicant s evidence, dredge, disposal and coastal processes); 8.2 Dr Brian Coffey (applicant s evidence, marine ecology); 3

5 8.3 Dr Brett Beamsley (applicant s evidence, numerical modelling and physical environmental effects); 8.4 Volumes 1, 2 (parts 1-4) and 3 (parts 1-7, 9, 10) of the Application documents; 8.5 Tonkin and Taylor, Refining NZ, Marsden Point Site Stage 1: Geomorphology and Baseline Report; 8.6 Prof. Paul Kench (peer review of Coastal Processes Assessments and Effects); 8.7 Dr Rob Bell (peer reviews of coastal processes and dredging/disposal options, and numerical modelling predicted physical environmental effects); 8.8 Dr Drew Lohrer (peer review, marine ecology); 8.9 The relevant sections of the S42a Staff Report, and; Summary 8.10 A range of published literature pertaining to the impacts of harbour deepening. 9. After reviewing the above documents, I consider that the application is lacking the relevant information to adequately enable an understanding of the extent of the likely physical impacts and the implicit links between physical and biological processes. 10. I acknowledge that comprehensive field investigations, data review and numerical modelling have been undertaken. However, in my view this work has been done in relative isolation with respect to the known impacts of entrance channel deepening worldwide. 11. I do not accept that there will be no significant changes to waves (e.g. T&T, 2017 Executive Summary and section 5.1 Volume 3 part 10) and therefore sediment transport and geomorphology, or that the conclusions of insignificant and negligible impacts are in anyway supported because the predicted changes are within the limits of natural variability. Many large-scale 4

6 changes have been identified by the modelling that will impact on the form and function of the harbour entrance, this is supported by a range of international and national channel deepening projects, while the importance of the couplings between the physical and biological processes of the Mair Bank and ebb-tidal delta have been all but ignored. I expand on my concerns associated with potential impacts of the entrance channel realignment and deepening in the following sections. 12. In terms of the approach taken to modelling, while I agree that industrystandard models have been applied to the investigations 1, I note that the validation of the tidal current model is poor (Figure 4.4 volume 2 part 1), and I consider it is important to recognize that models are tools that should be used in conjunction with existing science and knowledge with regard to the particular location in question and the kind activity being undertaken. In this case it appears there is a reliance on the numerical models and tools that provide estimates, with little incorporation of science and site specific knowledge beyond them. 13. In the present case, many of the tools have been developed to determine the likely impacts of entrance channel deepening (and consequently develop methods to sustainably manage these impacts). However, although they have been applied in terms of considering the known impacts of channel deepening world-wide, there is a deficit of information linking to the strong biogenic influence in the system, as well as a confusion with respect to natural variability and a regime shift/permanent change. Effects of Entrance Channel Deepening 14. In my review I have focused on the morphological changes to the harbour entrance channel due to the removal of some 3.7M m 3 of material (deepening and re-alignment) which is a press impact; that is a permanent change/modification that will consequently cause changes to the wider environment, as is evident in the large spatial scale of the changes to 1 Noting that there is mostly reasonable validation of the models when compared to measured data. 5

7 hydrodynamics, waves and consequently sediment transport presented in the modelling reports. This permanent change to the entrance channel s depth and alignment will be maintained by regular maintenance dredging The estimated dredging and disposal volume and areas of disturbance are for the proposed entrance channel deepening campaign 3,700,000 m 3 and 1.44 km 2, respectively. This is a large dredge volume (Mr Reinen-Hamill, para 152), and consequently has the potential to have significant impacts on the existing morphodynamics of the harbour system as it exists today, which have not been well addressed. 16. The Whangarei Harbour, entrance channel and the various banks that it consists of is described as a natural sheltered, tidally dominated harbour system, and analysis of the entrance channel and bank system have been shown to be stable over the past 76 years (Volume 3, part 10). Deepening and realignment of the entrance channel through the removal and disposal of a large amount of material (3.7M m 3 of sediment) over a large area (1.44 km 2 ) will result in changes to this system. I consider that changes to hydrodynamics, waves and sediment transport over very large areas inside and outside the harbour, will not simply be absorbed by natural variability, especially given the sheltered and stable nature of the system (i.e. it is not a highly variable system). 17. One well known process that results in morphological changes to harbour systems through an increase in the tidal prism is an increase in channel crosssectional area at the throat of an estuary through dredging activities (O Brien, 1969; Powell et al., 2006; Rakhorst, 2007 cited Stive and Rakhorst, 2008) (Figure 1). In addition, tidal amplitude is increased (Healy, 2006) and depending on estuarine morphology, the respective timings of high and low tide can be altered; which is expected in Whangarei Harbour. A larger channel 2 I have not addressed the impacts of the dredge plumes that will be generated during the 6- month capital dredging programme to remove some 3.7M m 3 from the Whangarei Harbour entrance channel. This is because the material being dredged is relatively very clean material (i.e. has only a small amount of fine sediments), and because the plume impacts of the dredging campaign can be viewed as a prolonged pulse impact (i.e. it is not a permanent change/modification). 6

8 cross-sectional area can result in stronger or weaker tidal currents depending on the morphology of the estuary entrance. This is reflected in the stability relationship presented in Figure 4.3 of volume 3 part 10 (Figure 2). Figure 1. Throat inlet cross-section as a function of the tidal prism after Powel et al. (2006) 7

9 Figure 2. Stability of New Zealand tidal inlets using Heath (1975) relationship (Source: Hume and Herdendorf,1985b) (reproduced from Figure 4-3 Volume 3, part 10). Note, scale bars a logarithmic. 18. In the present case, a lobe of material representing some 593,900 m 3 is to be removed from the throat (a cross-sectional area of some 660 m 2 ) (Figure 3). As a result, there is expected to be a shift in the tidal phase/time (reported as 7 minutes), which would be driven by an increase in the tidal amplitude (i.e. lower low tides and higher high tides), which with reference to Figure 2 would likely increase the deposition within the harbour (this is in line with the work of Van der Wegen, 2013), which is presented in the T&T coastal processes report and discussed below in relation to Mair Bank). 19. I have reviewed the technical documents submitted in support of the application to determine the analysis of the tidal phase shift. However, I have not been able to locate any relevant discussion about phase shift but for the reference on page 53 (Volume 2 part 3) in the final dot point of the summary, which reads While the hydrodynamics of the internal harbour are not expected to be affected by the deepening, a very slight adjustment of the timing of the tidal phase may occur. This will likely require a period of measurement at the defined tidal stations to derive the new tidal constituents for Northport and Whangarei Port. and further discussion on the phase change by Dr Beamsley (paragraphs 234 to 237), which I discuss in the section on cumulative impacts below. There remains uncertainty as to how this tidal phase shift was determined, what the consequent tidal amplitude will be (i.e. the changes to the extents of high and low tide) and how it will impact on other areas of the harbour (rather than the single point location it has been derived from (Dr Beamley s evidence Figure 17)). 20. In my view, such changes to tidal amplitude and phases can have significant impacts on low gradient higher intertidal and shallow subtidal areas of the harbour (i.e. on a low gradient, even a few centimeters of vertical change can result in large changes in the horizontal plane). However, the investigations/modelling focus on the harbour entrance and open coast and do not present or consider results and impacts far into the harbour. Indeed, consideration of changes to the inner harbour are restricted to 2 sentences The inner harbour area extends into Whangarei Harbour westward of 8

10 Northport. Tidal flows are low and confined to the channels and waves tend to be locally generated within the harbour. (Section 5.5, Volume 3 part 10). Figure 3. The large lobe of sand to be removed from the throat of the harbour entrance is flanked by the large extent of the intertidal Mair Bank to the south and the shallow (<1 m deep) subtidal Calliope Bank to the north. 21. The fundamental laws of physics indicate that change will occur (a response/reaction to the action), and that in a coastal environment, even subtle changes can lead to relatively large change over time (e.g. Castelle et al. 2010, Murray and Ashton, 2001). A brief literature search provided a number of international examples of the hydrodynamics, waves and sediment transport changes that can occur when harbour entrance channels are deepened and realigned. It is noted each and every harbour system is unique, with a wide range of different forcing factors and mechanics, and that the following examples include situations where significantly lower and significantly higher volumes of material have been removed from the harbour entrance channels than in the present case (by orders of magnitude both smaller and larger). The point is to demonstrate that harbour entrance channel deepening has the potential to result in changes to the system; such as: 9

11 21.1 Increased erosion or deposition rates inside and outside the harbour; 21.2 Modifications of terrestrial habitats along coastal margins; 21.3 Changes to physical sediment transfer and natural features of the harbor; and 21.4 The biology and chemistry of the harbor itself. Essentially the entrance channel morphology is a key component of a harbour system and the effects of altering this entrance channel requires assessment of the likely and potential effects on the wider harbour. 22. For example, major channel deepening works in the approach to Harwich Harbour, UK, has altered the sediment transport regime (HR Wallingford & Posford Duviver Environment 1998). The capital dredge increased siltation in the harbour, which subsequently reduced the amounts of sediment input into the Stour/Orwell Estuaries and increased the requirement for maintenance dredging. The net effect was to increase mudflat and saltmarsh erosion in the estuaries, with adverse effects on intertidal morphology. In this case the capital dredge has created the conditions for increased erosion, which is sustained by the regular removal of sediment from the harbour for disposal at sea. 23. Changes to the bathymetry of Port Phillip Bay, Australia, resulting from the Channel Dredging Project (CDP), has led to effects on tidal levels and currents within the bay (Healy, 2006). Changes in the sub-marine cross-section of the Heads as a result of the CDP has altered the tidal variations at various points around the bay s perimeter. Similarly, the deepening of shipping channels within the bay has influenced tidally driven currents, and to some degree also wind-driven currents (PoMC, 2007). In the context of these hydrodynamic interactions of the CDP, three types of effects warrant attention: 23.1 Effects on terrestrial habitats and other coastal assets along the Bay s edges, including islands, due to changes in water levels; 23.2 Effects on existing patterns of sediment transport, due to changes in currents and waves; and 23.3 Effects on the physical-chemical environment of the Bay, due to changes in water exchange with Bass Strait. 10

12 24. The dredging activities in the Ribble Estuary, UK, led to accelerated accretion because of the concentration of ebb currents in the over-deepened navigation channel and the enhancement of the flood tidal component over the sandbanks flanking the main channel (van der Wal., et al., 2002). 25. Much of the accumulation of sediment in the upper estuary bays of the Columbia River Estuary, USA, is related to the displacement of sediments from the natural tidal delta as a result of the deepening of the entrance channel (Sherwood et al., 1990). Thus, constraining tidal currents and transporting sediment both offshore and into the estuary. Whereas the inner and outer tidal deltas were relatively close to each other, they are now separated by several miles of deep channel and by the spits formed around the training jetties. The inner tidal delta was a distinct, dynamic feature consisting of intertidal islands and shoals. The modern inner tidal delta has been forced further into the estuary and is no longer a distinct feature. The sandy sediment that made up the relict inner tidal delta is now found in Trestle Bay, Baker Bay, and Desdemona Sands. 26. The balance between landward retreat and seaward extension of inter-tidal flat and salt marsh fronts in the Westerschelde Estuary, Netherlands, is related to an increase in the tidal prism brought about by dredging operations to maintain or increase the channel depth (Cox et al., 2003). The consequent increase in the inundation frequency of the flats and marshes increases the risk of erosion. An elevation deficit is developed if the vertical accretion of the flat and marsh surface is not able to keep pace with the increase in associated high-tide levels. Additionally, the flat/marsh edge is more frequently vulnerable to scouring caused by increased tidal velocities as well as increased exposure to wave action. This has resulted in very little new salt marsh formation (lateral expansion). It is noted that this is an extreme case with 310M m 3 dredging in total over a 40 year period. 27. Mr Reinen-Hamill refers to Tauranga Harbour channel deepening in the introduction to his evidence, although does not discuss the impacts that it has had. Numerical simulations were used to support measured changes to the entrance channel and ebb-tidal delta (bathymetry surveys and nautical charts) which indicate that the 1968 channel deepening and widening of Tauranga Harbour significantly changed sedimentation patterns over the Matakana 11

13 Banks ebb-tidal delta, concentrating accumulation on the Matakana Island shoreface (which is connected to the ebb-tidal delta), and reducing sedimentation on the swash platform (Ramli, 2016). Dredging since 1968 has had two main direct effects on the morphology of the entrance: a shallow shelf of boulders has been largely removed, deepening the channel along the flanks of Mauao; and creating a deep channel through the Pleistocene ridge (de Lange et al., 2015). Indirect effects have included further accretion of Panepane Point, an increase in the offshore extent of the ebb tidal delta, and the development of multiple lines of swash bars on the swash platform (de Lange et al., 2015). It is notable that the combined widening and deepening volumes at Port Tauranga entrance channel is <300,000 m 3 (i.e. an order of magnitude less than proposed for Northland). 28. Port Otago channel deepening is another relevant New Zealand example. Single et al., (2010), originally concluded that the effects of the dredging operation on the physical coastal environment are considered to be minor. However, it was demonstrated not the case, and following an out of court settlement with the Surfbreak Protection Society (SPS), and 4-year temporary resource consent that included intense monitoring, cessation of new shore disposal at Aramoana and numerical modelling, the negative impacts of disposing too much material to the nearshore were proven. Subsequently, and more robust maintenance dredging and disposal management plan has been developed. 29. The impacts of maintenance dredging on the Whangamata Bar (ebb-tidal delta) are an example of how even small changes to the harbour channels can have large impacts on the system. In 2009, a marina was opened within the harbour. It has recently been found that the 4-6 month maintenance dredging of the Moana Anu Anu channel approximately 1 km inside the harbour entrance, has profound impacts on the ebb-tidal delta manifest as aggressive growth of the ebb-tidal spur and an offshore shift of the flood tidal channel (unpub. data). 30. These examples demonstrate the vast range of changes that occur when harbour channels are modified. The Whangarei Harbour and Heads are unique. Although modeling provides some understanding of potential impacts, the actual and likely impacts of the proposed dredging and disposal campaign will be unique to the physical and biological environment. Indeed, there are strong 12

14 couplings between the biological communities and physical processes that have not been considered in the application material and assessment of effects, which I address below. Modelled Impacts 31. As stated by Prof Kench, the main modelling report is a technically demanding one to navigate. Even so, the results of the modelling investigation present what I consider to be strong evidence of significant spatial change, which in some cases are also relatively large changes. For example, Dr Beamsley states (para 138) that on the eastern flank of the channel the potential sediment flux is predicted to increase by up to 20% for the majority of wave conditions likely to be experienced, which is >70% of the time. Similarly, changes in shear stress over large areas 3 of the site are predicted to change 20-30%, although these changes are dismissed by simple one-line statements such as Nevertheless, it may induce local adjustments with a relative low degree of significance for the overall system. Changes of 20-30% seem to be considered minor, while changes of +/- 5% are considered insignificant. I do not agree with this classification, the relative effect of changes should be related to impacts on the processes, not relative change, as discussed below. 32. Figure 4 presents Figure 6.13 (from volume 2 part 3) of a 28 day simulation, but only presents results above changes of +/-5%. Close inspection of Figure 6.12 (Figure 5 here) indicates significant changes to shear stress throughout the harbour, which are presumably all less than +/-5% changes. However, even small changes in sediment transport and consequently morphology over large areas have the potential to change large areas of the harbour. These impacts are shown for what occurs during a 28-day period. Note the duration of the change is not a 28-day period, it is permanent. With each small change providing the potential for feedback to cause further changes throughout the area. It is also notable that the areas of change to shear stress that can be determined from Figure 5 are consistent with sediment transport pathways 3 The size of the Figures in the reports should not be confused with the huge spatial extent of the activity or the potential impacts. 13

15 presented in Figure 4.19 volume 3 part 10 (Figure 6). These long-term changes have not been investigated adequately and remain unknown and unquantified. Figure 4. Reproduction of Figure 6.13 volume 2 part 3. Note the scale bars omit changes between +/-5%. 14

16 Figure 5. Reproduction of Figure 6.12 volume 2 part 3. Percentage of time the bed shear stress exceeds the critical shear stress threshold for 200 μm sand at flood tide. Calculated from a 28-day simulation of the existing harbour (Top) and the deepened channel (Bottom). 15

17 Figure 6. Reproduction of Figure 4-19 volume 3 part 10. Schematic diagram showing sediment transport pathways within Whangarei Harbour based on residual velocities (Source: Black et al., 1989). 33. Similar examples can be found throughout Mr Reinen-Hamill s and Dr Beamsley s evidence, where broad statements are repeated that acknowledge and point to a range of changes. However, they are dismissed as insignificant, negligible or minor, or even no change even though a change has been identified (e.g. the changes to the wave height on the ebb-tidal delta due to the capital dredge disposal mound). As pointed out by Prof. Kench, the modelling report stops short of assigning relative levels of significance to such changes, which are dealt with in the final Tonkin and Taylor analysis, although still not qualified or adequately quantified. 16

18 34. Dr Bell provides a useful example of the lack of quantification within the impact assessment. On wave effects from dredging (Exec Summary and section 5.1) the T&T report states that there will be no significant change to waves (either from the deepened channel or from mounds at disposal areas). Dr Bell questions For Mair Bank, while apparently stable, is there any likelihood of subtle changes occurring in the shallower morphology due to these more subtle, but permanent changes (reduction or increases) in waves rather than just making the observation that the changes are simply within natural interannual variability, so the effect is not significant. 35. Similarly, Dr Bell points out In Exec Summary under Combined Effects, the final sentence simply states there will be no changes to existing coastal processes what information was used to assert there would be absolutely no change? (See previous point about discussing subtle changes). Also in Section last sentence categorically states no effects, but is there a possibility there may be subtle effects? Ongoing monitoring of the volume of Mair Bank would cover any changes, if they did eventuate, but it is acknowledged that isolating minor or negligible effects from natural variability is a difficult task (but if an effect was realised, it could be rectified by adapting the disposal regime at Area 1-2). 36. It is my opinion that the modelling investigations show that there are a wide range of changes of varying magnitudes over a very large spatial extent; the Mair Bank is a case in point that is discussed below. Many of these changes have been dismissed because they are within the limits of natural variation of tides, waves, currents and sediment transport. However, this is a misconception, it is not the magnitude of change in comparison to natural variation, but rather the change within the bounds of natural variation that is important. If you change a major component to a system (e.g. deepen and widen the entrance channel to the harbour by the extraction of some 3.7M m 3 of material), there will be a fundamental change/shift to the system and the natural variability will fluctuate around a newly established norm. 37. Simple analogies to understand the difference between a fundamental change in the system and natural variability are considering the well-known bell-shaped curve of natural variation, and the impacts of subtle wave-climate changes on a pocket beach. It is recognised that there are various shaped distributions for 17

19 physical parameters, however, the bell-shaped curve can be considered a generalised representation. Figure 7 provides a graphical representation that shows how fundamental change in a system (e.g. deepen and widen the entrance channel to the harbour by the extraction of some 3.7M m 3 of material) will lead to a change in the norm (as is demonstrated by the modelling), which shifts the system and leads to changes, even though the magnitude of natural variation remains the same. The change(s) is far less than the limits of natural variability, but there is significant change to the system. Figure 7. A fundamental change in a system (e.g. deepen and widen the entrance channel to the harbour by the extraction of some 3.7M m 3 of material) will lead to a change in the norm (as is demonstrated by the modelling), which shifts the system and leads to changes, even though the magnitude of natural variation remains the same. 38. The pocket beach analogy is with respect to subtle changes in wave climate. For example, if the pocket beach (i.e. a beach held within headlands at either end that all but prevent sediment transport exchange out of the beach system alongshore) is considered on the eastern coast, when there are subtle changes to the wave climate in terms of direction, this will be manifest in changes to the erosion and accretion patterns within the embayment. For example, on the east coast of Australia, the El Nino pattern means slightly more southerly quarter wave events that result in erosion to the southern end of pocket beaches and accretion to the north (Ranasinghe et al., 2004). The opposite occurs when La Nina dominates and there are slightly more northern quarter events. The natural variability has not changed and is far greater than the 18

20 subtleties of El Nino versus La Nina wave climates, but the beach system undergoes significant change. 39. Changes to the Whangarei Harbour entrance system and harbour are presented in the modelling that are often manifest over very large areas, and sometimes of significant magnitude. These changes are not well quantified and are not considered over the long-term this is reflected in his general responses to submitters concerns; in my view they are not adequately addressed. As such, I consider that 20-30% change in bed shear stress is likely to be significant. I do not agree with the assessment in the officer s report that effects on inner harbour are expected to be negligible (paragraphs ), as there is no evidence to support this conclusion; large spatial changes have been identified within the harbour and impacts on the inner harbour have not been adequately assessed. Effects on Waves Due to Disposal Mounds 40. I hold concerns with the investigations and interpretations of the impacts on waves and consequently the coast with respect to the impacts of the disposal mounds. For example, Mr Reinen-Hamill states that there are no measurable effects of placing sand in the marine disposal area 3.2 in terms of coastal processes (para 145), and so no measures are proposed for this location. However, the modelling clearly demonstrates that there are impacts on wave heights (increases and decreases) over an area of 10 s of square kilometres (Section 4.2 volume 2 part 2), as shown in Figure In addition, while 5-10 cm change wave height may not sound like a large increase, in terms of wave energy reaching the coast, 10 cm/m of wave crest represents very large amounts of energy we are not considering a single wave 10 cm higher, it is all waves during an event. Offshore disposal is known to impact on the coast inshore (e.g. Olivera, 2006), due to both changes in wave height and direction. In the present case the large changes in wave have been again bundled in with natural variability, and wave directions, which have impacts on alongshore sediment transport flux, have not been considered at all. As Dr Bell pointed out, there will be a change; in order to adequately manage this impact it must first be properly understood. This is particularly important with regard to Mair Bank (i.e. the ebb-tidal delta), Marsden Bank and 19

21 the coast in this area, and the swash channel system, all of which are connected to the ebb-tidal delta. Figure 8. Figure 4.6 reproduced from volume 2 part 2. Average annual change in significant wave height due to the deepened channel. Positive amplitudes indicate areas with a predicted increase, negative areas a decrease. 42. Many to the conclusions drawn from the changes predicted by the numerical models in the technical reports are based on relative change (e.g. percentage difference) and natural variability. For example, Mr Reinen-Hamill s statement with regard to cumulative impacts (para 93) is that Overall the changes to tidal flows and wave conditions resulting from the channel dredging and marine disposal are small and typically within the existing variability of tidal currents and wave energy. (emphasis added). It is uncertain what the following sentence in paragraph 93 means No changes to existing coastal processes are anticipated to be negligible on the open coast from Marsden Point to Ruakaka River or along the rocky coast from Home Point to Smugglers Bay, on the ebb tide shoal and Mair Bank or within the inner harbour area. Although given the other conclusions that Mr Reinen-Hamill has arrived at (e.g. no change due to changes in wave heights), I assume that this sentence is meant to read that changes will be negligible so there will be no impacts. This is not demonstrated in the modelling results and cannot be supported by the known 20

22 impacts of similar entrance channel deepening projects (e.g. Tauranga Harbour). 43. It is not relevant to relate the predicted changes to the percentage or absolute change to a particular parameter (e.g. wave height, current speed, shear stress, etc.) when considering significance of impacts, they must be related to the physical processes that they have the potential to impact on. For example, what is the impact of an increase in current speeds of 0.1 m/s, what will happen in terms of sediment transport (mobilisation and deposition patterns) when shear stress changes by 30%? It does not matter how relative it is to the existing currents or existing shear stress, but how will the change be manifest in the particular coastal process. 44. These comparisons to relative change along with the comparisons to natural variability represent the major flaws in the interpretation of the modelling results. Therefore, while the models developed may be useful tools, in my opinion in much of the investigations presented they have not been appropriately applied or interpreted. This is supported by scientific accounts of the changes caused by harbour entrance channel deepening world-wide and in New Zealand. The dredging and marine disposal of 3.7M m 3 will have impacts on the Whangarei Harbour system, and these need to be better understood and quantified in order to sustainably manage these impacts rather than disregarded as individual components of change that are too small relatively to have any significant impacts. Impacts to Mair Bank 45. As noted in the officer s report, the predominant issues of concern are around localised effects on hydrodynamics, particularly in regard to the ebb tide delta and Mair Bank. The ebb-tidal delta is an important stabilising feature of the harbour entrance. As noted in volume 3 part 10, stability of the harbour entrance has also been attributed to the presence of shell material, which provides an armour layer protecting the underlying soft sands and influences the long-term stability of the ebb tide delta and Mair Bank. In addition, the inner ebb-tidal delta comprised of the Mair and Marsden Banks is an important site culturally due to the pipi resource, which has undergone drastic changes over 21

23 the past decade (notably a large decline in the pipi population, a narrowing of the intertidal bank and beach erosion). 46. The sediment transport pathways are complex in the vicinity of the ebb tide shoal and Mair Bank, with some overwash of sand from the delta to the channel, but also another sediment transport pathway due to tidal flows and the relatively erosion resistant surface of Mair Bank, with tidal flows moving sediment in a south easterly direction along the southern face of Mair Bank, then entering the channel to flow into the harbour (Volume 3 part 10). The proposed capital dredging to deepen and realign the entrance channel will result in the a 3,470,000 m 3 from the deeper part of the ebb tide delta, and 150,000 m 3 from the shallower (<10 m deep) part of the delta. That is, the capital works are focussed on the ebb-tidal delta. The main areas that will require maintenance dredging is in the vicinity of the proposed berth pocket (due to sand transported from the ebb delta over Mair Bank and eastward) and the outer leg of the channel. 47. Changes in coastal processes on the ebb-tidal delta due to the capital dredging include wave height increases of between 0.1 m and 0.3 m during extreme storm events due to the impacts of refraction on the offshore mound and the changes to the entrance channel. The cumulative impacts on waves of both the offshore and inshore mound are not presented, although can be assumed to be additive. A great deal of coastal change can occur during storm events and increases of 0.1 to 0.3 m in wave height in the sheltered area of the inner ebb-tidal delta have the potential to cause significant change during such events. In addition, there are predicted changes to currents over Mair Bank and through the swash channel (increases and reductions of 0.1 to 0.3 m/s). 48. These are permanent changes to the gross morphology of the ebb-tidal delta (3.7M m 3 over a 1.44 km 2 area), the wave climate and tidal currents. Considered in isolation over short time-scales these changes are considered by Mr Reinen-Hamill and Dr Beamsley to have no significant impacts (in some cases no impacts at all). Without yet considering the additional impacts of targeting the most active part of the delta with maintenance dredging (i.e. the head of the active sediment transport pathway at the location of the proposed berthing pocket) and potential ecological effects and couplings that are integral to stability of the ebb-tidal delta, I do not agree with these conclusions and 22

24 believe that the statements have been made in the absence of any clear evidence. That is there are very obvious large scale changes shown in the model results that will lead to consequent changes and adjustments to physical processes and the geomorphology of the ebb-tidal delta and the Marsden Point sand-spit which it controls. 49. With respect to the impacts of the proposed dredging and marine disposal on the ebb-tidal delta and the nearshore banks, it is important to also consider the ecological components of the system. The ebb-tidal delta is a biogenic feature, how will dredging of the active inshore sediment pathway (in the area of the proposed berthing pocking which is the spur or terminal lobe of the northerly directed sediment transport pathway), and disposal of sand on the toe of the delta every few years impact on its function? In recent years there has been a massive decline in live pipi (Williams and Hume, 2014), which is the main species that comprise the live and dead shell-lag that forms the banks and delta. Juvenile pipi (Paphis australis) recruit to the shallow intertidal area and migrate to deeper water as the grow. In recent years, following the large reduction in live pipi on the banks, there has been significant recruitment to the intertidal area, although they have not been surviving to adulthood (J. Williams, pers. comm.). 50. In recent years there has also been a diminishing intertidal habitat area on the Marsden bank that could well be a factor in the decline of pipi on the bank and the inner harbour pipi beds are no longer viable due to the port construction in the past it has been suggested that encroachment into the channel by the port reclamation has influenced erosion and accretion around the Marsden Point spit (e.g. Barnett,1993), since it interrupts the eastward-directed sediment transport pathway (Figures 9 and 6). In my view, these components are all interrelated, and the relationships between the physical processes and biological factors of the banks need to be better understood in order to properly consider the potential impacts. 23

25 Figure 9. The Port reclamation and other development on the northern side of Marsden Point have the potential to reduce sediment directed eastward and out along the spit s beaches (See Figure 6 which provides a schematic of the local sediment pathways) 51. Dr Coffey s view of the current ecological condition of Mair Bank where there has been a significant, recent population decrease for pipi and a recent proliferation of green-lipped mussels without a satisfactory explanation of why such changes are occurring, is that it is difficult to justify (from a marine ecology perspective) the identification of Mair Bank as a Significant Ecological Area; Dr Coffey does not agree with the Proposed Plan from a marine ecology perspective (i.e. that the Mair Bank should be considered ecologically significant and so afforded the appropriate protection measures). These comments by Dr Coffey completely disregard the importance of Mair Bank in the function and stability of the Whangarei Harbour entrance, and the biogenic service that the shellfish in this location provide. 52. One of the concerns I have mentioned above is the maintenance dredging of the active sediment transport pathway for the proposed berthing pocket. Disregarding the physical changes that will occur due to the proposed deepening, realignment and nearshore disposal (i.e. an increase of 0.2 m/s in the currents along the swash channel and a decrease of 0.3 m/s over Mair Bank) this site includes a dynamic pipi population that has recently been found to have a sharp increase in pipi density, as detailed in the evidence of Juliane Chetham (Figure 10). 24

26 Figure 10. Reproduced from the evidence of Juliane Chetham. 53. It is my opinion that this active area of sediment transport and pipi population dynamics should be better considered and understood with respect to the form and function of Mair Bank and the ebb-tidal delta, rather than disregarded as an insignificant ecological feature which will be impacted insignificantly by the proposed dredging campaign; the biological and physical coupling is a fundamental feature of the ebb-tidal delta, which is a fundamental control feature for the harbour entrance. The morphodynamics of Mair Bank are largely influenced by the armouring provided by live shellfish, such as dense areas of live pipis that provide biological armouring, and their residual shell fragments. 25

27 Therefore, the factors that make-up this biological feature need to be seriously considered. 54. Dr Lohrer s peer-review of Dr Coffey s assessment of marine ecological effects succinctly identifies the coupling of physical and biological processes and the concerns that I have with the assessment of effects; these factors have not been considered in any detail in the application. I support the conclusions of Dr Lohrer, which points out some of the complexities of the biological systems and how the physical impacts proposed capital and maintenance dredging will impact on the the marine ecology. The simplistic statements of Dr Coffey do not support a comprehensive investigation or understanding of the complexities of the biological and physical couplings that make up the ebb-tidal delta and associated banks. Understanding these processes is critical to the sustainable management of the Whangarei Harbour entrance and surrounding marine environment. Climate Change Impacts 55. When the natural processes are combined with the Proposal, Mr Reinen-Hamill considers that this may result in increased erosion pressure on Mair Bank as well as, ongoing shoreline erosion along the open coast beaches adjacent to the Ebb Tide Delta. Subtle changes in the tidal and wave-driven currents over the eastern part of Mair Bank may result in zones of deposition and erosion on the toe of the Bank. This is a description of the potential cumulative impacts of the proposal, could be considered contrary to the previous conclusions of no significant impacts. 56. Mr Reinen-Hamill makes a strong case for the need to place dredged material at the inshore disposal site (Site 1.2) in order to combat climate change/sea level rise (SLR). I am definitely in agreement with keeping any dredged material within the system. The negative impacts of dumping offshore or extracting (e.g. sand-mining) and therefore removing material from the active system are also well known worldwide. However, whether the location selected is the most appropriate to address climate change impacts is not demonstrated nor the need for this to be addressed in this location presented or other methods explored. The effect of this material placement may also have impacts on the biogenic components of the Mair Bank that have not been considered, as 26

28 discussed above). There is an increased focus on SLR through Mr Reinen- Hamill s evidence (i.e. from how it may impact on the Mair Bank early on in his evidence to how material must be placed to combat SLR (e.g. para 72)). I consider this over-stated and detracts from what the likely changes to the harbour and the surrounding area will likely be from the proposed dredging campaign and ongoing maintenance dredging. The ebb-tidal delta and entrance channel has remaimed stable for at least the past 76 years, a period during which SLR has also occurred. 57. There is no doubt that New Zealand should be considering the likely impacts of climate change and SLR in order to be able to respond to them. However, considering this uncertainty should result in a precautionary approach when considering the potential effects associated with the proposed activity. Mr Reinen-Hamill considers these impacts in Section 4.2 (Volume 3 part 10), with SLR leading to an increased tidal prism or tidal velocities, which may lead to increased erosion of the channel and ebb-tidal delta, or potentially to infilling of the harbour. 58. Mr Reinen-Hamill presents recent research (Van der Wegen, 2013) that has identified that tidal asymmetry is a key driver of change within the estuarine area over long timescales where sea levels are increasing. Tidal asymmetry leads to small spatial gradients in tide residual sediment transport which results in morphodynamic development of the estuary. It is noted that these are also potential effects of the proposed removal of 3.7M m 3 from the harbour entrance (Stive and Rakhorst, 2008), as discussed above, which have the potential to occur over a short/compressed time-scale (i.e. 6 months) due to the proposed dredging campaign, and therefore have a more immediate impact than SLR. 59. It is also notable that during the 76 year period that the Mair Bank and harbour entrance was found to be stable, sea level rose 0.15 m (re: the Auckland tide gauge record and estimated average SLR for the NZ east coast). The impacts of sea level rise on coasts, beaches and estuaries is not well understood. Given the high stability of the system over the past 76 years during which the sea level increase 0.15 m, there is no evidence to suggest that during the course of the 35 year resource consent SLR will have profound impacts on Mair Bank/the 27

29 ebb-tidal delta and it must be addressed by the continual addition of dredged sediment to the offshore toe. 60. I agree that it is preferable to retain sand in the system and prepare for the impacts of SLR, but the works undertaken do not demonstrate that the toe of the Mair Bank is the best place to address these issues. S42a Officer s Report 61. Potential physical effects in the area of the ebb tide delta and on Mair Bank are seen by the report writer as critical considerations to the acceptability (or not) of the proposal (paragraphs ). With respect to the effects, the officer s report states that it is recognised that both the capital dredging and ongoing maintenance dredging may result in a net loss of sediment from the ebb tide delta over time that may not be replenished from natural sources. Spoil deposition at Disposal Site 1.2 from capital and maintenance dredging will replenish sand in the more active shallow area above 5m depth. However, capital dredging in deeper outer channel areas and disposal at Disposal Site 3.2 will see sediment lost from the active ebb tide delta system. This is likely to result in both a reduction in bed level and a reduction in overall size of the delta over the long term. Vertical changes of between 0.16m to 0.23m are predicted over the 35-year consent period sought. Horizontal reduction of the current 5.6 km seaward extent of the delta to 15m contour is expected to be around 70m over the same period. 62. In paragraph 193, the reporting officer outlines the concerns: Ensuring minimised effects on these areas appears reliant on the continued placement of maintenance dredging spoil at Disposal Site 1.2. Several issues arise: (a) Exact timing of maintenance dredging and volumes of sediment to be removed and disposed of won t be known until after capital dredging is completed if lengthy period between campaigns and/or limited volumes to be removed then ETD replenishment could become compromised. 28