DIXON & CO LAWYERS PO Box 10 081

Dominion Road Auckland 1446

Telephone: (09) 620 6240

Facsimile: (09) 620 625

Email: kelly@dixonandcolawyers.com

BEFORE THE NORTHLAND REGIONAL COUNCIL

APP.307197.01.01

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

1

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 4th 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

2

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);

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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 2014. 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);

4

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, 2015. 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;

8.10 A range of published literature pertaining to the impacts of harbour

deepening.

Summary

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

5

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 industry-

standard models have been applied to the investigations1, 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 m3 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.

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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 dredging2.

15. The estimated dredging and disposal volume and areas of disturbance are for

the proposed entrance channel deepening campaign 3,700,000 m3 and 1.44

km2, 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 m3 of sediment) over a large area (1.44 km2)

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 cross-

sectional 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 m3 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).

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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)

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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 m3 is to be

removed from the throat (a cross-sectional area of some 660 m2) (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

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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:

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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.

11

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 m3 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

12

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 m3 (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

13

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 areas3 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.

14

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%.

15

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).

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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.

17

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

5.5.2 – 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 m3

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

18

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 m3 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 m3 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

19

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 174-176),

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 8.

41. 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

20

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

21

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 m3 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

22

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 m3 from the deeper part of the ebb tide delta, and

150,000 m3 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 m3 over a 1.44 km2 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

23

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.

24

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).

25

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.

26

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

27

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 m3 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

28

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 190-192). 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.

29

(b) Need for maintenance dredging expected to diminish over time –

should the ETD and Mair Bank be more sensitive to effects than

predicted then options for remediation appear limited long-term.

Additional sediment may be needed from other sources.

(c) Uncertain how much spoil placed at Disposal Site 1.2 will actually

migrate northward and therefore whether the ‘replacement’ volume

would indeed match that proposed to be removed from the active part

of the ETD.

(d) An ongoing evaluation of the amount of sanded to be returned is

needed – requires operational detail not included in the reports

available. Ongoing evaluation required to ensure no adverse effects on

the bank and its resident pipi population as a result of sand inundation.

63. In addition to the various concerns and unknowns that have not been

evaluated, which I have described in the section in relation to the ebb-tidal delta

and Mair Bank above, it is my opinion that there is little confidence in the actual

impacts that the proposal will result in and that a precautionary approach is

required.

Cumulative Impacts

64. The cumulative impacts of the various modifications to coastal processes and

biological processes have been poorly addressed (to my knowledge, the latter

not addressed at all). In addition, the cumulative impacts of previous port

developments at Marsden Point have not been well addressed, while the

cumulative impacts of the consented land reclamation have been

disregarded/down-played in order to reduce the proposed shift in the tidal

phase from 7 minutes to 2 minutes (paragraph 236 and 237 of Dr Beamsley’s

evidence). Impacts of previous port developments and dredging on sediment

transport, biological communities, tidal currents, etc., have not been

considered.

65. Many estuaries worldwide have been progressively modified from their natural

state to keep up with the expansion of the shipping industry. Channel

deepening and land reclamation along inter-tidal margins can heavily influence

tidal currents, tidal phase, sedimentation rates, erosion and deposition

30

regimes, sediment morphology, salt-wedge intrusion, salinity, circulation,

flushing, etc., etc. However, since most dredging studies are conducted project-

by-project, they have often concluded relatively small changes or short-term

effects, and the long-term cumulative effects of combined dredging and

reclamation often escape attention.

66. As with documented impacts of entrance channel deepening and marine

dredge disposal, there are a number of international studies which address

these long-term cumulative (and in all cases report here, negative) effects on

harbours and estuaries:

66.1 Van Der Wal et al. (2002) investigated the long-term dredging impacts

of the Ribble Estuary, UK, through the period 1904 – 1979.

66.2 Sherwood et al. (1990) report on the influence of dredging and land

reclamation on Columbia River Estuary, USA, through the period 1909

– 1981.

66.3 Cox et al. (2003) report on the salt marsh response to long-term channel

deepening and land reclamation in the Westerschelde Estuary,

Netherlands through the period 1955 – 1996.

66.4 Nichols & Howard-Strobel (1991) considered the estuary response to

long-term dredging and land reclamation in Norfolk Harbour, USA

through the period 1880 – 1982.

66.5 Goodwin (1987) investigated tidal flow, circulation and flushing changes

caused by dredge and fill in Tampa Bay, USA through the period 1880 –

1972.

These studies all demonstrate that it is usually the long-term cumulative effects

of continual channel dredging (capital and maintenance), combined with

incremental land reclamation that drives the overall degradation of these

estuarine systems. A similar approach to this latest phase of port development

needs to be undertaken to consider how the current proposal will influence the

cumulative impacts to Whangarei Harbour and the surrounding marine

environment.

31

Conclusion

67. In summary, many of the conclusions drawn from the changes predicted by the

numerical models in the technical reports are based on relative change (e.g.

percentage difference). However, 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.

68. 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, the tools have not been appropriately applied or interpreted in many

of the investigations presented. 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 m3 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.

69. The Whangarei Harbour entrance is a unique situation with respect to the wider

geomorphology creating a wave gradient onto an ebb-tidal delta comprised of

an armoured sand bank, with the armour comprised of live and dead shell

material. In recent years there have been massive declines in the live shellfish

population, while the proposal is to remove some 3.7M m3 of material from it

and deposit in mounds in different areas, which will result in morphological

change to the delta, as well as wave and current changes, and also the ongoing

maintenance dredging of the most active part of the delta. There are obvious

couplings between physical processes and marine ecology that are not well

understood, and so there is a need to proceed with caution until they can be

understood and quantified in order to sustainably manage the harbour, the

entrance and the surrounding resources. The tools have been developed, but

not applied well, especially in the absence of considering the large volume of

information available on the likely impacts of changes to harbour entrance

channels.

32

70. The biological and physical coupling is a fundamental feature of the ebb-tidal

delta, which is a fundamental control feature for the harbour entrance. Without

fully understanding it and what the impacts of the proposed dredging campaign

will be there are not only risks to the cultural and ecological values off the ebb-

tidal delta and associated banks, but also the potential to have negative

impacts on the integrity of Marsden point; e.g. chronic erosion of the spit due

to the various ‘subtle’ changes in physical and biological processes requiring

100’s of meters and millions of dollars of shore protection measures.

71. It is my opinion that the Patuharakeke Trust Board’s initial concerns was that

there exists uncertainty as to whether this project will result in significant

environmental harm and consequently undermine their ability as Kaitiaki to

take care of and restore these highly-valued coastal sites (their taonga) is valid,

especially with respect to impacts on the ebb-tidal delta and Mair and Marsden

Banks. For that reason, I accept the position adopted in the evidence of Ms

Chetham and Mr Badham that the RNZ proposal should be declined to ensure

sustainability and the application of kaitiakitanga.

Shaw Mead

21 February 2018

33

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