Causeways and Barrages within the Bay of Fundy, Nova

Scotia, Canada:

A study tour to investigate their relevance as analogues for

possible tidal power barrages in the UK

Roger K.A. Morris

7 Vine Street, Stamford, Lincolnshire PE9 1QE

December 2008

This report should be cited as: Morris, R.K.A., 2008. Causeways and barrages within the Bay of Fundy, Nova Scotia, Canada: a study tour

to investigate their relevance as analogues for possible tidal power barrages in the UK. Unpublished

Front cover photo: Moncton Causeway sluice (New Brunswick)

CONTENTS

Chapter

No.

Title Pages

Preface

Acknowledgements

Executive summary

1. Rationale …………………………………………………………………….

2. Contextual setting: the Bay of Fundy ……………………………………….

3. Annapolis Royal …………………………………………………………….

4 Moncton and Windsor Causeways

5 Fish Passes

6 Analysis

7 Conclusions

8 References and bibliography

PREFACE

This report provides an account of a visit made to Nova Scotia, Canada between 17 and 24 October

2008. My travels included visits to all three of the major tidal causeways. In addition, a substantial

number of the 25 or more tidal causeways created to maintain the coastal road system were also

observed. The resulting report does not seek to achieve comprehensive coverage of all of the road

causeways and provides only a limited overview of the impacts of causeway and barrage

construction. Detailed analysis is not possible without access to time-series aerial photographs and

ortho-rectification. Consequently the observations recorded provide an initial analysis that I hope

will provide the foundations for others to follow-up. Some work has already been done in Canada,

but unfortunately rather a small amount lies within the readily-available peer-reviewed domain. I

hope my visit will have stimulated others to assemble existing data and present it in journals for

wider use.

The findings of this study are offered as a contribution to the ongoing debate about the possible

opportunities afforded by tidal power generation using barrages and possibly lagoons. The

interpretations are my own, and do not represent the views of my employers who were in no way

associated with the study: I met all of the costs and the time was provided through six days annual

leave. This written account was compiled during weekends and evenings and is equally

independent of any other party.

Joggins Cliffs, Chignecto Bay – world-famous geological site for fossilised tree stumps containing lizard remains.

ACKNOWLEDGEMENTS

This study tour relied heavily upon assistance from Dr Graham Daborn, formerly Director of the

Acadia Centre for Estuarine Research (ACER) at Acadia University, Wolfville, Nova Scotia.

Without Graham’s help and enthusiasm it would not have been possible to achieve as much detail in

such a short time. Graham also facilitated a round-table meeting with several of his colleagues at

ACER that was a considerable help in formulating thinking about issues and current levels of

understanding about the implications of tidal causeways and barrages.

Steve Hawbolt and Andy Sharpe at Clean Annapolis River Project (CARP) provided a warm

welcome and access to the library of reports held by CARP that are otherwise almost impossible to

obtain. Jeffrey Glenan at CARP kindly helped me by undertaking a substantial volume of

photocopying to make available key reports that I felt worthy of further analysis.

Finally, the people of Nova Scotia offered tremendous warmth and hospitality that made my visit

both enjoyable and productive.

I thank you all.

Roger Morris, December 2008.

EXECUTIVE SUMMARY

1. Between 17 and 24 October 2008, the tidal energy barrage at Annapolis Royal, Nova Scotia,

was visited together with the tidal causeways at Moncton, New Brunswick, and Windsor in

Nova Scotia. All three have headponds with sluices that permit control of water levels.

2. Annapolis Royal started life as a flood control causeway like the other two structures but was

converted to a tidal energy barrage in the early 1980s. All three structures show evidence of

erosion problems within the headpond that are exemplified by an absence of foreshores, steep

banks, rock armouring and evidence of bank erosion. Particular post-construction research

attention has been paid to Annapolis Royal because of repeated claims by landowners around

the headpond that erosion is directly related to the construction of the tidal power plant. These

assertions have not been borne out by several studies and the problems of erosion have been

attributed to three key factors:

Sediment shortfalls arising from sedimentation in deeper water within the headpond;

Weakening of foreshores by ice scour; and

Wind-driven wave erosion.

3. These studies did, however, implicate the tidal energy project as a secondary cause of erosion

because re-opening the headpond to tidal influences meant that the erosion regime was

exacerbated by fluctuating water levels. A consequence of this is restrictions on the permitted

changes in water levels at Annapolis Royal, to reduce the impact of wind-wave propagation and

related foreshore erosion. This means that the barrage does not generate at its full design

performance.

4. Downstream of the three barrages/causeways, different responses have occurred. At Annapolis

Royal, foreshores have eroded, especially in front of the Fort Anne historic monument on the

eastern downstream bank. At Windsor and Moncton, foreshores have advanced and extensive

mudflats and saltmarshes have evolved. These latter responses compare with similar responses

caused by estuary foreshortening in the UK such as the Dee estuary in north-west England.

5. The reasons for differing responses downstream of the barrage/causeway principally lie in

sediment availability. Within the Annapolis basin, the majority of sediment has fluvial origins

(which on visual inspection there appears to be comparatively little). At both Moncton and

Windsor, marine derived sediments dominate the system. These marine sediments are largely

the result of soft cliff erosion which leads to very high suspended sediment levels in Minas

Basin and Chignecto Bay, giving the water a muddy appearance and leading to the Pettitcodiac

River being referred to as The “Chocolate River” (Wikipedia website).

6. My suspicions are that erosion at Fort Anne is not wholly related to interruption of fluvial

sediment sources. The sediment plume illustrated in aerial photographs I have seen are

remarkably localised. Moreover, as the overall morphology of the estuary was fundamentally

changed by the initial causeway and latterly by the tidal power plant the explanation is likely to

be linked to changes to the thalweg.

7. The processes that have determined the responses of the three affected estuaries can be clearly

identified. As such, all three causeways and headponds offer useful analogues that reinforce the

analysis provided by Prof. John Pethick’s thesis (2007) on the way that the Severn Estuary

might respond to a tidal barrage. All three examples also point clearly to the validity of the

reservoir analogue that I have proposed (Morris, in press).

8. Both the Moncton and Windsor causeways point to a possible alternative response by a barrage

proposal at “the shoots”. Here, it is possible that sandy sediment within the main body of the

Severn Estuary might be pushed upstream and deposited in front of the barrage to create a new

body of saltmarshes. The probability of this type of response is likely to increase further

upstream as the impact of barrage construction on tidal propagation diminishes and allows

continued sediment mobilisation from sub-tidal sinks during spring tides

9. This visit has determined the presence of a large body of unpublished information, some of

which is of considerable interest to many aspects of the debate about barrages. Issues pertaining

to fish are of very relevant. Declines in the age classes of shads using the Annapolis River are

particularly worrying. Meanwhile, data on zooplankton offer an alternative insight into

suggestions that turbid waters are not biologically productive and would support more biomass

if sediment levels are depressed.

1. RATIONALE

1.1. Tidal energy barrages are currently under consideration for a number of English estuaries,

most notably on the Severn Estuary but conceptual ideas have also been raised for several

other estuaries including the Mersey Estuary, Morecambe Bay, the Solway Estuary and The

Wash. Such proposals, were they to be developed, might be expected to lead to significant

changes to the physical regime of the estuary or bay concerned.

1.2. Most work has been done for the Severn Estuary and there is a substantial body of literature

that seeks to provide an understanding the possible implications. The geomorphological

response to a Severn tidal barrage is a matter of particular interest because it is one of the

most frequently debated options and is potentially controversial with strong proponents and

equally robust detractors. But, geomorphological changes are equally relevant to other

barrage and causeway proposals because they have far-reaching implications for a diverse

range of interests including flood risk management, safeguarding infrastructure and

conserving and enhancing wildlife. The nature of the possible response is a matter of debate

and at the moment there are two differing models under consideration:

Accretionary model: the established model used as the basis for many predictions made

in the period since the original tidal barrage studies ceased at the end of the 1980s. It

proposes that a reduction in tidal energy will lead to increased sedimentation on

foreshores and an improvement in the stability of sediment. This model forms the

foundation of claims that remaining mudflats will be able to maintain the waterbirds for

which the Severn Estuary is noteworthy (Kirby & Shaw, 2005). Analogues used to

underpin this model include La Rance, the largest tidal energy barrage currently

operating, and foreshore progradation at Cardiff docks.

Erosionary model: argues that the creation of a barrage will alter the energy regime in

such a manner that foreshore erosion will feed subtidal accretion for a long period until

the estuary has accumulated sufficient sediment to allow mudflats to re-establish

(Pethick et al. in press; Morris, in press). This model draws upon the storm surge

barrage across the Eastern Schelde as its underpinning analogue, but also includes

reservoir foreshore evolution as a further body of evidence.

1.3. Both models draw upon data for established structures. The objectives of the structures

involved are completely different, however: one is a tidal energy barrage whilst the other is

designed to reduce the impacts of storm surges. An obvious and occasionally voiced view is

that the Eastern Schelde model is not valid because it is not a tidal energy barrage. In

addition, views have been expressed that in the case of the Severn there would still be a

substantial tidal range after construction of a barrage and the estuary might therefore be

expected not to respond as negatively to reduced tidal energy as some have postulated.

1.4. The Bay of Fundy offers further possible analogues. When I decided to visit the Bay of

Fundy, literature and website reports appeared to support the proposed erosion models

(Pethick, 2007; Morris in press). Unfortunately, the level of information available in the peer-

reviewed published literature is comparatively limited and there appeared to be a range of

evidence that was in need of further investigation. I therefore felt that there was a need to

visit the Bay of Fundy to collect information that could be evaluated as part of the

geomorphological studies underpinning the consultants’ studies for the Department of Energy

and Climate Change (DECC).

1.5. This study therefore sought to investigate the main analogue Annapolis Royal, which is a tidal

energy barrage whose output is an order of magnitude smaller than La Rance. In addition,

two other major structures appeared to fit the models proposed. These were the causeways at

Moncton and Windsor in New Brunswick and Nova Scotia respectively that created

headponds similar to those created by tidal energy barrages. Whilst investigating these

structures and the responses both upstream and downstream, travel around the Bay of Fundy

also permitted extensive access to culverted road causeways across many of the tributaries to

the Bay. Observations on these are included to provide as comprehensive a review as

possible.

2. CONTEXTUAL SETTING

GEOGRAPHY OF THE BAY OF FUNDY

Figure 1 The overall geography of the Bay of Fundy. Source Fundy Issues #1 (revised. Spring 1999).

2.1. The Bay of Fundy comprises a bifurcated inlet that runs almost from west to east between

Nova Scotia and New Brunswick, emptying into the Gulf of Maine (Figure 1). Its geology is

complex with harder less erodible rocks in the outer, western, parts of the bay, and softer

sandstones, mudstones and glacial material to the east. As a consequence, the waters of the

outer bay are relatively sediment free and foreshores are populated with a well-defined fucoid

zone. Further upstream within Minas Basin and Chignecto Bay the waters are heavily

sediment laden, assuming the same reddish colour of the Triassic sandstones that continue to

contribute sediment to the system.

2.2. The Bay of Fundy is particularly noteworthy for its high tides that can exceed 16 metres on

occasions (Figure 2), giving it the highest tidal range in the world. This tidal range makes the

Bay extremely dynamic with considerable scope for sediment movement and equally high

potential for tidal energy generation. Various conceptual proposals have been advanced but

attempts to harness the tidal power have so far been confined to a small tidal range power

station at Annapolis Royal at the mouth of the Annapolis River.

2.3. Many rivers enter the Bay of Fundy and the Atlantic coast of Nova Scotia and consequently

there are many estuaries that exhibit a wide range of morphological evolution. On the

Atlantic coast estuaries such as the La Have, Medway Harbour and Lunenberg Harbour

(Photograph 1) are predominantly free of sediment and have a form that most closely

approximates to the classic ria with clear waters and limited extents of inter-tidal mudflats and

saltmarshes. Their tidal range is in the order of 2-3 metres. From my casual observations,

these estuaries appear to derive their sediments from fluvial sources whilst the wave energy

regime means that most beaches are highly sorted with limited fine sediment and widespread

distribution of heavier clasts. On the coast between the Have and Medway Harbour, I

encountered a barrier beach with large shingle cobbles in front of a lagoon (Photographs 2 &

3).

Figure 2. Tidal range within the Bay of Fundy and east coast of Nova Scotia Source: O’Reilly et al. (2005)

Photograph 1. Lunenberg Back Harbour at high tide with a small fringe of Spartina

alterniflora in the foreground.

Photograph 2. Barrier beach – Atlantic coast, Nova Scotia between Le Have Estuary and

Medway Harbour.

Photograph 3. Lagoon behind barrier beach – Atlantic coast, Nova Scotia between Le

Have Estuary and Medway Harbour.

2.4. In sheltered situations within the Bay of Fundy, where fluvial or marine derived sediments are

available, saltmarshes can be extensive (Figure 3 and Photographs 4 & 5). Many fill the tidal

basin and suggest that morphological evolution has assumed something close to “most

probable state”. In the bigger estuaries this land has largely been separated from tidal

conditions by sea walls that have allowed saltmarsh conversion to various agricultural uses.

Figure 2. Major saltmarshes in the Bay of Fundy: 1. Annapolis; 2. St John; 3. Shubencadie; 4.

Avon; 5. St Croix; 6. Pettitcodiac; 7. Trautrama; 8. Missaquash. (Note, the saltmarshes in the

Annapolis basin are now largely supra-tidal). Source Dykes, Dams and Dynamos: the impacts of coastal structures. Fundy Issues 9: Autumn 1996.

2.5. In most instances saltmarshes within estuaries have been divided by a causeway that carries

the main roads (within the Bay itself this predominates). These causeways include a conduit

for the river and consequently the system is still free to accommodate most tides. However,

the highest tides must be constricted and consequently the majority of saltmarshes must have

experienced some limited reduction in the upper end of the tidal inundation.

Photograph 4. Saltmarsh in Copequid Bay.

Photograph 5. Saltmarsh with wooded outcrop, Copequid Bay.

2.6. Unlike eastern English UK saltmarshes, those of the estuaries I visited have a much less

complicated morphology and vegetation zonation that reflects the nature of the sediments, the

tidal range and associated phyto-sociology. Most sediments appear to be largely non-cohesive

(mainly sands and silts) and consequently channel morphology tends towards a system that

undergoes periodic slumping and development of mobile sandbars. The upper levels of the

channel banks are largely populated with Spartina alterniflora1, which is a coarse tall species

that can grow to maybe a metre or more in height and is largely sheared by ice in the winter.

Ice-sheared Spartina stems form dense thatches along the upper inter-tidal and this biomass is

a major contributor to estuarine productivity each year (Graham Daborn pers. com.).

2.7. Higher land within the saltmarsh is populated by Spartina patens which is much shorter and

forms a dense sward that at the end of the summer assumes the appearance of “hay”, giving

rise to its colloquial name “marsh hay”. A further coarse grass was noted in places – this grew

to a height of perhaps 1.5 metres but I’m afraid I could not identify this to genus. Forbs are

relatively scarce within much of the saltmarsh, with the exception of seaside goldenrod

Solidago sempervirens that was often abundant but not dominant (Photograph 6). Other

plants noted included a species of Triglochin (? maritimae) and also a straggly Atriplex. In

one location I noted a species of Suada on muddy corner of the strand line. In places,

freshwater influences were also recognisable with beds of bulrush Typha latifolia.

1 Spartina alterniflora is the species that originally hybridised with Spartina maritima in the UK to create firstly S. x

townsendii and subsequently Spartina anglica.

Photograph 6. Saltmarsh at Fort Anne showing zonation between Spartina alterniflora and

Spartina patens.

3. ANNAPOLIS ROYAL

Souce: http://www.aquatic.uoguelph.ca/rivers/anmap.htm

History – the headpond

3.1. The Annapolis Royal tidal power station lies within a causeway that was initially constructed

in 1960 and which led to the most profound changes to the morphology of the Annapolis

Estuary. Consequently, impacts arising from the power station and the initial causeway need

to be separated before any conclusions can be drawn about the impact of a tidal range power

station. The sequence of construction comprised two phases:

Creation of the initial causeway commenced with construction of sluice gates on the

southern side of the former constriction to the Annapolis Estuary (Figure 3).

Subsequently, a rock-cored causeway closed the original estuary mouth. The consequence

of this first stage was the creation of a “headpond” with limited saline interchange but

scope for sluicing. This removal of tidal influences led to a reduction of water heights in

the “headpond” and consequently led to a reduction in the tidal range from 6.3 metres to

about 0.3m (MARTEC, 1987). Around 1600 acres of former saltmarsh was permanently

exposed or taken out of a flooding regime and available for agricultural use.

Construction in 1984 of a turbine hall and fish pass in the middle of the island that

formerly comprised part of the original shoreline. This second stage led to re-

establishment of a tidal regime but the limited cross sectional areas of the original sluice

and the turbine sluice are substantially smaller than the original cross sectional area of the

mouth. Consequently water levels rose from around 0.9m above geodetic datum to 1.86m

above datum (MARTEC, 1987).

Photograph 7. Annapolis Royal turbine house and visitor centre

3.2. From an early stage, erosion within the headpond was identified as a problem. Work for the

tidal power project Environmental Impact Assessment (MARTEC, 1980) identified erosion as

an ongoing process, especially in the lower basin, with an estimated loss of 35 ha between

1954 and 1980. Importantly, neither the MARTEC (1980) report, nor a subsequent

investigation (CAPG, 1982) predicted accelerated erosion rates arising from tidal power

production.

3.3. Concern about erosion became more pronounced however after the commencement of tidal

power generation. MARTEC (1987) reported that qualitative observations during field

surveys suggested that some areas that were previously stable had commenced erosion

following the operation of the tidal power station, whilst other areas of erosion had become

more severe.

3.4. The 1987 MARTEC report also suggested that although the headpond had undergone a period

of erosion following causeway construction by the late 1970s this more pronounced rate of

erosion had declined and an “equilibrium condition” had been reached. Erosion after this

period was considered to be more natural and the study sought to establish the background

levels of erosion to form the basis for determining how much additional erosion was caused

by the tidal power station. Their work involved:

Use of aerial photographs to establish changes in the upstream shoreline from 1977

onwards. The period from 1977 to 1982 was taken as the “natural” rate of erosion that

would be used to form a baseline over which changes in erosion following the initiation of

power production in 1984.

Determination of bank profile and nearshore bathymetric changes along shoreline sections

surveyed by the CAPG study (1982) and survey of newly eroded shorelines that were

considered as stable in 1982.

3.5. The outputs of the 1987 MARTEC report are however presented with considerable caution. It

includes a strong qualifying statement to the effect that there was uncertainty about the

confidence limits that could be placed on predictive work and that any analysis should be

regarded as strictly a first order level of change. In other words, the report could identify the

likely direction of travel but various factors might have a significant effect on the precise

outcomes. The report provided a series of conclusions that are very relevant to barrage

operation elsewhere. It identified the following erosion pathways:

i. The addition of a further 3 feet of water within the headpond as a result of

resumed tidal influences had reduced the scope for attenuation of wave, current

and ice-induced erosion.

ii. “Increased lateral and vertical movement of ice, particularly during spring

breakup”.

iii. The role of vertical bank stratification in determining susceptibility to wave,

current and ice erosion.

3.6. The final conclusions of the MARTEC report were to emphasise that the establishment of

tidal power generation had not precipitated erosion but had served to exacerbate an existing

problem. Their recommendations included changes to the operating rules for the tidal power

station to reflect the “vulnerability of the headpond shoreline to physical forces causing

erosion. In particular, they were trying to secure an operating regime that allowed the

development of a more stable foreshore profile that would achieve a more stable state that

attenuated erosive forces. In other words, they were recommending the need to maintain

water levels such that a wave platform could develop in an appropriate location and that this

could be maintained.

3.7. Studies into foreshore erosion within the Annapolis headpond have continued since 1987 and

a further commissioned report (Oswalt & Patrick, 1999) provides useful additional indications

of the direction of travel with regard to ongoing foreshore erosion.

3.8. Oswald & Patrick (1999) make the important distinction between a causeway headpond and a

tidal barrage, which they describe as a “river-reservoir system”. Furthermore, they identify

erosion problems as induced by “human activities”. Their report does, however, indicate that

the rate of erosion had declined between 1991 and 1998 and emphasises the importance of

increasing “fetch” that “resulted in increased wind generated waves operating on banks

already susceptible to erosion by sloughing”. This process has led to bank over-steepening

followed by bank failure through internal shear.

3.9. In the period since 1998, concern about erosion has not fully abated and this has been further

investigated by a graduate student as part of their Masters thesis (MacFarlane Pierce, 2007).

The map produced as part of this study was made available to me by the Clean Annapolis

River Project (CARP). It shows that for the most part, erosion is ongoing but there do appear

to be areas of accretion which would be wholly consistent with morphological evolution

arising from deposition of sediment in the headpond and gradual evolution of a new

equilibrium form. Photographs held by CARP also show evidence of developing Spartina

alterniflora marsh in front of some eroded banks: seemingly the wave platform must have

evolved sufficiently to attenuate wave energy and accommodate some limited foreshore

evolution.

History – outer tidal basin

3.10. It would appear that the influence of the tidal causeway and tidal power station did not evoke

immediate concern about evolving foreshore morphology. However, in the mid-1990s

evidence of foreshore erosion was recognised with the exposure of timbers that originated

from constructions over 300 years ago. Subsequently, the skeleton of a victim of starvation

and disease within the fort during a period of siege during Anglo-French hostilities was

uncovered. The fort is now protected by a very substantial rock armour berm that is illustrated

in the American Army Corps of Engineers’ Coastal Engineering Manual (USACE, 2002).

3.11. The erosion at Fort has been studied and there are several detailed analyses that I have as yet

to gain access. Daborn in Greenberg et al., (1997) describes the history of investigations into

the erosion at Fort Anne which seems to have coincided with the construction of the original

causeway in 1961. It is concluded that the cause for this saltmarsh erosion arises from

depletion and interruption of sediment supplies arising from the construction of the Annapolis

causeway, but this conclusion is reported to remain uncertain. Aerial photographs which

graphically depict a sediment plume for approximately 100 metres off the Fort Anne

foreshore that extends round into the Allain River suggest a second pathway.

3.12. The causeway at Annapolis involved cutting a new channel on the eastern side of the estuary

to feed the original sluice system before the original estuary mouth was closed. Thus, the

limited remaining exchange between the headpond and the remaining estuary was shifted

from the western side of the estuary to an easterly location and consequently the thalweg

arising from the outfall would differ substantially from the original thalweg. When the tidal

turbine was installed in the 1980s, this was within the remaining central island that formed the

causeway and consequently a new location for the thalweg was established. This involved

considerably more tidal exchange and consequently tidal energy on both incoming and

receding tides would have been stronger because of the existence of the headpond. This too

would have been in a different location to the original thalweg and the sediment plume arising

from the Fort Anne foreshore seems to suggest that it now strikes the Fort Anne foreshore.

3.13. From this analysis, I suggest that the mechanisms responsible for the changes at Fort Anne are

more complex than simple sediment starvation and consequently this erosion pattern cannot

be used as an analogue for projected erosion patterns in the outer Severn Estuary arising from

a Cardiff-Weston tidal barrage.

Personal observations

3.14. My visits were largely confined to the causeway, tidal power station and sluice. Fortuitously,

I managed to observe both the top and bottom of the tides and aspects of the causeway in

operation. Unfortunately, the turbine was out of commission and undergoing maintenance

(which had been ongoing for the summer). Graham Dabron kindly showed me various

localities upstream of the barrage and also locations at Fort Anne and at Port Royal – these

latter on a falling tide and towards the bottom of the tide.

3.15. Much of the tidal headpond appears to be heavily rock armoured and consequently evidence

of erosion is not readily apparent from the causeway. The presence of rock armour is,

however, indicative of an issue. One key exception to this evidence was a large failure in the

rock armour on the northern side of the original sluice cutting (on the seaward side) – see

photograph 8.

Photograph 8. Rock armour failure within the outer basin of the Annapolis sluice channel.

3.16. Upstream of the main headpond, relatively narrow reaches of the tidal river exhibit

characteristic features of erosion with deep undercuts preceding bank failure (photograph 9),

steep or vertical banks and areas of rock armouring (photograph 10).

Photograph 9. Close-up of foreshore erosion between the rock armour in photograph 10

and the tree, top right. This illustrates rotation of the bank and undercutting that leads to

failure of the bank.

Photograph 10. Foreshore armouring within the upper end of the Annapolis headpond at

Granville Centre

3.17. Within the tidal basin outside the causeway the foreshores appear to be heavily influenced by

erosion with the most pronounced impacts at Fort Anne where the foreshore appears to have

dropped by between 2 and 3 metres. Lateral transgression of the remaining saltmarsh is

prevented by rock armour that is by any standards imposing (photographs 11 & 12).

Elsewhere, the foreshore comprises a mixture of rocky material and heavier clasts with

limited fine sediment or sands. This is typical of many of the foreshores within estuaries with

high energy regimes that prevent sediment deposition.

Photograph 11. Rock-armour protection of foreshore and saltmarsh at Fort Anne, Annapolis Royal.

Photograph 12. Rock armour and foreshore lowering in front of Fort Anne, Annapolis Royal.

3.18. Access to foreshores around the Annapolis Estuary is not easy and there are seemingly

relatively few opportunities to observe changes to foreshore profiles. One exception was at

Port Royal where it was possible to observe a large saltmarsh that exhibits quite strong

indications of foreshore retreat (Photograph 13). At this locality there is strong saltmarsh

cliffing with development of a rocky and stony foreshore in front. Such foreshores seem

commonplace when overlying sediments are lost or never existed.

Photograph 13. Saltmarsh cliffing at Port Royal on the northern shore of the downstream Annapolis

Estuary.

4. Moncton and Windsor Causeways

4.1. Moncton and Windsor causeways were designed to reduce flood risk and were strongly

influenced by the Dutch “Delta Project”. These causeways incorporated sluices to allow

flushing of freshwater from the headpond, but largely prevented tidal exchange. Both

headponds retain high levels of water that broadly resemble freshwater reservoirs and they

exhibit similar characteristics.

4.2. A key feature of each causeway was that it substantially reduced the length of comparatively

small estuaries that entered Chignecto Bay and the Minas Basin respectively. Chignecto Bay

and the Minas Basin are both characterised by heavily sediment laden waters and considerable

tidal energy. For example, it is reported that the rumble of boulders being moved within the

Minas channel is audible from boats crossing the channel (G. Daborn pers. comm.).

4.3. Each causeway was constructed some distance upstream causing significant fore-shortening.

This created the environment in which tidal energy was sufficient to mobilise sediment and

carry it upstream where it could be deposited sub-tidally.

Moncton Causeway

4.4. The causeway across the Pettitcodiac River (Figure 4, Photographs 13-16) was completed in

1968 (Niles, 2001). It spans 1040 metres between Moncton and Riverview and created a

freshwater reservoir some 21 km long (Morand & Heralampides, 2006). It incorporates a

road and a sluice with no provision for tidal exchange with the headpond. Consequently,

water levels upstream are maintained at a largely constant level.

Figure 4. Geography of the Pettitcodiac River. Source: Hicklin, 2004.

4.5. From an early stage, concerns arose from the construction of the causeway which were

recently summarised by Niles (2001) as:

Erosion along the banks of the reservoir.

Inability to maintain stable reservoir levels during the summer.

Siltation of the reservoir upstream of the causeway as well as downstream of the causeway

construction.

Unsatisfactory fishway operation.

Ice jamming at the causeway end of the reservoir.

4.6. Fish issues are the primary driver for investigations into how to resolve its impact and there

are now proposals for measures to reverse some of the impacts of the causeway. The

Department of the Environment and Local Government for the Province of New Brunswick

and Fisheries and Oceans Canada (2002) has issued guidelines to inform the process of

Environmental Impact Assessment.

4.7. From a geomorphological perspective, the principle impact of the causeway was to initiate

sediment deposition downstream which is graphically illustrated by two aerial photographs

(Figures 5 & 6). This is readily visible from any point along the Pettitcodiac River

downstream of the causeway. This process is reported to have resulted not only in extensive

saltmarsh evolution, but also to significant diminution of the tidal bore (Morand &

Heralampides, 2006) and a reduction in the overall cross-section of the estuary by as much as

90% (Curran, et al. 2005).

Figure 5. The Pettitcodiac River prior to construction of the Moncton Causeway. In this aerial photograph it

is clear that there is comparatively little upper inter-tidal at the top of the tide. A further feature of note is the

compartively uniform water colour – heavily sediment-laden.

Figure 6. The Pettitcodiac River after construction of the Moncton Causeway. Sediment deposition is

extensive and the channel is restricted to narrow dimensions arising at the sluice gates at the southern end of

the causeway. Evidence of subsequent land-claim is also present on the north shore, some of which

comprises refuse disposal that presents a major problem in relation to measures to restore some level of tidal

interchange. The comparative levels of sediment loading are clear with very low levels upstream of the

causeway and high levels downstream.

Photograph 14. Moncton Causeway looking downstream at the resulting saltmarsh. This

marsh now occupies the majority of the channel with the remaining channel little more than

the width of the sluice.

Photograph 15. Moncton headpond from the Riverside shore. The banks are steep and

largely restrained by rock armour.

Photograph 16. Moncton Causeway sluice. The fringe of vegetation in the foreground is

sea goldenrod.

Windsor Causeway

4.8. This is a much smaller causeway than the Moncton Causeway with a length of 700 metres

(Percy, 2008). It was constructed in 1970 (Proosdij et al., 2004) and closed the Avon River

close to its union with the La Croix River (Figure 7, Photographs 17-19).

Figure 7. Locations within the eastern arm of the Bay of Fundy – Minas Basin. Source: Fundy Issues #19: Fundy’s Minas Basin

4.9. Prior to construction of the causeway, the Avon River supported extensive tidal mudflats and

saltmarshes. Subsequently, these have largely disappeared as described by Percey (2008):

“The causeway largely halted the daily and seasonal large-scale movements of suspended

sediments up and down the river. Upriver, mudflats and shoals were starved of fresh

sediments and steadily diminished in size. Along the riverbanks, salt marshes were also

deprived of both sediments and seawater and thus gradually shrank, some disappearing and

others transforming into freshwater marshes. It is estimated that about 87 hectares (216

acres) of upstream salt marsh were lost in this manner.”

Photograph 17 The Moncton causeway under construction in 1969. This photograph

shows how the developing headpond contained extensive saltmarshes and mudflats that are

no longer evident in recent photographs (see photographs 18 & 19). Source: The “Cause”

in the Causeway: crossing the Avon River at Windsor. Fundy Issues 28. Photograph from

Nova Scotia Dept. of Agriculture archives.

4.10. In common with the Moncton Causeway, the Windsor Causeway has led to foreshore

progradation within the remaining tidal section of the River Avon. This is considerably less

pronounced than the scale of changes within the Pettitcodiac River but extends as far as the

main course of the La Croix River.

Photograph 18. Windsor headpond (Lake Pesaquid) showing near-vertical banks and rock

armour.

Photograph 19. Windsor Causeway, northern end illustrating rock-armouring.

Photograph 20. Saltmarshes in front of the Windsor Causeway. These marshes evolved after a

lengthy period of sediment deposition. In the background is mudflat with occasional tussocks of

Spartina alterniflora that have developed following ice action depositing sediment and rootstock as

islands of higher ground.

Other road causeways

4.11. As one follows the coast of Minas Basin, Copequid Bay and Chignecto Bay numerous

examples of small estuaries with extensive saltmarshes. Almost without exception these seem

to have been divided by a road causeway with tidal access to upstream marshes restricted by

the extent of culverting or bridging. The morphological impacts of these modifications are at

present not entirely clear although I did detect places where a response seemed to be

developing.

4.12. A key point about these causeways is that they cross established saltmarshes. These marshes

show that much of the coastline within the inner bay, where sediment loads are high, have

already evolved to “most probable state” and are as close to a classic mature estuary as might

be anticipated. The effects of reducing tidal access by restricting the latter stages of tidal

inundation on mature saltmarshes have probably been comparatively small in the time since

the causeways were constructed; however the problems can be expected to become more

pronounced in due course as sea level rise progresses.

4.13. In general, the tidal channels exhibit all of the charactersitic features of a hyper-tidal system

with steep banks and partial slumping as a result of low levels of cohesive material within the

sediment. Bigger rivers exhibit sand banks and sand ripples, whilst smaller ones seem to be

comparatively stable. At the moment, it must therefore be assumed that tidal access has not

been so restricted as to prevent the marshes keeping pace with sea level rise. This seems quite

realistic as suspended sediment loads are considerable. However, as sea levels continue to

rise the cross-section of the culvert will act as a brake on tidal ingress and hence on tidal

propagation and sediment deposition on the saltmarshes. A shift towards an erosionary regime

within the inner basin might be expected.

4.14. Some possible indications of changes do seem to be apparent in places, however. Several of

the inner basin saltmarshes seemed to have developed or being in the process of developing

water-filled pans which might be the first signs of saltmarsh degradation. In other places,

Typha beds close to the causeway suggest that marine influences have diminished and that

freshwater influences have started to dominate. Typha beds are also, however, a characteristic

feature of some marshes on the outer side of some causeways, especially close to rising land

where freshwater seepages may be present.

Photograph 21. Riverside Causeway – a tributary into the Pettitcodiac Estuary. The

channel exhibits classic features of largely sandy sediments with concave dimensions where

slumps have occurred. Some of the erosion here might be associated with wave reflection

from the rock armour on the causeway. Beyond the bend in the channel the banks appear to

be better vegetated.

Photograph 22. Saltmarsh on the upstream side of the Riverside Causeway. Here

freshwater pools appear to be developing close to the causeway, possibly indicating

saltmarsh decay.

Photograph 23. Saltmarsh upstream of the causeway at Advocate Harbour on the Minas

Channel. Here, there seems to be extensive pool development that may be indicative of

saltmarsh decay.

Photograph 24. Advocate Harbour on the seaward side of the causeway. This illustrates

the considerable tidal range within the Minas Channel, but also highlights possible

emerging issues as the absence of saltmarsh suggests a much higher energy regime. The

Harbour itself lies is a spit-enclosed estuary with the mouth off top right of the photograph.

5. FISH PASSES

5.1. Issues concerning the impact of barrages and causeways on anadromous fish figure highly

amongst concerns about these structures and have been an important factor in deliberations

about reversing or partially reversing the impediments created by the Moncton Causeway.

Both Moncton and Windsor Causeways have limited provisions for fish passage and

consequently they no longer contribute to breeding populations. At Annapolis Royal there are

better provisions but migratory fish remain and important and unresolved issue.

Species Latin name Notes

American Eel Aguilla rostrata

Atlantic Salmon Salmo salar

Alewife or Gaspereau Alosa pseudoharengus

American Shad Alosa sapidissirna

Blueback Herring Alosa aestivalis Atlantic sturgeon Acipenser oxyrhynchus Several examples of mature sturgeon with

turbine injuries are reported at Annapolis

Royal.

Rainbow Smelt Osmerus mordax

Striped Bass Morone saxatilis

Table 1. Migratory fish within the Bay of Fundy

5.2. When the Annapolis tidal power unit was installed, consent was conditional upon the

incorporation of a fish pass. This structure lies within the same basin as the turbines and

consequently fish enter a strong ebb current with two options – passing through the turbine or

using the fish pass. Precisely how fish avoid the turbines in the face of extremely strong

currents generated is unclear. Indeed, it seems likely to me that the majority of fish using the

fish pass do so as a matter of serendipity!

Photograph 25. Annapolis Royal fish past operating at low tide.

5.3. Reports of heavy fish kill and the behaviour of predators in the vicinity of the turbine stream

provide an insight into the impact of the turbine on fish populations. Seals are known to

frequent the area and it is reported that gulls assemble shortly before the turbine starts to

operate. Similar traits have been reported elsewhere, for example at the Tawe barrage where

fish passage is impeded making them vulnerable to predation whilst congregated waiting to

pass upstream (Jones, 1998). Divers sent in search of tagged fish have also reported the

seabed carpeted with dead fish. These anecdotal accounts provide some indication that the

turbines are affecting fish populations but the degree to which this is detrimental is more

difficult to ascertain. For example, big nuclear power stations occasionally experience high

sprat falls that lead to episodes of major fish kill.

5.4. Impacts on fish seem to fall into three distinct categories:

Fish strike and impact damage;

Cavitation impacts causing soft tissue damage;

Ruptured swim bladders

5.5. There may be differences between fry/larval stages and adults, with larger fish much more

vulnerable to strike impacts from turbine blades. What is less clear is the degree to which

physical impact during passage down the fish pass contributes to overall levels of fish-kill.

6. ANALYSIS

6.1. This study comprised a series of very short vignettes of ongoing morphological evolution at

sites within the Bay of Fundy whose development as causeways was heavily influenced by

the Dutch “Delta” project.

6.2. Several papers describe modelling exercises and there are others that describe many of the

responses. Detailed pre and post-construction monitoring are not readily available, however.

Even so, various studies using time-series aerial photography have demonstrated the nature of

many of the changes.

6.3. These examples help to confirm that tidal barrages in the Bay of Fundy do offer useful

analogues for investigating some aspects of the possible implications of tidal power barrages.

The most useful information comes from the response of shorelines within the headponds of

all three major causeways. Any interpretation of the impact of the Annapolis Royal tidal

power project on the morphology of the Annapolis Basin must bear in mind the two-stage

process that led to its construction. This makes interpretation much more complex.

6.4. There can be little doubt that the primary response of estuarine inter-tidal to reduced tidal

range and creation of a headpond is erosion. All three of the headponds examined display

similar characteristics.

6.5. The best studied is Annapolis Royal because the construction of the tidal power station has

been implicated in the erosion response. These studies show that it is not tidal power

production that is directly implicated. The main cause of problems lies in impoundment and

wind-driven waves as described by several independent studies. Recorded levels of erosion

are relatively small if considered in the context of a barrage across a major English estuary.

But, it must be remembered that the headponds involved are also comparatively small. A

comparison between erosion rates experienced at Moncton and Annapolis in particular,

together with those on the eastern Schelde, might realistically help to inform predictions of

possible responses within English estuaries.

6.6. Whilst detailed studies have failed to establish a direct link between operation of the tidal

power station and bank erosion, reintroduction of tidal influences does appear to be

implicated in increased rates of erosion within the Annapolis headpond. It is significant that

operation of the tidal turbine has been restricted in an attempt to minimise levels of bank

erosion. This evidence serves to confirm that the issue of erosion is one that can be expected

to occur in a headpond irrespective of its purpose. It also corresponds to predictions made that

argue that tidal influences will exacerbate erosion patterns upstream of tidal turbines.

6.7. There are indications that parts of the Annapolis headpond may be developing a shallower

foreshore profile that will support new saltmarsh. This is illustrated by localised examples of

saltmarsh development. I was not able to investigate these in detail, but it seems likely that

sediment accumulation is likely to be most pronounced in those stretches less affected by

wind-wave propagation, in keeping with observations on the Eastern Schelde.

6.8. The Annapolis headpond can be expected to fill with sediment over time because it was

formerly an estuary that was highly dependent upon fluvial rather than marine derived

sediments. Sediment budgets do not appear top be available and consequently the likely time-

scale for in-filling is unknown. The waters downstream of the tidal power station are

seemingly strongly sediment deficient and some analysts have placed the blame for erosion at

Fort Anne on the interception of fluvial sediment by the Annapolis tidal causeway.

Consequently it seems unlikely that the operation of the tidal power station will significantly

contribute to sediment import from offshore sources.

6.9. One of the key issues that I was unable to resolve was how the sub-tidal bathymetry of the

three headponds had evolved. It is unclear how rapidly each one is filling with sediment and

consequently these site are unlikely to be of any real help in exploring rates of evolution

towards a new equilibrium state.

6.10. The response of the shoreline downstream from Annapolis Royal is problematic, but it seems

to me that erosion at Fort Anne is not a strong analogue for the effects of reduced tidal

propagation on the seaward side of a tidal barrage. Erosion of saltmarshes elsewhere

downstream seems to be a more likely analogue but these changes do not appear to have been

well studied. My limited observations suggest that there was saltmarsh cliffing and that there

was ongoing foreshore regression.

6.11. Visual inspection of the fish pass at Annapolis Royal gives cause for some concern. Its

location and the ferocity of the drop make it difficult to believe that it fulfils its full potential

and indeed it might even contribute to fatal damage to juvenile fish. Furthermore it is hard to

see how fish caught in the strong ebb currents associated with power generation are either

able to detect the fish pass or to reach it unless approaching from the northern shore.

Both the Moncton and Windsor causeways provide useful analogues to explain how barrages

created towards the head of an estuary might be expected to change sedimentation patterns. These

analogues are different from a multi-turbine barrage however because the thalweg in these two

examples has been comprehensively altered and tidal energy significantly reduced on both the flood

and ebb tides. Within these two systems, however, tidal propagation means that sediment-laden

water is drawn towards the causeway and provided slack water in which to deposit its load. It seems

unlikely that a tidal barrage will behave in quite the same way, but a plausible thesis might be an

increase in the volume of sandbars both above and below small barrages where sediment

availability is unconstrained.

CONCLUSIONS

6.12. No evidence was gathered that in any way confirms the thesis that the headpond within a

Severn tidal barrage would evolve in an accretionary manner. If such evidence exists it is not

obvious either within the Bay of Fundy or the Eastern Schelde where the majority of

examples of morphological engineering are evolving.

6.13. All of the evidence from the headponds at Annapolis Royal, Moncton and Windsor points to

the fundamental importance of wind-driven waves as the main pathway driving foreshore

evolution in a post-barrage environment. Slumping of rock-armour in some localities close to

the outfalls of the turbines probably relates more to the impact of strong currents and the very

minimalist approach to rock armour engineering employed. It cannot be used as direct

evidence of what might happen in a post-barrage English estuary. It is, however, illustrative of

the problem of progressive sub-tidal bank failure that is likely to occur as steep banks rotate in

response to wind-driven wave erosion under stormy conditions.

6.14. Annapolis Royal and the headponds at Moncton and Windsor are all comparatively small –

several orders of magnitude smaller than that likely to result from a tidal barrage along the

Cardiff-Weston line proposed for the Severn Estuary. Consequently, no comfort can be

derived from the relatively short timescale involved in the re-imposition of something

approaching equilibrium morphology (for wind driven waves) within the Annapolis

headpond. This headpond is tiny in comparison with the likely headpond created by a tidal

barrage on any of the major English estuaries for which proposals exist, and the fetch is also

comparatively small. Rather, this model suggests that the models provided by the Eastern

Schelde and the Regime model for the Severn Estuary are correctly indicative of the potential

scale of erosion problems.

7. REFERENCES & BIBLIOGRAPHY

Canadian Power Group Ltd (CAPG), 1982. Annapolis tidal headpond erosion study: final report for

tidal power corporation. (Not accessed).

Curran, K.J., Milligan, T,G., Bugden, G., Law, B. and Scotney, M.D., 2005. The effects of large-

scale barriers in rivers of the Bay of Fundy: observations from the Petitcodiac river, New

Brunswick. In J. A. Percy, A. J. Evans, P. G. Wells, and S. J. Rolston. (Eds.). 2005. The Changing

Bay of Fundy - Beyond 400 Years. Proceedings of the 6th Bay of Fundy Workshop, Cornwallis,

Nova Scotia, September 29 – October 2, 2004. Environment Canada–Atlantic Region, Occasional

Report No. 23, Environment Canada, Dartmouth, Nova Scotia and Sackville, New Brunswick, 480

pp. + xliv. Page 126.

Daborn, G. 1997. Sedimentological processes. In Greenberg, D.A., Petrie, B.D., Daborn, G.R. &

Fader, G.B. Chapter two: the physical environment of the Bay of Fundy. In Percy, J.A., P.G. Wells

& A.J. Evans (Eds), 1997. Bay of Fundy Issues: a scientific overview. Workshop proceedings,

Wolfville, N.S., January 29 to February 1, 1996. Environment Canada – Atlantic Region Occasional

Report No 8. Environment Canada, Sackville, New Brunswick, 191pp.

Department of the Environment and Local Government for the Province of New Brunswick and

Fisheries and Oceans Canada, 2002. Guidelines for an Environmental Impact Assessment:

modification to the Pettitcodiac River causeway. 38pp. http://www.gnb.ca/0009/0377/0002/0006-

e.pdf Accessed 02 November 2008.

Fisheries and Oceans Canada. B-MAR-01-02d, Petitcodiac River Causeway. http://www.mar.dfo-

mpo.gc.ca/communications/maritimes/back01e/B-MAR-01-02.htm Accessed 02 November 2008.

Hicklin, P.W., 2005. Returning visitors: semipalmated sandpipers in Shepody Bay. In J. A. Percy,

A. J. Evans, P. G. Wells, and S. J. Rolston. (Eds.). 2005. The Changing Bay of Fundy - Beyond 400

Years. Proceedings of the 6th Bay of Fundy Workshop, Cornwallis, Nova Scotia, September 29 –

October 2, 2004. Environment Canada–Atlantic Region, Occasional Report No. 23, Environment

Canada, Dartmouth, Nova Scotia and Sackville, New Brunswick, 480 pp. + xliv. Pages 114-118.

Jones, F.H., 1994. Barrage developments in the Welsh region: the role of the National Rivers

Authority in protecting the aquatic environment. Journal of the Institution of Water and

Environmental Management 8(4): 432-439.

Kirby, R. & Shaw, T.L., 2005. Severn Barrage, UK – environmental reappraisal. Engineering

sustainability 158, issue ESI: 31-39.

MacFarlane Pierce, K., 2007. Evaluation of lateral riverbank movement along the Annapolis River,

Nova Scotia (1955-1996). (Not accessed apart from map).

MARTEC Ltd, 1980. Annapolis tidal power project: report to tidal power corporation. (Not

accessed).

MARTEC Ltd, 1987. Annapolis tidal power project headpond ersion assessment. Report for Nova

Scotia Power, unpublished. 54pp.

Morand, C. & Heralampides, K.A., 2006. Numerical modelling of tidal barrier modification

alternatives: Petitcodiac river case study. Canadian Water Resources Journal Summer, 2006.

http://findarticles.com/p/articles/mi_7111/is_2_31/ai_n28428346?tag=artBody;col1 Accessed 02

November 2008.

Morris, R.K.A., (in press). The impact of tidal energy barrages on estuarine geomorphology. In …

(ed) ………………………………………….. Nova Publishers.

Niles, E., 2001. Review of the Petitcodiac River Causeway And Fish Passage Issues. Report

prepared for Minister of Fisheries and Oceans Canada. http://www.petitcodiac.com/niles-e.pdf

Accessed 02 November 2008.

Oswalt, N.R. & Patrick, D.M., 1999. Bank erosion and instability on the Annapolis River, Nova

Scotia. Report for Nova Scotia Power Ltd. Unpublished. vi + 61 pp (+ appendices).

Percy, J.A., 2008. The “Cause” in the Causeway: crossing the Avon River at Windsor. Fundy Issues

28. 12 pages. Bay of Fundy Ecosystem Partnership.

http://www.bofep.org/PDFfiles/fundy_issue_28.pdf

Pethick, J.S., Morris, R.K.A. & Evans, D.H., (in press). Nature conservation implications of a

Severn tidal barrage – a preliminary assessment of geomorphological change. Journal for Nature

Conservation.

Proosdij, D. van, Daborn, G.R. & Brylinski, M., 2004. Environmental Implications of expanding

the Windsor Causeway (Part 2): comparison of the 4 and 6 lane options. Report prepared for Nova

Scotia Department of Transportation and Public Works. Contract No. # 02-00026. ACER Report

No 75. 18 pages.

Wikipedia website. http://en.wikipedia.org/wiki/Petitcodiac_River Accessed 02 November 2008.

O’Reilly, C.T., Ron Solvason, R. & Christian Solomon, C., 2005. Resolving the world’s largest

tides. In J. A. Percy, A. J. Evans, P. G. Wells, and S. J. Rolston. (Eds.). 2005. The Changing Bay of

Fundy - Beyond 400 Years. Proceedings of the 6th Bay of Fundy Workshop, Cornwallis, Nova

Scotia, September 29 – October 2, 2004. Environment Canada–Atlantic Region, Occasional Report

No. 23, Environment Canada, Dartmouth, Nova Scotia and Sackville, New Brunswick, 480 pp. +

xliv. Pages 153-157.

8. APPENDIX 1 – SUMMARY OF SITE VISITS

Geomorphological unit Sites

Atlantic coast

Mahone Bay

Lunenberg Harbour & Back-harbour

La Have Estuary

Medway Harbour

Outer Bay of Fundy

Digby to Long-Island

Digby Gap

Port Royal

Annapolis Royal

Annapolis Valley Annapolis Headpond

Annapolis River

Minas Basin and Copequid Bay

Wolfville Harbour basin

Windsor Causeway & basin

Windsor to Truro shore

Truro to Parrsbro shore

Avon Valley Wolfville headpond

Avon River

Minas Channel Cape D’or

Advocate Harbour

Chignecto Bay

Amherst to Parrsbro

Joggins Cliffs

Xxxx Cliffs

Pettitcodiac River Moncton Causeway

Riverview causeway