Nature of Impact Duration of Can impact be Will ...

EIR – Reconstruction of the seawall in front of the Salt Rock Hotel - DC29/0040/08

Nature of Impact Direct Extent Duration of Can impact be Will
(potential) or of Impact prevented/reve irreplaceable
Indirect Impact rsed or resources be
managed? lost?

Concern Direct Local Operational Yes – can be No
phase managed.
regarding knock- (permanent)

on effects on

neighbouring

properties.

Probability Mitigatory Mitigation measure Probability Significance
before Potential after after
mitigation mitigation mitigation

the hotel property. As per WSP

(2010), the dune is not deemed

adequate for protection of the

property from flooding and

erosion. During a storm,

vegetation will be more

susceptible to wash away. The

dune system is more prone to

erosion in contradiction to

reinforced concrete walls. The risk

of flooding could be mitigated by

means of a low wall.

Entrances/access points where

the wall does not protect the

hinterland could be blocked with

sandbags in the event of a major

storm, or can incorporate raised

profiles to limit water entering the

buildings (WSP, 2010).

High High Alternative 1 - The location of the Low Low

headland diffuses energy that can

be reflected off the wall. Design

measures such as the alcoves and

the Enviro Rock bags at each wall

end will also act to mitigate

refraction of energy onto adjoining

properties (as per specialist

reports Appendix 12 & 13). It is

emphasised that this impact is

unlikley as indicated by

specialists. Geocontainer cross-

sections such as revetments at the

wall ends created with 4 ton Enviro

Rock bags and a sawtooth

arrangement of Enviro Rock bags

could be placed along the base of

the wall. This should assist in

minimising wave-induced

turbulence at the base of the

structure at the wall ends.

However, no negative effect on

Page 64 of 112

EIR – Reconstruction of the seawall in front of the Salt Rock Hotel - DC29/0040/08

Nature of Impact Direct Extent Duration of Can impact be Will
(potential) or of Impact prevented/reve irreplaceable
Indirect Impact rsed or resources be
managed? lost?

Probability Mitigatory Mitigation measure Probability Significance
before Potential after after
mitigation mitigation mitigation

neighbouring properties is

expected (WSP, 2009; Subtech,

2008).

Alternative 2 - There is concern

that the multiple changes between

the hard and soft structures along

the length of the property and lack

of continuity will make connectivity

between the structures difficult and

will result in weak points. This

option has the potential to

incorporate all the negative points

of both the hard and soft

structures. There is concern that

this would impact adjoining

properties. However, design

measures such as the alcoves and

the Enviro Rock bags at each wall

end will also act to mitigate

refraction of energy onto adjoining

properties (as per specialist

reports Appendix 12 & 13).

Geocontainer cross-sections such

as revetments at the wall ends

created with 4 ton Enviro Rock

bags and a sawtooth arrangement

of Enviro Rock bags could be

placed along the base of the wall

section.

Alternative 3 - The location of the
headland diffuses energy that can
be reflected off the soft structure.
Gabion baskets with bags can be
used to protect the toe of the berm
created. It is not expected that
there will be any impacts on
neighbouring properties.

Alternative 4 – The location of the

Page 65 of 112

EIR – Reconstruction of the seawall in front of the Salt Rock Hotel - DC29/0040/08

Nature of Impact Direct Extent Duration of Can impact be Will
(potential) or of Impact prevented/reve irreplaceable
Indirect Impact rsed or resources be
managed? lost?

Alternative 1: Indirect Local, Operational Yes – can be No
Indirect phase managed.
Positive Impact. A however (permanent)

possible increase potential

in tourists visiting regional

the Salt Rock impact

Hotel and the Salt dependin

Rock area in g on the

general due to the scale of

improved the

appearance of the impact

beach and rock on the

tidal pool area. local

This may result in economy

an increase in

employment

opportunities for

hotel staff and

supporting

industries.

Alternative 2, 3

and 4: May have

indirect impacts

on tourism and

beach users.

Alternative 1: Local Operational No – cannot be No
phase managed.
Potential failure of (permanent)

the wall during a

future storm event

of the same

magnitude as the

March 2007 storm

- A seawall could

pose a risk (in

terms of

introducing

rubble) to the

Probability Mitigatory Mitigation measure Probability Significance
before Potential after after
mitigation mitigation mitigation

headland diffuses energy. It is not Low Low

expected that there will be any

impacts on neighbouring

properties (WSP, 2010).

High High Alternative 1 – Positive impact no

mitigation required. The beach is

an important tourist destination

and as such aesthetics, cultural

appeal and beach space as well

as accessibility and usability by

beach goers is an important

feature in order to retain its

ongoing popularity of the Salt

Rock Hotel.

Alternative 2, 3 and 4 - This
impact can be mitigated. The hotel
can be promoted by many different
marketing strategies and projects
such as competitions and specials
for hotel guests. However, any
structure that reduces available
beach space, negatively impacts
on the visual appeal or cultural /
sense of place that the beach front
currently has could impact on
tourism for the area and the hotel.

High High Alternative 1 - Failure of the Low Low
Page 66 of 112
existing wall may have been

promoted at access points

(stairways). The new design of

these must allow for

concentrations in wave run-up.

Alternatively light timber stairways

could be designed which would be

replaceable after major storms

(WSP, 2009; Subtech, 2008).

Soils behind the wall absorb water

resulting in pressure exerted

EIR – Reconstruction of the seawall in front of the Salt Rock Hotel - DC29/0040/08

Nature of Impact Direct Extent Duration of Can impact be Will
(potential) or of Impact prevented/reve irreplaceable
Indirect Impact rsed or resources be
managed? lost?

adjoining after
properties
failure.

Alternative 2:

Potential failure of

the “mixed”

structure during a

future storm event

of the same

magnitude as the

March 2007

storm. Could pose

a risk (in terms of

introducing

rubble) to the

adjoining

properties after

failure.

Alternative 3:

Potential failure of

the “soft” structure

during a future

storm event of the

same magnitude

as the March

2007 storm.

Alternative 4:

Potential failure of

the dune during a

future storm event

of the same

magnitude as the

March 2007

storm.

Probability Mitigatory Mitigation measure Probability Significance
before Potential after after
mitigation mitigation mitigation

against the seawall. In the case of
concrete or hard structures, this
back pressure may cause the
seawall to constantly move
forward can be managed by the
use of a wide concrete footing
and/or the use of tie backs or
cables connecting the seawall
structure to a stable area behind it.
The seawall should also be
backfilled with crushed rock to
allow free drainage trough the
reinforced zone or fill zone behind
the seawall. A well-designed
reinforced concrete wall founded
on bedrock is less likely to fail than
a geobag structure. In addition, a
well-designed reinforced concrete
wall should be less likely to fail
during a storm event than a gabion
wall or an interlocking block wall. If
the structure should fail under
these conditions a gabion wall or
an interlocking block wall are more
likely to break up into fragments
which can easily be transported by
wave action (Subtech, 2008 &
WSP 2009). Reinforced concrete
walls are not prone to progressive
failure as is the case with gabions/
interlocking block/ geobag walls.

Alternative 2 – Mitigation

measures for alternative 1 can be

used for the hard wall sections of

the structure. Mitigation measures

for alternative 3 can be used for

the “soft” sections of the structure.

Repair of the wall / soft structure

hybrid solution would be

complicated and require varied

Page 67 of 112

EIR – Reconstruction of the seawall in front of the Salt Rock Hotel - DC29/0040/08

Nature of Impact Direct Extent Duration of Can impact be Will
(potential) or of Impact prevented/reve irreplaceable
Indirect Impact rsed or resources be
managed? lost?

CULTURAL Direct Local Construction Yes – can be No
Potential phase prevented.
unearthing and

Probability Mitigatory Mitigation measure Probability Significance
before Potential after after
mitigation mitigation mitigation

and costly construction

techniques.

Alternative 3 - Geobag structures

are prone to progressive failure in

contradiction to reinforced

concrete walls. This is a major

and significant problem with

regards the affordability of

protecting the property.

Unsightly waste would be created

if the structure were to be

destroyed. However, this should

not be difficult to clean. Bags can

be removed and replaced. Sand

needs to be obtained from the

beach itself if this is available,

otherwise sand will need to be

imported from a registered source

which should preferably be similar

to existing sand (WSP, 2009;

Subtech, 2008). Coastal property

owners should prepare for erosion

events by purchasing and storing

appropriate sand bags (Breetzke,

2008). However, it may increase

the risk of introducing waste to

neighbouring properties if the

structure were to be destroyed.

(WSP, 2009; Subtech, 2008).

Imported sand would need to be

approved by a specialist.

Alternative 4 – No mitigation
required. As per the WSP report
(2010), no impacts are expected
from a coastal processes point of
view on neighbouring properties.

Low High A Heritage Impact Assessment Low Low
has been conducted and has been Page 68 of 112

EIR – Reconstruction of the seawall in front of the Salt Rock Hotel - DC29/0040/08

Nature of Impact Direct Extent Duration of Can impact be Will
(potential) or of Impact prevented/reve irreplaceable
Indirect Impact rsed or resources be
damage to items (short-term) managed? lost?
of cultural or
historical
significance.

Alternative 1: Direct Local Operational No – cannot be No
phase prevented.
Retain sense of (permanent)

place as the wall

is an important

identifying feature

for the area.

Alternative 2:

Partial loss of

sense of place

with retention of

only part of the

wall which is an

important

identifying feature

for the area.

Alternative 3 and
4: Loss of sense
of place as the
wall is an
important
identifying feature
for the area.

Probability Mitigatory Mitigation measure Probability Significance
before Potential after after
mitigation mitigation mitigation

included in Appendix 2. As per the

Heritage Impact Assessment the

a single potsherd on the beach

indicate that the coastal dunes

must have formerly been inhabited

by Early Iron Age man, as such

communities did exist at Salt

Rock. During the process of

foundation trenches being dug for

the wall, any potsherds surfacing

should be collected and deposited

with AMAFA.

No No Alternative 1 - No mitigation No No mitigation
mitigation mitigation mitigation required
required required required. However, the wall is required

around 70 years old and therefore

has cultural significance and

meaning for the sense of place

and identity of the area and hotel.

As per the Heritage Impact

Assessment (Appendix 2) the

existing damaged seawall was

built from stone and mortar in the

early 20th century. As such, these

structures are protected by

Heritage Legislation and may not

be destroyed or altered without

obtaining the necessary permit

from the appropriate authorities.

Alternative 2 - This impact cannot
be mitigated. However, at least
part of the wall with its historic
significance to the hotel will be
retained.

Alternative 3 and 4 - This impact
cannot be mitigated. The seawall
has been in place at least 70 years
and is seen as a cultural landmark
for the hotel, caravan park and
tidal pool.

Page 69 of 112

EIR – Reconstruction of the seawall in front of the Salt Rock Hotel - DC29/0040/08

Nature of Impact Direct Extent Duration of Can impact be Will
(potential) or of Impact prevented/reve irreplaceable
Indirect Impact rsed or resources be
Alternative 1: Operational managed? lost?
Direct Local phase No
(permanent) No – cannot be
Will retain and prevented.

repair a culturally

significant feature

(wall).

Alternative 2:

Will retain and

repair at least part

of a culturally

significant feature.

Alternative 3 and
4: Loss of a
culturally
significant feature
(wall).

IMPACTS OF THE NO-GO OPTION

The existing Direct Local Operational No – cannot be No
phase managed.
damaged seawall (permanent)

may continue to

degrade over

time. The current

state of the site

will allow for

further backward

eroding of the

property and

degradation in the

general

Probability Mitigatory Mitigation measure Probability Significance
before Potential after after
mitigation Cannot be Alternative 1 – Cannot be mitigation mitigation
Cannot be mitigated
mitigated mitigated. However, the wall is Cannot be Cannot be
Medium mitigated mitigated
High
around 70 years old and therefore

has cultural significance and

meaning for the sense of place

and identity of the area and hotel.

As per the Heritage Impact

Assessment (Appendix 2) the

existing damaged seawall was

built from stone and mortar in the

early 20th century. As such, these

structures are protected by

Heritage Legislation and may not

be destroyed or altered without

obtaining the necessary permit

from the appropriate authorities.

Alternative 2 - This impact cannot
be mitigated. However, at least
part of the wall with its historic
significance to the hotel will be
retained.

Alternative 3 and 4 - This impact
cannot be mitigated. The seawall
has been in place at least 70 years
and is seen as a landmark for the
hotel, caravan park and tidal pool.

Rehabilitation is required due to Low Low

the current state of the proposed

site. The “brush wood” dune

system currently established in

front of the Salt Rock Hotel is

intended to be a temporary

measure. A long term measure is

therefore needed to retain the

frontal slopes/banks of the hotel

property which is both

aesthetically pleasing and does

not significantly impact the

Page 70 of 112

EIR – Reconstruction of the seawall in front of the Salt Rock Hotel - DC29/0040/08

Nature of Impact Direct Extent Duration of Can impact be Will
(potential) or of Impact prevented/reve irreplaceable
Indirect Impact rsed or resources be
managed? lost?
Direct Local No
appearance of the
No
Salt Rock Hotel
No
and the Salt Rock

beach in general

(Subtech, 2008).

Potential failure of Operational No – cannot be
phase managed.
the remaining (permanent)

structure during a

future storm event

of the same

magnitude as the

March 2007

storm. Could pose

a risk (in terms of

introducing

rubble) to the

adjoining

properties after

failure.

There may be an Direct Local Operational Yes – can be
Indirect phase managed.
increase of (permanent)

trespassers

entering the

property, this may

particularly have a

negative impact

on guests using

the facilities at the

caravan park.

A possible Local, Operational Yes – can be
phase managed.
decrease in however (permanent)

tourists visiting potential

the Salt Rock regional

hotel and the Salt impact

Rock area in dependin

general due to the g on the

degraded scale of

appearance of the the

beach and rock impact

tidal pool area. on the

Probability Mitigatory Mitigation measure Probability Significance
before Potential after after
mitigation environment. This impact can mitigation mitigation
therefore be mitigated by adopting
either alternative 1, 3 or 4.

Cannot be Cannot be Cannot be mitigated. There is Cannot be Cannot be
mitigated mitigated mitigated mitigated
concern that the multiple changes
Low Low
between the hard and soft

structures along the length of the

property and lack of continuity will

make connectivity between the

structures difficult and will result in

weak points. This option has the

potential to incorporate all the

negative points of both the hard

and soft structures. There is

concern that this would impact

adjoining properties and therefore

alternative 1, 3 or 4 should be

adopted.

High Low A fence can be constructed to

restrict access to the hotel

property. However, there is the

possibility that this may be

unsightly and could impact the

sense of place and look of the

Hotel.

High Medium This impact can be mitigated. The Low Low
Page 71 of 112
hotel can be promoted by many

different marketing strategies and

projects such as competitions and

specials for hotel guests.

However, the wall cannot be left in

its current state as damaged areas

will ultimately be re-introduced

onto the beach and sea

environment. Some form of

rehabilitation will be required.

EIR – Reconstruction of the seawall in front of the Salt Rock Hotel - DC29/0040/08

Nature of Impact Direct Extent Duration of Can impact be Will
(potential) or of Impact prevented/reve irreplaceable
Indirect Impact rsed or resources be
managed? lost?
local
This may impact economy

the viability of the

operation of the

hotel. This may

result in a

decrease in

employment

opportunities for

hotel staff and

supporting

industries.

Probability Mitigatory Mitigation measure Probability Significance
before Potential after after
mitigation mitigation mitigation

Page 72 of 112

EIR – Reconstruction of the seawall in front of the Salt Rock Hotel - DC29/0040/08

From the assessment of impacts identified, key impacts as a result of the applicants preferred alternative
(Alternative 1) relate to potential knock on effects on neighbouring properties (although unlikely and
insignificant), protection of the property from trespassers and flooding, as well as possible impacts on the coastal
processes. These impacts are of low significance provided that all mitigation measures are adhered to.

There is a potential for the seawall to cause damage to neighbouring properties should the wall fail during a future
storm event of the same magnitude as the March 2007 storm - A seawall could pose a risk (in terms of introducing
rubble) to the adjoining properties after failure. The preferred alternative (alternative1) will entail construction of a
well-designed reinforced concrete wall founded on bedrock and will be less likely to fail than a geobag structure
(alternative 3) which could litter the beach if the structure is destroyed. Reinforced concrete walls are not prone to
progressive failure as is the case with gabions/ interlocking block/ geobag structures. Failure of the existing wall
may have been promoted at access points (stairways). The design of these must allow for concentrations in wave
run-up. Alternatively light timber stairways could be designed which would be replaceable after major storms
(WSP, 2009; Subtech, 2008). Soils behind the wall absorb water resulting in pressure exerted against the seawall.
In the case of concrete or hard structures, this back pressure may cause the seawall to constantly move forward
can be managed by the use of a wide concrete footing and/or the use of tie backs or cables connecting the seawall
structure to a stable area behind it. The seawall should also be backfilled with crushed rock to allow free drainage
trough the reinforced zone or fill zone behind the seawall. As per the specialist reports in Appendix 12 and 13,
design measures such as the alcoves and the enviro rock bags at each wall end can act to mitigate refraction of
energy onto adjoining properties (although this impact is unlikely anyway). Geocontainer cross-sections such as
revetments at the wall ends created with 4 ton Enviro Rock bags and a sawtooth arrangement of Enviro Rock bags
could be placed along the base of the wall. This should assist in minimising wave-induced turbulence at the base of
the structure at the wall ends. However, no negative effect on neighbouring properties is expected (WSP, 2009 &
2010; Subtech, 2008).

With regards to protection of the property, the seawall will restrict access from the beach to the hotel when
repaired. The wall also protects the property from further backward erosion (Subtech, 2008). The report by WSP
(2010) has also confirmed that the seawall will serve to protect the property and lower flats of the hotel from
flooding over the long term. Excessive wave overtopping can be mitigated by raising the wall and/or to incorporate
a recurve within the wall. Alternatively, wave overtopping could be reduced by locating the wall further landward
(WSP, 2010).

The key impacts and mitigations on the coastal processes are therefore:

Impact on Littoral Drift:
 This is naturally mitigated as discussed in preceding sections. According to WSP, “During normal sea
conditions, the seawall will at most be either on land or only just encroaching on the inner surf zone, and
thus no effects on littoral drift are anticipated. This view is supported by Subtech (2008).”

Refraction / Reflection of wave energy:
 Wave fronts are significantly deflected by the headland (Subtech).
 Reflected waves will be rapidly dispersed, generally offshore, and thus no effect on the local beach profile
is foreseen from this mechanism (WSP).
 Due to the undulating shape of the wall the reflected waves will be scattered and impact reduced
(Subtech).
 Any waves reflected in a potentially harmful direction (i.e. not offshore where no harmful effect could occur)
will be dispersed, through the process of wave diffraction (lateral spreading of wave energy), refraction and
bottom friction, and it is deemed that no negative effect on neighbouring properties will ensue (WSP).
 The concept of reflection causing erosion seaward of a seawall is a commonly accepted hypothesis.
However, more recent literature (e.g. referred to in Ruggerio et al, 2001) casts doubt on this hypothesis,
which in any event is not associated with a clear physical explanation. In addition, recent computation
modelling studies of beach erosion indicate no difference in beach change with and without reflection
included in the model (McDougal et al., 1996).
 The wall should be angled between 27°and 35°, this will further reduce wave energy.

Localised Scour (during extreme storm conditions):
 During elevated water levels, storm wave-induced turbulence at the base of the seawall, complemented by
lack of supply from dune erosion (indicated in 3.2) will probably cause localised scour. At the ends of
seawalls “flanking” effects, i.e. localised increased erosion, can be expected. Both of these effects are
cited by Dean (1986) and Basco (2004; WSP, 2009).

Page 73 of 112

EIR – Reconstruction of the seawall in front of the Salt Rock Hotel - DC29/0040/08

 For this reason measures such as the proposed geocontainer cross-sections, as referred to in Subtech
(2008) may be an advisable mitigation measure (WSP).

 The northbound alongshore flow of water that originates from overtopping of the headland would, as
indicated in Subtech (2008) occur regardless of whether the seawall is present or not. However this flow is
most likely concentrated somewhat through the constricting effect of the seawall and may also promote
localised scour (WSP).

 The shape of the northern wall termination should be modified to provide substantial roughness which will
act as en energy diffuser and slow down the long shore current during storm conditions. Minor scour of
sand is expected to occur at the base of the wall and at the ends of the seawall. It is recommended that
appropriate mitigation for the latter be considered, such as an appropriate geobag design (similar to that
indicated in Subtech, 2008) or allowance for a degree of retreat. Appropriate tie-back of the seawall into
the hinterland at the wall ends should be part of the seawall design.

 Construction of alcoves with a 4-5m setback will further reduce scour potential. These will reflect the wave
fronts in random patterns and retard the flow along the wall thereby reducing the wash onto the adjoining
beaches.

 A “toe” to be constructed as part of the foot of the wall to be laid on the bedrock as per the engineering
drawings provided (Appendix 9).

 The wall ends should be combined with Enviro Rock bags. The seawall would be constructed to come to
an end behind a revetment created with 4 ton Enviro Rock bags and a sawtooth arrangement of Enviro
Rock bags would be placed along the base of the wall (WSP, 2009; Subtech, 2008).

Integrity of the structure
 The integrity of a reinforced concrete structure which is designed appropriately will preclude the possibility
of introducing building rubble to the nearshore region (WSP);
 If designed appropriately, the seawall will be effective in protecting the hotel property (WSP).
 Soils absorb water resulting in pressure exerted against the seawall. In the case of concrete or hard
structure seawalls the back pressure may cause the seawall to constantly move forward. This can be
sustained by the use of a wide concrete footing and/or the use of tie backs or cables connecting the
seawall structure to a stable area behind it. The seawall should be backfilled with crushed rock to allow free
drainage through the reinforced zone or fill zone behind the seawall (WSP, 2009; Subtech, 2008).

Beach profile
 Inland sand supply is deemed to be negligible (Subtech). Under extreme storm conditions the wall will
prevent a small volume of sand from entering the sea, such that it will not be available to build an off shore
sand bar (Subtech).
 According to WSP, an impact on the beach profile can be expected as a result of the “denial” of sand
supply from erosion that would otherwise occur with a natural beach or (to a lesser degree) with a hidden
soft defence. A suitable mitigation would thus simply be post-storm replenishment of sand (of suitable
grain size distribution) which would have been naturally “supplied” during the storm, should a more set-
back or “soft” solution have been employed (Dean, 1986). Such mitigation measures are employed in the
USA (Basco, 2004).
 Should this become necessary, the required sand supply could be estimated through the monitoring of
nearby profiles (that incorporate appropriate set-back soft solutions) experiencing similar wave conditions
by means of regular surveys. The amount of sand denied during storm erosion can be estimated from pre-
and post-storm surveys and this volume should then be supplied to the beach zone – preferably in eroded
areas where it is most needed. Alternatively the amount of sand supply required could be estimated by
means of a calibrated storm erosion model (WSP).

From the assessment of impacts identified, key impacts as a result of the EAP’s preferred alternative
(Alternative 2) relate to localised scour, the potential erosion of neighbouring properties and the potential safety
risk that may arise as a result of overtopping (although specialists have stated that this is unlikely). These impacts
are of low significance provided that all mitigation measures are adhered to. The positive and negative impacts
for both the hard (alternative 1) and soft structure (alternative 3) alternatives will generally apply to this
alternative.

The primary positive impact of this option is the protection of hotel property and the lower flats of the hotel in the
long-term, this impact is considered to have a high significance.

The hybrid structure has the following advantages over alternative 1:

Page 74 of 112

EIR – Reconstruction of the seawall in front of the Salt Rock Hotel - DC29/0040/08

o The northern and southern ends of the coastal protection are composed of sloped sand-bag sections which are
tied back into the hinterland. This design will mitigate against flanking erosion effects on neighbouring
properties (in the unlikely event of any impact being caused on these properties);

o The sloped sandbag protection sections will:
 Allow for planting of vegetation;
 Promote the accumulation of windblown sand, this accumulated sand will serve as a buffer (as additional
protection) during storms; and will have a more natural appearance when vegetated.
 The design allows for easy retreat (e.g. should this be required in the event of severe sea-level rise) in
parts (WSP, 2012).

Based on the specialist study conducted, the primary negative impacts of the proposed hybrid coastal protection
structure are (WSP, 2012):

1. Localised additional scour (relative to a natural dune profile) and consequent localised beach lowering
(predicted to be a maximum of roughly 0.5 m over a 20 m section of the beach) during major storms. This
impact is considered to have a low significance, considering that the erosion will be mitigated through the
sand accumulated on the sandbag slope and considering that the eroded sand will be returned via natural
processes.

2. Possible aggravation of erosion of neighbouring properties, as indicated by documented mechanisms.
However this impact is also considered to have a low significance due to indications of minimal impact to
neighbouring properties via computational modelling and aerial photography analysis.

3. The reduction of the hotel grounds (lawn) area. This impact cannot be mitigated as there will be a loss of
area for the applicant.

4. Temporary danger to pedestrians related to wave overtopping. The hotel should take the responsibility of
warning guests by posting a guard and/or fencing off the shoreward region and/or erecting signage, during
wave overtopping events.

WSP Africa Coastal Engineers have provided comment on the engineering aspects of the structure (Appendix 9), it
is recommended that these comments / recommendations be addressed in the final design should the hybrid
option be approved. However please note that the refinements in the design are not considered to be part of this
EIA specialist study, since no significant change to the structure geometry is anticipated. It is assumed for the
purpose of this EIA specialist study that both the seawall (including hidden sections) and the sand-bag sections will
ultimately be designed according to best coastal engineering practice (WSP, 2012). As a result of these
advantages the hybrid design, if designed appropriately, would be considered preferable to the “seawall
only” (alternative 1) option as evaluated in 2012 WSP specialist report (Appendix 9).

From the detailed investigation into potential impacts provided in Table 9, it is evident that all impacts can either be
mitigated or prevented. Construction impacts will be managed through the site specific EMPr (Appendix 4).

6.3 Draft Environmental Management Programme [Regulation 31 (2) (p) and 33]

A draft environmental management programme (EMPr) in accordance with regulation 33 has been compiled and is
included in Appendix 4.

6.4 Determination and Assessment of Cumulative impacts [Regulation 32 (2) (l) (i)]

The NEMA EIA regulations define cumulative impact as follows:

“in relation to an activity, means the impact of an activity that in itself may not be significant but may become
significant when added to the existing and potential impacts eventuating from similar or diverse activities or
undertakings in the area;”

The DEA guideline on the assessment of alternatives and impacts identifies two types of cumulative impacts:

(1) Additive cumulative impact, i.e. where the identified potential impact adds to the impact which is caused by
other similar impacts; or

(2) Interactive cumulative impact, i.e. where a cumulative impact is caused by different impacts that combine
to form a new kind of impact. Interactive impacts can be further classified:

a. Counterveiling: the net adverse cumulative impact is less than the sum of the individual impacts; or

b. Synergistic: the net adverse cumulative impact is greater than the sum of the individual impacts

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EIR – Reconstruction of the seawall in front of the Salt Rock Hotel - DC29/0040/08
Table 10 provides an assessment of potential cumulative impacts that may arise from the development proposal:

Table 10: Assessment of Potential Cumulative Impacts

Nature Of Impact Alternative 1 - Ongoing revenue generated from the tourism industry in the Salt Rock area
positively influencing the local economy over the long term.
Extent Of Impact Local & Potential regional impact
Duration Of
Impact Operational / built phase
Type of
Cumulative Interactive Cumulative
Impact
Mitigatory Positive impact, no mitigation required.
Potential
The wall will retain easy use of this popular beach by beach goers and ensure ongoing aesthetic appeal,
Mitigation retention of structure of cultural significance and protection of the hotel property. The wall will maximize
Measure available beach space for users. The beach is an important tourist destination and as such aesthetics,

Probability after cultural appeal and beach space as well as accessibility and usability by beach goers is an important
mitigation feature in order to retain its ongoing popularity.

Significance after N/A
mitigation
N/A
Nature Of Impact
Alternative 2, 3 and 4 - Potential negative impact on revenue for the Salt Rock area and hotel if
Extent Of Impact beach use is negatively impacted.
Duration Of Local & Potential regional impact
Impact
Type of Operational / built phase
Cumulative
Impact Interactive Cumulative
Mitigatory
Potential Medium

Mitigation The hotel can be promoted by many different marketing strategies and projects such as competitions and
Measure specials for hotel guests. However, any structure that reduces available beach space, negatively impacts

Probability after on the visual appeal or cultural / sense of place that the beach front currently has and could impact on
mitigation tourism for the area and the hotel.

Significance after Medium
mitigation
Medium
Nature Of Impact
Extent Of Impact Reduction of sand being fed to beaches to the north.
Local & Potential regional impact
Duration Of
Impact Operational / built phase
Type of
Additive
Cumulative
Impact Medium

Mitigatory Alternative 1 –
Potential A suitable mitigation recommended by the Specialist WSP (2010) would be post-storm replenishment of
sand (of suitable grain size distribution) which would have been naturally “supplied” from the dune during
Mitigation the storm, should a dune solution have been employed (as suggested by Dean, 1986). The required sand
Measure
supply could be estimated through the monitoring of nearby profiles (that incorporate appropriate set-
back soft solutions) experiencing similar wave conditions by means of regular surveys. The amount of
sand denied during storm erosion can be estimated from pre- and post-storm surveys and this volume

should then be supplied to the beach zone – preferably in eroded areas where it is most needed.
Alternatively the amount of sand supply required could be estimated by means of a calibrated storm
erosion model. It is assumed that supply would be conducted such that impacts during the process are
negligible. An alternative mitigation would be to establish the seawall further landward. However, over the
past 70 years, there has been a steady sand supply carried around the headland on to the northern
beaches by longshore drift from the more southerly beaches. According to a CSIR study on the shoreline
accretion predictions in the Durban Bight, the Durban sand bypass scheme will increase sand supply

from 270 000 cubic meters per year to 500 000 cubic meters per year and under this new bypass
scheme, it is predicted that over the next twenty years, there will be a net increase in accretion of

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