Present Day Climate Change2 year 0 050 year 0 12100 year 0 12200 year 5 14

Present Day Climate Change2 year 0 650 year 6 11100 year 7 12200 year 7 13

Present Day Climate Change2 year 1 2350 year 25 57100 year 26 67200 year 26 77

Present Day Climate Change2 year 0 1750 year 18 65100 year 29 79200 year 35 83

Present Day Climate Change2 year 0 050 year 2 56100 year 2 63200 year 9 69

Rhu

Return PeriodProperty Count

West Clyde Street

Return PeriodProperty Count

Sailing Club

Return PeriodProperty Count

Craigendoran

Return PeriodProperty Count

East Clyde Street

Return PeriodProperty Count

Total Score Summary comments

1 Do nothing 31

No maintenance of existing defences. Does not meet technical requirements and is detremental to all social, political and legal factors. ABC are required to maintain existing defences.

2 Do minimum 37

Maintain existing defences. ABC are required to maintain existing defences. This will provide the baseline against which further options will be tested.

3 New sea wall 40

A new wall could be built of concrete, steel piles or masonry. This option would seek to replace the existing defence, or could be placed seaward of the existing defence in order to advance the line. To adapt to climate change, the wall would need to be taller than the current defence.

This option seeks to replace the existing sea wall and can achicve the technical requirements without compromising on social, environmental, political and legal factors. Beach access can be maintained and the footprint of the 'hard' structure will be minimal.

4 Raise existing defences 33

Raising the existing defence would increase the flood protection performance of the defence in the short tomid-term. However, as this option relies on the existing structure it can only practically be raised so farwithout a complete re-build. In areas where the existing structures are currently in poor condition aconcrete 'face', 'backing' or 'shroud' could be used to enhance or strengthen the existing defence.

Option discounted as the exisitng wall is in very poor conditon and it can not be raised.

5 Rock armour revetment 33

Rock armour could be installed at the base of the existing defence to increase flood protection performance. This option may or may not include a wall on top.

Option discounted due to the footprint required and restrictions it would place on beach access.

7 New stepped or sloping revetment 35

A new stepped revetment or similar modular blockwork structure could be constructed. All solutions could be designed such that their wave overtopping performance is suitable into the long-term scenario; this may or my not include a wall on top. This option would seek to replace the existing defence, or could be placed seaward of the existing defence in order to advance the line.

Option shortlisted as it can meet the technical requirements at Rhu while not compromising on beach access to the same extent as the rock armour option.

10 Property relocation 22

Properties at immediate flood risk behind the current coastal defences could be relocated, reducing potential flood damages while also providing additional space for flood protection improvement schemes behind the existing defences.

Option not feasable due to significant disruption to social and political factors.

11 Property Flood Resilience and Resistance (PFR) 43

PFR measures could be a valuable option to incorporate into those properties at risk of flooding. This could be in conjunction with automated traffic signs to advise of diversions on roads. Shortlisted option as PFR can provide efficient short-term benefits.

DescriptionOption

Standard of ProtectionShort-termPresent day

to 2030

Mid-termPresent day

to 2070

Long-termPresent day

to 2118

Key reason(s) for shortlisting / discounting Short list options in green

Evaluating coastal flood risk within Helensburgh, Craigendoran and Rhu

Rhu Long List Assessment

Rhu Benefit Zone Overview

The Rhu benefit zone runs from where Gareloch Road turns along the coast in the east to Spys Lane in the west. The existing defences include a masonry wall, gabion baskets and a rock armour revetment; each of these can be seen in the photographs below.

The map shows the modelled flood extents for the Rhu benefit zone for the 2 year event along with the 200 year event under present day conditions and with climate change taken into account.

It can be seen that there is no coastal flood risk during the 2 year event, but for higher return periods coastal water is shown to inundate the main road as well as affecting some properties.

The table below summarises the number of properties that the modelling shows to be at coastal flood risk for a range of different events.

A range of potential options were considered for the Rhu benefit zone; these are detailed within the table on the left. These options were assessed against technical, economic, environmental, social, political and legal criteria, with each category being assigned a score based on whether the option met the aims of the assessment criteria. A summary of the total scores is provided for each option considered, with those taken through to the short list phase for further assessment highlighted in green.

Masonry wall Rock armour revetment Gabion baskets

Rhu Flood Extents

ROCK ARMOUR

TOPSOIL MINIMUM 150mm

ASPHALT

BLINDING

MASONRY WALL

RC CONCRETE

GRANULAR FILL

ST2 CONCRETE TO APPENDIX 26/1

COMPACTED SUB GRADE

WALL OFFSET BY APPROXIMATELY 1.5mTO MINIMISE DISRUPTION TO ROADDURING CONSTRUCTION 5.38mAOD

4.75mAOD1.50m

SECTION A-A (OPTION 1): NEW SEA WALL1:50

VEGETATED EARTH EMBANKMENT

EARTH REINFORCEMENT (e.g. COIRMATS OR EROSION PROTECTION)

MASONRY CLADDING

COPING STONE

EXISTING WALL TO BE DEMOLISHED

ROAD

NEW REINFORCEDCONCRETE WALL

50mm BLINDING

1.00

0.40

2.28

0.50

1.23

4.13mAOD

3.42mAOD

2.18mAOD

NEW ASPHALT PAVEMENT

EXISTING GROUND PROFILE

BEACH

4.76mOD 1 in 200 Year ESL, 2118

SUB BASE

COMPACTED FILL MATERIAL

5.23mAOD

4.75mAOD

SECTION A-A (OPTION 2): NEW SLOPED REVETMENT1:50

1.10

0.40

GEOTEXTILE

ROCK ARMOURSCOUR PROTECTION

CONCRETE KERB TOE

BANK REPROFILED

GEOTEXTILE

100mm GRANULARCOMPACTED SUB-LAYER

CONCRETE BLINDING

EXISTING WALL DEMOLISHED

WALL OFFSET BY APPROXIMATELY 1mTO MINIMISE DISRUPTION TO ROAD.

HILLBLOCK BASISIBLOCK ORSIMICA MODULAR BLOCK.

COPING STONE

0.05

4.13mAOD 41

CONCRETE TOEFOUNDATION

4.76mOD 1 in 200 Year ESL, 2118

ROAD

BEACH

MASONRY CLADDING

NEW REINFORCED CONCRETE WALL

EXTENSION OF ASPHALT ROAD

SUB BASE

2.12mAOD

FORMATION LEVEL

GEOTEXTILE

RHU WALL

DEFENCE TO TIE INTOHIGHER GROUND

A

A

TIE IN DEFENCE EXTENT TO BECONFIRMED IN DETAIL DESIGN.EXISTING ROCK ARMOURDEFENCE OFFERS IMPROVEDFLOOD PROTECTION COMPAREDTO THE REST OF FRONTAGE

434.94m

DRAFT

1

2

No. Construction Risk Maintenance Risk Demolition Risk

In addition to the hazards/risks normally associated with the types of work detailed on thisdrawing take note of the above.

SAFETY, HEALTH AND ENVIRONMENTAL INFORMATIONBOX

RHU

New Wall and Sloped Revetment

2018s0549-JBAU-XX-XX-DR-C-1004

As Shown @ A1

S0 P01.05

The property of this drawing and design vested in Jeremy Benn Associates Ltd. It shall not be reproduced in whole or in part,nor disclosed to a third party, without the prior written consent of Jeremy Benn Associates Ltd.

Project

Title

Clientfor

Unit 2.1Quantum CourtResearch Avenue SouthHeriot Watt UniversityEDINBURGHEH14 4APUnited Kingdom

T +44 (0)131 3192 940E info@jbaconsulting.com

Designed:

Approved:

Drawn:

Checked:

Project Reference: Scale:

Drawing Number: Sheet Size:Status: Revision:

A1

www.jbaconsulting.comTwitter @JBAConsulting

Cowal and Lomond FLRMP

2018s0549

ARGYLL & BUTE COUNCIL

General Notes

A. All dimensions shown are in metres unless otherwise stated and levels in metres toOrdnance Datum.

B. Do not scale from this drawing. All dimensions must be checked/verified on site.C. Any discrepancies noted on site are to be reported to the Supervisor immediately.D. The locations of any known services shown on drawing are approximate and for

guidance only. The Contractor will confirm the location of any services prior to thecommencement of any works.

E. The electronic version of this drawing is not to be used for setting out.F. Refer to Contract Specification for details of materials and workmanship to be used

for the works shown on this drawing.

PLAN1:1000

Drawing Notes

1. This drawing is to be read in conjunction with:-2. Crest heights are post settlement and consolidation. Dimensions and levels are

subject to change.

0 20 20050 100

Key:

Indicative alignment

LEGEND

0.40

2.20

6.22mAOD

SECTION B-B (OPTION 1): 6 NEW WALL1:50

EXISTING CONCRETEWALL TO BE DEMOLISHED

0.3- 1t ROCK ARMOURSOUR PROTECTION

GEOTEXTILE WRAPBELOW ROCK ARMOUR

0.5m BLINDING

GROUND RAISED 1m AT CROSSSECTION 6, WHERE REQUIRED.ALTHOUGH VARIABLE ACROSS

THE SECTION.

EXISTING RECREATIONAL GREEN

4.04mAOD

2.27mAOD

1.50

MASONRY COPING

4.76mOD 1 in 200 Year ESL, 2118

MASONRY CLADDING

BEACH

2.20

0.40

WALL RAISED ALONGEXISTING DEFENCE ASNO ROOM TO SET BACK.

SECTION A-A (OPTION 1) : NEW SEA WALL1:50

1.20

5.60mAOD

NEW WALL DOWELLED INTOEXISTING SEA WALL

MASONRY COPING MASONRY CLADDING 0.40 EXISTING ROAD

EXISTING GROUNDPROFILE

EXISTING SEA WALL INGOOD CONDITION

BEACH

4.76mOD 1 in 200 Year ESL, 21184.53mAOD

EXISTING GROUND

ROCK ARMOUR

TOPSOIL MINIMUM 150mm

BLINDING

EXISTING GROUND LEVEL

RC CONCRETE

GEOTEXTILE

SAILING CLUB WALL

SAILING CLUB

A

A

B

B

67.46

110.44

92.07

101.86

177.61

DRAFT

1

2

No. Construction Risk Maintenance Risk Demolition Risk

In addition to the hazards/risks normally associated with the types of work detailed on thisdrawing take note of the above.

SAFETY, HEALTH AND ENVIRONMENTAL INFORMATIONBOX

Drawing Notes

1. This drawing is to be read in conjunction with:-2. Crest heights are post settlement and consolidation. Dimensions and levels are

subject to change.

Sailing Club New Wall AW

2018s0594-JBAU-XX-XX-DR-C-1001

As Shown @ A1

S0 P01.06

A Coad 19/04/19

The property of this drawing and design vested in Jeremy Benn Associates Ltd. It shall not be reproduced in whole or in part,nor disclosed to a third party, without the prior written consent of Jeremy Benn Associates Ltd.

Project

Title

Clientfor

Unit 2.1Quantum CourtResearch Avenue SouthHeriot Watt UniversityEDINBURGHEH14 4APUnited Kingdom

T +44 (0)131 3192 940E info@jbaconsulting.com

Designed:

Approved:

Drawn:

Checked:

Project Reference: Scale:

Drawing Number: Sheet Size:Status: Revision:

A1

www.jbaconsulting.comTwitter @JBAConsulting

Cowal and Lomond FLRMP

2018s0549

ARGYLL & BUTE COUNCIL

General Notes

A. All dimensions shown are in metres unless otherwise stated and levels in metres toOrdnance Datum.

B. Do not scale from this drawing. All dimensions must be checked/verified on site.C. Any discrepancies noted on site are to be reported to the Supervisor immediately.D. The locations of any known services shown on drawing are approximate and for

guidance only. The Contractor will confirm the location of any services prior to thecommencement of any works.

E. The electronic version of this drawing is not to be used for setting out.F. Refer to Contract Specification for details of materials and workmanship to be used

for the works shown on this drawing.

PLAN1:2000

0 20 20050 100

Aerial plan of proposed extent of flood defences in Rhu.

Not to Scale

Evaluating coastal flood risk within Helensburgh, Craigendoran and Rhu

There are three short listed options for the Rhu benefit zone:

- New sea wall - New stepped or sloping revetment - Property Level Resistance and Resilience

This poster presents details of the two engineered options, with the plan view to the left showing the extent of the potential defences.

A schematic section of the options is then presented below along with some example photographs of this type of defence.

Examples of Property Level Resistance and Resilience are shown in the final poster, with further information also available from the Scottish Flood Forum representative present here today.

Proposed Option 1 - New sea wall Proposed Option 2 - New sea wall and sloped revetment

Please note that this drawing is not to scale and all dimensions and materials are indicative at this stage and may be subject to change prior to final construction.

Please note that this drawing is not to scale and all dimensions and materials are indicative at this stage and may be subject to change prior to final construction.

Section A-A (Option 1) Section A-A (Option 2)

Rhu Options

Example of a stone clad defence wall. Example of a sloping revetment constructed from modular blocks.