MONSON The Saltings, Coast Road, Norman’s Bay, Pevensey, East Sussex

Flood Risk Assessment

Issue A 1 24th April 2016 © Monson Engineering 2016

EXECUTIVE SUMMARY

This report supports a planning application for the re-development of an existing dwelling known as

The Saltings, Coast Road, Norman’s Bay, Pevensey, East Sussex.

All flood risks have been considered but the only risk identified is tidal flooding from the sea due

immediately south of the site.

The modelling undertaken by Rother District Council, as part of its Strategic Flood Risk Assessment,

indicates there is no flooding at the site under breach conditions even for the 1 in 200 year event in

2115 which takes climate change into account. Very shallow flooding is predicted in the event of a

breach for the 1 in 1000 year event with climate change in 2115 and the depth of flood water is so

low that it would not affect the ground floor accommodation. This indicates the site is safe from

flooding for even the most severe of storms.

The re-development proposals retain the same footprint area but two options are being considered.

Option 1:-

The ground floor and first floor structure is retained but the existing spatial layout is re-arranged, the

building services are upgraded, the thermal performance is improved and the building envelope

upgraded. The first floor would be used for the main sleeping accommodation as currently

incorporated in the dwelling whilst a further bedroom is included in the ground floor as part of the

spatial re-arrangement. The existing ground floor is approximately 1.5 metres above the existing

ground levels so will be far more than 600 mm above the predicted flood water levels indicated from

the modelling results.

Option 2:-

Option 2 would result in a completely new dwelling being constructed on the existing base. The re-

arrangement of the spatial layout and upgrade of the building services, thermal performance and

building envelope would all be incorporated as for option 1 but further flood mitigation measures can

be included in the design. These could include the following:-

MONSON The Saltings, Coast Road, Norman’s Bay, Pevensey, East Sussex

Flood Risk Assessment

Issue A 2 24th April 2016 © Monson Engineering 2016

The windows in the first floor which face the sea could be constructed using safety glass to

prevent damage from any shingle flung against the dwelling due to wave and wind action.

Electricity meters and wiring could be installed on the first floor with drop downs to the

ground floor

The ground floor could incorporate tiling rather than carpets to reduce any impact of flooding

should water enter the property.

Waterproof plaster can be uses for the ground floor to again minimise any impact if water

does enter the property.

We would also advocate that the residents connect to the flood warning service so that they

can take the appropriate actions in the event of flood or severe flood warnings.

A further bedroom is proposed on the ground floor but all the modelling results indicate there is no

risk of flooding to this property due to its relative elevation compared to the marsh area to the north.

Therefore, whilst we have advocated the introduction of flood mitigation measures for the design

and construction of Option 2, there is deemed to be far less than a 1 in 1000 chance of the property

being affected by flood water even under a breach scenario in 2115 when the impacts of climate

change have been taken into account.

We would advocate that Option 2 is the preferred solution in terms of flood mitigation as it enables

more flood resilience measures to be introduced in the design and construction of the re-developed

dwelling.

Surface water drainage will be unaffected as the same roof area will be used.

We therefore recommend that no objection is raised to this application as the flood risk to the

property will not increase and will reduce due to the design of the re-development if Option 2 is

adopted.

MONSON The Saltings, Coast Road, Norman’s Bay, Pevensey, East Sussex

Flood Risk Assessment

Issue A 3 24th April 2016 © Monson Engineering 2016

1.0 INTRODUCTION

Monson have been requested to provide a Flood Risk Assessment for the re-development of an

existing dwelling known as The Saltings, Coast Road, Norman’s Bay, Pevensey, East Sussex.

The site is within flood zone 3 so a flood risk assessment is required to accompany any planning

application.

This report will conform to the National Planning Policy Framework and Technical Guidance

published in March 2012.

2.0 DEVELOPMENT DESCRIPTION AND LOCATION

2.1 Development type and location

The proposed development is the redevelopment of the existing dwelling at Norman’s Bay as

indicated on the location plan included in Appendix A.

2.2 Development classification

Household development is classified as “More Vulnerable” as defined in Table 2 of the Technical

Guidance to the National Planning Policy Framework. It is recognised that new development should

be directed to areas of lowest flood risk if possible. This site lies within flood zone 3 which is a high

risk area as indicated on the Environment Agency flood map for planning purposes included in

Appendix B. However, this site is already developed and the works proposed are to improve the

living accommodation within the existing property.

2.3 Sequential Test

The principle of the Sequential Test is to direct development towards areas of lowest flood risk. This

does not apply in this case as the proposed works are to an existing dwelling on this site.

MONSON The Saltings, Coast Road, Norman’s Bay, Pevensey, East Sussex

Flood Risk Assessment

Issue A 4 24th April 2016 © Monson Engineering 2016

2.4 Exception Test

The Exception Test needs to be applied as the site is within flood zone 3 but again as these works

are to an existing dwelling, the Exception Test does not apply.

3.0 DEFINITION OF THE FLOOD HAZARD

3.1 Flood sources

Flooding from the Sea

The site is situated on Coast Road, Norman’s Bay and is protected by the shingle bank running

directly in front of the property which provides a high level of protection. Nevertheless, the risk of

tidal flooding is a significant risk at this location.

Flooding from Rivers

There are a number of watercourses within the marsh areas to the north of the site but the property

is raised compared with the general marsh level beyond so there is no risk of fluvial flooding at this

location.

Flooding from Surface Water Run-Off and Overland Flow

The Environment Agency flood map for surface water, also included in Appendix B, indicates no

surface water flood risk. The area is extremely flat within the marsh area to the north of the property

and surface water is more likely to pond rather than collect at a single point which can lead to deep

surface water flooding. Again due to the elevation of the existing property, the risk of surface water

flooding is negligible.

Flooding from Groundwater

High water tables will occur in this general area due to the low elevation of the marshes and the flat

ground. However, groundwater flooding is normally associated with groundwater emerging from the

MONSON The Saltings, Coast Road, Norman’s Bay, Pevensey, East Sussex

Flood Risk Assessment

Issue A 5 24th April 2016 © Monson Engineering 2016

ground from porous underlying strata and collecting at a low point. This is not the case at this

location as the land is extremely flat.

Ponding of water in the marshes can occur but this would prove no risk to this site as the elevation

is above the general marsh level.

There is no risk of groundwater flooding at this location.

Flooding from Sewers.

There is a 150 mm foul sewer in Coast Road which drains to a pumping station almost opposite The

Saltings. The road and pumping station is below the existing dwelling so if the sewer was

overloaded or blocked, wastewater would flow towards the lower ground to the north of the site.

The sewer records indicate the road level is over 10 m ODN but we believe this must be a mistake

as the Coast Road is approximately 3 m ODN based on ordnance survey point levels along the road.

Flooding from Reservoirs, canals and other artificial sources.

The Environment Agency map for reservoirs shows no risk of flooding and there are no other artificial

sources in the vicinity which pose a risk to this site.

The principal risk to the proposed dwelling is from tidal flooding as indicated from the Environment

Agency’s flood map.

3.2 Surface water drainage

The site is at the back of the shingle bank and the downpipes from the roof discharge to soakaways

which will have excellent soakage characteristics.

The changes to the building will not extend the footprint of the building and therefore there will be

no increase in surface water discharge from the existing situation.

MONSON The Saltings, Coast Road, Norman’s Bay, Pevensey, East Sussex

Flood Risk Assessment

Issue A 6 24th April 2016 © Monson Engineering 2016

4.0 PROBABILITY

4.1 SFRA and other relevant data

The site is situated in flood zone 3 as indicated from the Environment Agency’s flood map (planning)

included in Appendix B. However, the Agency does also provide a tidal and fluvial flood risk map

which takes account of the sea defences and this shows the site to be in flood zone 2/3, which

means the risk lies between the 1 in 100 and 1 in 1000 year return storm event.

Rother District Council has undertaken a detailed Strategic Flood Risk Assessment covering their

whole area and this has included detailed modelling of the impacts of breaches to the sea defences.

One such breach modelled is at Norman’s Bay just east of the site and the results of the breach

analysis are included in Appendix C.

The modelling covered breaches for the existing scenario and also taking into account the impacts

of climate change in 100 years’ time. It is also assumed that no improvement to the sea defences

are undertaken despite the significant rise in sea levels over this period. The results show there is

no risk to the dwellings at this site even under the climate change situation for the 1 in 200 year

storm event. This is because of the raised elevation of the ground compared with the marsh level

behind the defences. It can be seen from the modelling results that the marsh area behind the flood

defences suffers deep flooding should breaches occur.

The modelling also considers the impacts of a breach in the 1 in 1000 year event and again this has

been considered for both the current situation and the climate change situation in 2115. This shows

only a very low level of flooding in the 2115 situation with a low flood hazard. This indicates the risk

of tidal flooding to the property is extremely small even should a breach occur in the flood defences.

The predicted flooding will only occur if there is a breach to the defences and this is unlikely due to

the depth and height of the defences in this location.

Spray from waves and the possible impact of shingle hitting the dwelling also need to be considered

as the dwelling is close to the top of the shingle bank.

MONSON The Saltings, Coast Road, Norman’s Bay, Pevensey, East Sussex

Flood Risk Assessment

Issue A 7 24th April 2016 © Monson Engineering 2016

5.0 CLIMATE CHANGE

The modelling undertaken for the Strategic Flood Risk Assessment has taken climate change into

account.

6.0 DETAILED DEVELOPMENT PROPOSALS

The plans for the proposed dwelling are included in Appendix D and there are two options:

Option 1:-

The ground floor and first floor structure is retained but the existing spatial layout is re-arranged, the

building services are upgraded, the thermal performance is improved and the building envelope

upgraded. The first floor would be used for the main sleeping accommodation as currently

incorporated in the dwelling whilst a further bedroom is included in the ground floor as part of the

spatial re-arrangement. The existing ground floor is approximately 1.5 metres above the existing

ground levels so will be far more than 600 mm above the predicted flood water levels indicated from

the modelling results.

Option 2:-

The superstructure of the existing dwelling is demolished but the base is retained. A new dwelling

will then be constructed on the existing base with the ground floor levels and first floor levels being

at the same height as the current dwelling. This will again enable the existing spatial layout to be

re-arranged and the building services, thermal performance and building envelope to be all

upgraded as for Option 1. One bedroom will also be included in the ground floor accommodation

as for Option 1 which again will be approximately 1.5 metres above existing ground level as in the

current dwelling.

7.0 SAFE ACCESS

Generally safe access can be achieved along Coast Road into the elevated urban areas of

Eastbourne to the west. However, we would advocate that the residents do not stay in the property

MONSON The Saltings, Coast Road, Norman’s Bay, Pevensey, East Sussex

Flood Risk Assessment

Issue A 8 24th April 2016 © Monson Engineering 2016

if a severe flood warning is issued as it would be safer to be away from the area in such

circumstances.

8.0 OFF SITE IMPACTS AND PROPOSED MITIGATION MEASURES

The proposed dwelling will retain the existing footprint area but two options are proposed:-

Option 1 would re-arrange the existing spatial layout and upgrade the building services, thermal

performance and building envelope. There would be no improvement in terms of flood protection

with this option.

Option 2 would result in a completely new dwelling being constructed on the existing base. The re-

arrangement of the spatial layout and upgrade of the building services, thermal performance and

building envelope would all be incorporated as for option 1 but further flood mitigation measures can

be included in the design. These could include the following:-

The windows in the first floor which face the sea could be constructed using safety glass to

prevent damage from any shingle flung against the dwelling due to wave and wind action.

Electricity meters and wiring could be installed on the first floor with drop downs to the

ground floor

The ground floor could incorporate tiling rather than carpets to reduce any impact of flooding

should water enter the property.

Waterproof plaster can be uses for the ground floor to again minimise any impact if water

does enter the property.

We would also advocate that the residents connect to the flood warning service so that they

can take the appropriate actions in the event of flood or severe flood warnings.

A further bedroom is proposed on the ground floor but all the modelling results indicate there is no

risk of flooding to this property due to its relative elevation compared to the marsh area to the north.

Therefore, whilst we have advocated the introduction of flood mitigation measures for the design

and construction of Option 2, there is deemed to be far less than a 1 in 1000 chance of the property

being affected by flood water even under a breach scenario I 2115 when the impacts of climate

change have been taken into account.

MONSON The Saltings, Coast Road, Norman’s Bay, Pevensey, East Sussex

Flood Risk Assessment

Issue A 9 24th April 2016 © Monson Engineering 2016

We would therefore propose that Option 2 is adopted as this does provide an opportunity to reduce

the flood risk through design whilst Option 1 will have a similar flood risk to the existing situation.

9.0 MANAGEMENT OF RESIDUAL RISKS

The flood mitigation proposals have been designed on the basis of the residual risk which is a breach

of the sea defences close to the site.

10.0 CONCLUSION

This report supports a planning application for the re-development of an existing dwelling known as

The Saltings, Coast Road, Norman’s Bay, Pevensey, East Sussex.

All flood risks have been considered but the only risk identified is tidal flooding from the sea due

immediately south of the site.

The modelling undertaken by Rother District Council, as part of its Strategic Flood Risk Assessment,

indicates there is no flooding at the site under breach conditions even for the 1 in 200 year event in

2115 which takes climate change into account. Very shallow flooding is predicted in the event of a

breach for the 1 in 1000 year event with climate change in 2115 and the depth of flood water is so

low that it would not affect the ground floor accommodation. This indicates the site is safe from

flooding for even the most severe of storms.

The re-development proposals retain the same footprint area but two options are being considered.

Option 1:-

The ground floor and first floor structure is retained but the existing spatial layout is re-arranged, the

building services are upgraded, the thermal performance is improved and the building envelope

upgraded. The first floor would be used for the main sleeping accommodation as currently

incorporated in the dwelling whilst a further bedroom is included in the ground floor as part of the

spatial re-arrangement. The existing ground floor is approximately 1.5 metres above the existing

MONSON The Saltings, Coast Road, Norman’s Bay, Pevensey, East Sussex

Flood Risk Assessment

Issue A 10 24th April 2016 © Monson Engineering 2016

ground levels so will be far more than 600 mm above the predicted flood water levels indicated from

the modelling results.

Option 2:-

Option 2 would result in a completely new dwelling being constructed on the existing base. The re-

arrangement of the spatial layout and upgrade of the building services, thermal performance and

building envelope would all be incorporated as for option 1 but further flood mitigation measures can

be included in the design. These could include the following:-

The windows in the first floor which face the sea could be constructed using safety glass to

prevent damage from any shingle flung against the dwelling due to wave and wind action.

Electricity meters and wiring could be installed on the first floor with drop downs to the

ground floor

The ground floor could incorporate tiling rather than carpets to reduce any impact of flooding

should water enter the property.

Waterproof plaster can be uses for the ground floor to again minimise any impact if water

does enter the property.

We would also advocate that the residents connect to the flood warning service so that they

can take the appropriate actions in the event of flood or severe flood warnings.

A further bedroom is proposed on the ground floor but all the modelling results indicate there is no

risk of flooding to this property due to its relative elevation compared to the marsh area to the north.

Therefore, whilst we have advocated the introduction of flood mitigation measures for the design

and construction of Option 2, there is deemed to be far less than a 1 in 1000 chance of the property

being affected by flood water even under a breach scenario in 2115 when the impacts of climate

change have been taken into account.

We would advocate that Option 2 is the preferred solution in terms of flood mitigation as it enables

more flood resilience measures to be introduced in the design and construction of the re-developed

dwelling.

Surface water drainage will be unaffected as the same roof area will be used.

MONSON The Saltings, Coast Road, Norman’s Bay, Pevensey, East Sussex

Flood Risk Assessment

Issue A 11 24th April 2016 © Monson Engineering 2016

We therefore recommend that no objection is raised to this application as the flood risk to the

property will not increase and will reduce due to the design of the re-development if Option 2 is

adopted.

MONSON The Saltings, Coast Road, Norman’s Bay, Pevensey, East Sussex

Flood Risk Assessment

Issue A A 24th April 2016 © Monson Engineering 2016

APPENDIX A - SITE LOCATION

MONSON The Saltings, Coast Road, Norman’s Bay, Pevensey, East Sussex

Flood Risk Assessment

Issue A B 24th April 2016 © Monson Engineering 2016

APPENDIX B - ENVIRONMENT AGENCY MAPS;

FLOOD MAP FOR SEA AND RIVER (PLANNING)

FLOOD MAP FOR SEA AND RIVER

FLOOD MAP FOR SURFACE WATER

FLOOD MAP FOR RESERVOIRS

Environment Agency - What's in your backyard?

http://maps.environment-agency.gov.uk/...floodmap&layer=default&ep=map&layerGroups=default&scale=11&x=567665&y=105391#x=567930&y=105391&lg=1,2,10,&scale=11[24/05/2016 09:39:39]

Other maps Data search Text only versionMap legend

Click on the map to see whatFlood Zone (NationalPlanning Policy Guidancedefinitions) the proposeddevelopment is in.

Flood Map for Planning(Rivers and Sea)

Flood Zone 3

Flood Zone 2

Flood defences(Not all may be shown*)

Areas benefiting fromflood defences(Not all may be shown*)

Main River Line

Main River Line

Other nationalenvironmentalorganisations

Natural ResourcesWales Area ofresponsibility

Scottish EnvironmentProtection Agency Areaof responsibility

Enter a postcode or place name:

Other topics for this area...

Flood Map for Planning (Rivers and Sea)

Flood Map for Planning (Rivers andSea)

X: 567,930;Y: 105,391 at scale 1:10,000

Customers in Wales - From 1 April 2013 Natural Resources Wales (NRW) has taken over the responsibilities of the Environment Agency in Wales.© Environment Agency copyright and database rights 2016. © Ordnance Survey Crown copyright. All rights reserved. Environment Agency, 100026380.

Contains Royal Mail data © Royal Mail copyright and database right 2016.This service is designed to inform members of the public, in line with our terms and conditions. For business or commercial use, please contact us.

More about flooding:

Understanding the Flood Map for Planning (Rivers and Sea)

A more detailed explanation to help you understand the flood map shown above.

Current flood warnings

We provide flood warnings online 24 hours a day. Find out the current flood warning status in your local area.

* Legend Information: Flood defences and the areas benefiting from them are gradually being added throughupdates. Please contact your local environment agency office for further details.

Environment Agency - Risk of Flooding from Rivers and Sea

http://watermaps.environment-agency.gov.uk/...spx?topic=floodmap&scale=11&ep=map&layerGroups=default&lang=_e&y=105391&x=567929#x=567929&y=105391&scale=11[24/05/2016 09:40:52]

Data searchMap legend

Risk of Flooding fromRivers and Sea

High

Medium

Low

Very Low

Other nationalenvironmentalorganisations

Natural Resources WalesArea of responsibility

Scottish EnvironmentProtection Agency Area ofresponsibility

Author: The Environment Agency | enquiries@environment-agency.gov.ukLast updated: 24 May 2016

Enter a postcode or place name:

Other topics for this area...

Risk of Flooding from Rivers and Sea

View other Interactive Maps

Risk of Flooding from Rivers and SeaRiver flooding happens when a river cannot cope with the amount of water draining into it from the surrounding land. Sea floodinghappens when there are high tides and stormy conditions.

The shading on the map shows the risk of flooding from rivers and the sea in this particular area.

Click on the map for a more detailed explanation.

Map of X: 567,929; Y: 105,391 at scale 1:10,000

Customers in Wales - From 1 April 2013 Natural Resources Wales (NRW) will take over the responsibilities of the Environment Agency in Wales. © Environment Agency copyright and database rights 2016. © Ordnance Survey Crown copyright. All rights reserved. Environment Agency, 100026380.

Contains Royal Mail data © Royal Mail copyright and database right 2016. This service is designed to inform members of the public, in line with our terms and conditions. For business or commercial use, please contact us.

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200 m1000 ft

Environment Agency - Risk of Flooding from Surface Water

http://watermaps.environment-agency.gov.uk/wiyby/wiyby.aspx?lang=_e&topic=ufmfsw&layer=default&scale=11&x=567929&y=105391#x=567929&y=105391&scale=11[24/05/2016 09:41:28]

Data searchMap legend

Risk of Flooding fromSurface Water

High

Medium

Low

Very Low

Other nationalenvironmentalorganisations

Natural Resources WalesArea of responsibility

Scottish EnvironmentProtection Agency Area ofresponsibility

Author: The Environment Agency | enquiries@environment-agency.gov.ukLast updated: 24 May 2016

Enter a postcode or place name:

Other topics for this area...

Risk of Flooding from Surface Water

View other Interactive Maps

Risk of Flooding from Surface WaterSurface water flooding happens when rainwater does not drain away through the normal drainage systems or soak into theground, but lies on or flows over the ground instead.

The shading on the map shows the risk of flooding from surface water in this particular area.

Click on the map for a more detailed explanation.

Map of X: 567,929; Y: 105,391 at scale 1:10,000

Customers in Wales - From 1 April 2013 Natural Resources Wales (NRW) will take over the responsibilities of the Environment Agency in Wales. © Environment Agency copyright and database rights 2016. © Ordnance Survey Crown copyright. All rights reserved. Environment Agency, 100026380.

Contains Royal Mail data © Royal Mail copyright and database right 2016. This service is designed to inform members of the public, in line with our terms and conditions. For business or commercial use, please contact us.

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200 m1000 ft

569245, 106142

Environment Agency - Risk of Flooding from Reservoirs

http://watermaps.environment-agency.gov.uk/wiyby/wiyby.aspx?lang=_e&topic=reservoir&layer=default&scale=11&x=567929&y=105391#x=567929&y=105391&scale=11[24/05/2016 09:41:06]

Data searchMap legend

Risk of Flooding fromReservoirs

Maximum extent offlooding

Other nationalenvironmentalorganisations

Natural Resources WalesArea of responsibility

Scottish EnvironmentProtection Agency Area ofresponsibility

Author: The Environment Agency | enquiries@environment-agency.gov.ukLast updated: 24 May 2016

Enter a postcode or place name:

Other topics for this area...

Risk of Flooding from Reservoirs

View other Interactive Maps

Risk of Flooding from ReservoirsReservoir flooding is extremely unlikely to happen.

The shading on the map shows the area that could be flooded if a large reservoir were to fail and release the water it holds. Alarge reservoir is one that holds over 25,000 cubic metres of water, equivalent to approximately 10 Olympic sized swimming pools.Since this is a worst case scenario, it’s unlikely that any actual flood would be this large.

Click on the shading to see details of reservoirs that could cause flooding in this area.

Map of X: 567,929; Y: 105,391 at scale 1:10,000

Customers in Wales - From 1 April 2013 Natural Resources Wales (NRW) will take over the responsibilities of the Environment Agency in Wales. © Environment Agency copyright and database rights 2016. © Ordnance Survey Crown copyright. All rights reserved. Environment Agency, 100026380.

Contains Royal Mail data © Royal Mail copyright and database right 2016. This service is designed to inform members of the public, in line with our terms and conditions. For business or commercial use, please contact us.

Follow us: YouTube Twitter Flickr Facebook

Privacy policy | Terms and conditions | Contact us | Cymraeg © Environment Agency 2016

200 m1000 ft

MONSON The Saltings, Coast Road, Norman’s Bay, Pevensey, East Sussex

Flood Risk Assessment

Issue A C 24th April 2016 © Monson Engineering 2016

APPENDIX C – MODELLING OUTPUT FROM ROTHER DISTRICT

COUNCIL’S STRATEGIC FLOOD RISK ASSESSMENT

MONSON The Saltings, Coast Road, Norman’s Bay, Pevensey, East Sussex

Flood Risk Assessment

Issue A D 24th April 2016 © Monson Engineering 2016

APPENDIX D – DEVELOPMENT PROPOSALS