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Background to the PFRA European Overview - UC9810.5b

The individual Member State Reports reflect the situation as reported

by the Member States to the European Commission in 2012

The situation in the MSs may have altered since then

Assessment of data and information reported by Member States on their

Preliminary Flood Risk Assessments and identification of Areas of

Potentially Significant Flood Risk under the Floods Directive

Member State Report: [UK] - [United Kingdom]

The main outcomes of the assessment were:

1. There are significant differences in how the requirements of the Floods Directive have been

implemented in the UK. In England and Wales Article 4 has been applied in terms of flooding

from ordinary (minor) watercourses and all other sources of local flooding, groundwater, and

pluvial, and Article 13.1.b to the main rivers and large raised reservoirs and sea water. In Scotland

Article 4 has been applied to all relevant types of flood, and in Northern Ireland, Article 4 has

been applied to fluvial and pluvial flooding. Finally in Gibraltar, Article 4 has been applied

specifically to sea water floods. There are also significant differences in the methodological

approaches between the 4 regions of the UK.

2. Article 4 has been applied in Scotland, Northern Ireland and Gibraltar for all types of flooding

considered as relevant. In England and Wales, this Article has only been applied by Lead Local

Flood Authorities (LLFA) who are responsible for pluvial and groundwater flooding, and from

minor watercourses which include ditches and streams not included as main rivers.

3. Article 13.1(a) has not been applied to any specific area or specific type of flood for any of the

RBDs in the UK.

4. Article 13.1(b) has only been applied to the UoMs in England and Wales and is applied to

floods from sea water, main rivers and large raised reservoirs. The only information reported to

WISE on methodologies was the overall approach, with the same text as reported for Article 4.

5. Only Scotland reported details (type and consequence) of significant historical flood events to

WISE. England (361) and Wales (113) (E&W) provided summaries of flood events instead of the

specific details requested. Northern Ireland also reported summaries of 27 flood events rather than

in the detail requested. In Gibraltar, a summary of 1 flood event was reported to WISE.

6. In Scotland, the location of future floods is primarily predicted and information on historic

floods is used to validate the predictions. In England and Wales, LLFAs used computer models to

generate information on future floods. In Northern Ireland, the future flood risk is assessed using a

GIS based Source – Pathway Receptor model that combines the output from predictive flood

models with a digital terrain model and a host of readily available receptor datasets. In Gibraltar,

no modelling for future flooding was undertaken and the assessment was based on largely

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anecdotal evidence of past flooding. Only flooding from rainfall and storm surges from the sea

were considered to be significant for future risk assessments.

7. Adverse consequences were defined and considered, with regional differences in approach and

methodology.

8. All regions have given consideration to the impact of climate change on future flood risk.

Scotland, England, Wales and Northern Ireland have also considered the effect of building and

planning.

Question 0: Contextual information regarding the Member State.

There are 3 main regions in the main part of the UK: Northern Ireland (3 UoMs); Scotland

(1 main UoM (UK01) plus part of the UoM shared with England (UK02); and, England

and Wales (10 UoMs, one shared with Scotland). In addition Gibraltar (UKGI17) reported

a PFRA and APSFR. Information from 17 XML (two for UK02) files was included in the

WISE aggregation reports and was therefore used in the assessment. In addition, a number

of relevant documents were downloaded from the relevant national web sites to obtain

more detailed and specific information where necessary. The documents downloaded and

examined were:

Title Source

The National Flood Risk Assessment,

December 2011(of Scotland),

downloaded from the Scottish Environment

Protection Agency web site:

http://www.sepa.org.uk/flooding.aspx

Flood Risk Management (Scotland) Act 2009

Appraisal Method for Flood Risk Management

Strategies (not dated)

downloaded from the Scottish Environment

Protection Agency web site

http://www.sepa.org.uk/flooding.aspx

Flood Risk Management (Scotland) Act 2009

(FRM Act) National Flood Risk Assessment

Methodology, (not dated)

downloaded from the Scottish Environment

Protection Agency web site.

http://www.sepa.org.uk/flooding.aspx

Preliminary Flood Risk Assessment (PFRA),

Annexes to the final guidance Report –

GEHO1210BTHF-E-E, 2 March 2011.

downloaded from Environment Agency

(England) web site.

http://a0768b4a8a31e106d8b0-

50dc802554eb38a24458b98ff72d550b.r19.cf3.r

ackcdn.com/geho1210bthf-e-e.pdf

Flood Risk Management Plans: Guidance for

Risk Management Authorities in England and

Wales, A Living Draft, August 2013

downloaded from Environment Agency

(England) web site.

http://a0768b4a8a31e106d8b0-

50dc802554eb38a24458b98ff72d550b.r19.cf3.r

ackcdn.com/LIT_8649_4e4b09.pdf

Selecting and reviewing Flood Risk Areas for

local sources of flooding, Guidance to Lead

Local Flood Authorities, Flood Risk

Regulations 2009, (2010)

downloadable from www.defra.gov.uk or

www.cymru.gov.uk

Flooding in England: A National Assessment of

Flood Risk (2009)

downloaded from Environment Agency

(England) web site. http://www.environment-

agency.gov.uk/research/library/publications/10

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8660.aspx

Preliminary Flood Risk Assessment and

Methodology for the Identification of

Significant Flood risk Areas December 2011,

Rivers Agency of Northern Ireland,

downloaded from web

http://www.dardni.gov.uk/final-pfra-report.pdf

Government of Gibraltar, Preliminary Flood

Risk Assessment, Final Report, January 2011

Downloaded from the web.

https://www.gibraltar.gov.gi/new/sites/default/f

iles/docs/Preliminary%20Flood%20Risk%20As

sessment%20Report.pdf

Flooding is a devolved responsibility for Wales, Scotland and Northern Ireland and so

there are significant differences in how the requirements of the Floods Directive have been

implemented in the UK. In England and Wales Article 4 has been applied in terms of

flooding from ordinary (minor) watercourses and all other sources of local flooding,

groundwater, and pluvial, and Article 13.1.b to the main rivers and large raised reservoirs

and sea water. In Scotland Article 4 has been applied to all relevant types of flood, and in

Northern Ireland, Article 4 has been applied to fluvial and pluvial flooding. Finally in

Gibraltar, Article 4 has been applied specifically to sea water floods. There are also

significant differences in the methodological approaches between the 4 regions of the UK.

Table 1 The application of Articles, 4, 13.1.a and 13.1.b in the Units of Management of

the United Kingdom Source: WISE Flood aggregation report “FD 1.1 Specific Areas to which each Article has been applied”

UoM Article 4 Article

13.1.a

Article

13.1.b

UK01 1 0 0

UK02_England 1 0 1

UK02_Scotland 1 0 0

UK03 1 0 1

UK04 1 0 1

UK05 1 0 1

UK06 1 0 1

UK07 1 0 1

UK08 1 0 1

UK09 1 0 1

UK10 1 0 1

UK11 1 0 1

UK12 1 0 1

UKGBNIIENB 1 0 0

UKGBNIIENW 1 0 0

UKGBNINE 1 0 0

UKGI17 1 0 0 Note: if the Articles have not been applied to or reported for any specific area, it is assumed that they have been applied to the

entire UoM. In which case the values in the table above will equate to 1. Values of zero for any Article or UoM indicate that that

the Article has not been applied to that UoM.

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Table 2 Specific types of floods to which Article 4, 13.1.a and 13.1.b have been applied

Source: WISE Flood aggregation report: “FD 1.2 Types of flood to which each Article has been applied”

Article UoM Source * Mechanism * Characteristic * All types

**

Article 4 UK02_Englan

d, UK03,

UK04, UK05,

UK06, UK07,

UK08, UK09,

UK10, UK11,

UK12

"Ordinary

(minor)

watercourses

and all other

sources of local

flooding",

Groundwater,

Pluvial

Article 4 UKGBNIIEN

B,

UKGBNIIEN

W,

UKGBNINE

Fluvial, Pluvial

Article 4 UKGI17 Sea water Defence

exceedance

"Natural Flood"

Article 4 UK01,

UK02_Scotlan

d

yes

Article

13.1.b

UK02_Englan

d, UK03,

UK04, UK05,

UK06, UK07,

UK08, UK09,

UK10, UK11,

UK12

"Main Rivers

and large raised

reservoirs", Sea

water

* Source, mechanism and characteristics in quotation marks is source, mechanism and characteristics specified by member state

** No specific flood types were reported and it is assumed that Article 4 is applied to all flood types

Question 1: Are all the types of flood that might be reasonably expected in the Member State

included in the assessment of the risk of flooding under Article 4, Article 13.1(a) or Article

13.1(b)?

Source Included Not included but

Yes/No might be expected

Fluvial Yes

Pluvial Yes

Groundwater Yes

Sea water Yes

Artificial

water-bearing

infrastructure Yes

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Other (provide

details in the

summary

below) No Yes

Summary assessment

There are 4 distinct regions in the UK relevant to this assessment: Scotland (UK01 and

part of UK02); England and Wales (UK03 to UK12); Northern Ireland (one report

covering the 3 UoMs); and Gibraltar. There are some differences in the reported

information.

In Scotland the National Flood Risk Assessment concentrated on rivers, coastal flooding

and heavy rainfall with some (though limited) consideration of the influence of

groundwater. No explicit mention is made of flooding from natural lakes (this is the other

options ticked above) or artificial water bearing infrastructure including reservoirs or

flooding from sewerage systems. Scotland has subsequently indicated that natural lakes

were part of the fluvial network for which flood extents were developed. Additionally,

flood risk information on a sub-set of Scotland’s sewerage systems was developed after the

NFRA but has been embedded into Scotland’s surface water flooding maps. It is not

considered a nationally significant source of flooding. Finally, groundwater was included

but is not considered a primary source of flooding; rather it is a contributing factor to other

types of flooding. Therefore, there is limited data on groundwater flooding that would

support further investigation.

In England and Wales, the Environment Agency has applied Article 13.1.b and is adapting

the current hazard and risk maps to the requirement of the Floods Directive (WISE

aggregation report). They are responsible for the main rivers, the sea and large raised

reservoirs. England and Wales have subsequently indicated that PFRAs were not produced

for river and coastal flooding as flood hazard and flood risk maps have been produced for

the whole of England and Wales instead of identifying APSFRs. Future work will produce

Flood Risk Management Plans for the whole of England and Wales. Lead Local Flood

Authorities have applied Article 4 to surface runoff, groundwater and ordinary watercourse

and any interactions these have with drainage systems and other sources of flooding

including sewers (except in terms of blockages or failures) and also excluding burst

(potable) water mains. Flooding from canals that are not main rivers should also be

included in the PFRA. The EA considers snowmelt as precipitation that would lead to

surface run-off and tsunamis as a form of sea flooding: it is not clear how the risk from

these latter two sources would have been assessed. No explicit mention is made of

flooding from natural lakes (this is the other options ticked above).

In Northern Ireland the main flooding sources considered were rivers, the sea, surface

water run-off and impounded water bodies (dams and reservoirs) though the latter source

was not conclusively assessed because of the lack of readily available information to make

this assessment: this shortfall will be dealt with in the future when new regulations will

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enable the collection for the relevant data on reservoirs and dams. Groundwater flooding

was excluded because it was considered insignificant in Northern Ireland compared to the

other sources. There is also no explicit mention of natural lakes as a source of flooding.

In Gibraltar, 5 sources of flooding were considered: rivers, sea, surface run-off,

groundwater and infrastructure (flood defence) failure. There are no watercourses (rivers)

in Gibraltar and the risk from groundwater was considered as minimal (because of the

hydrogeology) and these sources were considered as representing no risk.

Table 3 Time period covered by different types of historic flood events

Source: WISE Flood aggregation report: “FD 2.0 Time period covered by historic flood events”

Source Total flood

events

Range of

years

2000

onwards

1950 to

1999

1900 to

1949

1800s Before

1800

Fluvial 92 1900-2009 19 27 46 0 0

Pluvial 15 1907-2010 5 2 8 0 0

Sea water 16 1949-2005 1 14 1 0 0

Artificial water-bearing

infrastructure

10 1990-2009 2 8 0 0 0

Other: Peat

Slide/Debris Flow/Bog

Burst

2 1979-2004 1 1 0 0 0

No data 13 1914-2008 5 7 1 0 0

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Table 4 Types of historical significant flood events and types of reported consequences

Source: WISE Flood aggregation report: “FD 2.1 Types of historical significant flood events”

Member

State

Article

Source

Mechanism

Characteristics Number of

Historical

floods

Number of

flood events with no

data

Number with reported consequences

Human

Health

Environment Cultural

Heritage

Economic

Activity

UK Article 4 no data 13 0 14 13 13 13

UK Article 4 "Peat Slide/Debris

Flow/Bog Burst"

2 0 2 2 2 2

UK Article 4 Artificial water-bearing

infrastructure

10 0 10 10 10 12

UK Article 4 Fluvial 92 0 95 92 92 124

UK Article 4 Pluvial 15 0 16 15 15 19

UK Article 4 Sea water 16 0 16 16 16 20

Table 5 Types of potential future significant flood events and types of consequences

Source: WISE Flood aggregation report: “FD 3.1 Types of potential future significant flood events”

Member

State

Article

Source

Mechanism

Characteristics Number of

Potential

Future floods

Number

of flood events

with no data

Number with reported consequences

Human

Health

Environment Cultural

Heritage

Economic

Activity

UK Article 4 "Main rivers" Natural exceedance Medium onset

flood

24 0 24 24 24 24

UK Article 4 "Ordinary (minor)

watercourses"

Natural exceedance Flash flood 2 0 2 2 2 2

UK Article 4 "Ordinary (minor)

watercourses"

Natural exceedance Medium onset

flood

11 0 11 11 11 11

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UK Article 4 Artificial water-

bearing infrastructure

Defence or

infrastructural failure

Flash flood 3 0 3 3 3 3

UK Article 4 Groundwater Natural exceedance Medium onset

flood

14 0 14 14 14 14

UK Article 4 Pluvial Defence exceedance Medium onset

flood

1 0 1 1 1 1

UK Article 4 Pluvial Natural exceedance 2 0 2 2 2 2

UK Article 4 Pluvial Natural exceedance Flash flood 1 0 1 1 1 1

UK Article 4 Pluvial Natural exceedance Medium onset

flood

134 0 134 134 134 134

UK Article 4 Sea water Defence exceedance "Natural Flood" 1 0 1 1 1 1

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Question 2a: What aspects required by Article 4 were not considered in the application of

Article 4?

Has Article 4 been applied?

Yes, information has been reported on this aspect

Summary assessment

This Article has been applied in Scotland, Northern Ireland and Gibraltar for all types of

flooding considered as relevant. In England and Wales, this Article has only been applied

by Lead Local Flood Authorities (LLFA) who are responsible for pluvial and groundwater

flooding, and from minor watercourses which include ditches and streams not included as

main rivers (which are the responsibility of the Environment Agency of England and

Wales who are applying Article 13.1.b for this type and some other types of flood).

Based on the information reported to WISE, in Scotland all the expected aspects have been

included in the PFRA.

In England and Wales the Environment Agency provided the LLFAs guidance on what

was required in a PFRA. Based on the guidance and the WISE report (and not an example

of a PFRA produced by a LLFA) it seems that most aspects would have been included.

However, there may be some limitations in the assessment of the risk from groundwater

flooding as the dataset used (Areas Susceptible to Groundwater Flooding) is quoted not to

be interpreted as identifying areas where groundwater is actually likely to flow or pond:

rather it should be used to identify where further studies would be useful. England and

Wales has subsequently indicated that further assessment of groundwater flooding is being

considered as a result of flooding events that occurred in 2014. In terms of surface water

flooding there was also no readily available or derivable information about the

effectiveness of existing man made infrastructure (drainage). LLFAs are also response for

assessing the hazard and risk from minor water courses. Some of these may have been

covered by existing datasets but there may also have been gaps in the aspects such their

geomorphological characteristics that were not included.

For the PFRA in Northern Ireland most aspects have been considered. There was an initial

consideration of the geomorphological characteristics of watercourses. Northern Ireland

has subsequently indicated that it was not possible to develop a practicable broad-scale

approach that would be sufficiently robust to support a meaningful assessment of the

potential for geomorphological activity to change the future flood risk from the many

hundreds of rivers under consideration. The effectiveness of flood defences was also

ignored in the indicative (strategic) flood models used to assess the potential adverse

consequences of future floods because of the uncertainty associated with the actual levels

of protection offered by the existing defences (river walls, flood banks, culverts etc.). This

approach was adopted to ensure that communities located behind the existing major flood

defence systems were identified as areas of potential significant flood risk and thereby

create the opportunity to develop detailed predictive flood models and produce hazard and

risk maps that illustrate the estimated level of protection provided to the areas by the

defences.

The PFRA for Gibraltar also covers all aspects that are relevant to the characteristics of

water bodies in Gibraltar.

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Question 2b: What aspects required by Article 4 were not considered when producing an

assessment of the risk of flooding under Article 13.1(a)?

Has Article 13.1(a) been applied?

No, it is explicitly stated that this Article has not been applied

Summary assessment

This Article has not been applied to any specific area or specific type of flood for any of

the RBDs in the UK.

Question 3: What aspects required by Article 4 were not considered when producing Flood

Hazard Maps and flood risk maps, and Flood Risk Management Plans under Article 13.1(b)?

Has Article 13.1(b) been applied?

Yes, information has been reported on this aspect

Summary assessment

In the UK, this Article has only been applied to the UoMs in England and Wales (part of

UK02 and UK03 to UK12), and is applied to floods from sea water, main rivers and large

raised reservoirs. Large reservoirs are defined by a size criterion of 25,000 m3 capacity

though this is to be decreased to 10,000 m3 capacity on implementation of new legislation.

The Environment Agency of England and Wales will produce flood hazard and risk maps

and flood risk management plans for flood risk from main rivers, large raised reservoirs

and the sea by adapting the existing maps and plans to meet the requirements of the Floods

Directive. The only information reported to WISE on Article 13.1.b methodologies was on

the overall approach: this was the same text as reported for Article 4 and only describes the

respective role of the EA and Lead Local Flood Authorities. A search of the Environment

Agency of England and Wales’ web site did not locate any detailed methodological reports

on the basis of existing flood hazard and flood risk maps. The statement that existing maps

will be adapted to meet the requirements of the Floods Directive implies that the current

maps do not cover all aspects outlined in Article 4. In addition no specific information was

found on how the risk from large raised reservoirs would be assessed.

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Question 4: What are the types of floods considered/not considered within the auspices of the

Floods Directive?

Summary assessment

Considering the UK as a whole, fluvial, pluvial, groundwater, sea water and floods from

artificial water bearing infrastructure have been considered but there are significant

regional differences.

Peat slide/debris flow/ bog burst floods were reported (in WISE) for Scotland (UK01) as

historic but not potential future flood event. Scotland has subsequently indicated that the

lack of available, detailed and reliable information on these types of flood prevented them

from being included in the future flood assessment. Historic flooding in Scotland has also

resulted from snow melt and ice blockages but again these were not included in the future

flood assessment due to a lack of information and because they are infrequent and not

considered significant. In Scotland the National Flood Risk Assessment (2011)

concentrated on rivers, coastal waters and pluvial flooding with a “further consideration of

the influence of groundwater”. However in the Scotland report (Appraisal method for

Flood Risk Management Strategies First edition) it is stated that “Groundwater flooding

will not be considered within the appraisal process. Accurate data relating to groundwater

risk in Scotland is not currently available, and there is uncertainty related to the potential

for groundwater to cause flooding. It is understood that groundwater issues can exacerbate

flooding from other sources however, the levels of flooding attributed to groundwater are

uncertain.”

Raised reservoirs over 10,000 m3 capacity (artificial water bearing structures) are included

in England Wales but not in Northern Ireland (because of a lack of information even

though they are considered as being potentially significant) or in Scotland (no reason

found). Scotland has subsequently indicated that this was due to a lack of available and

reliable information prior to submission. It also noted that the Reservoirs (Scotland) Act

2011 includes a responsibility for SEPA to assign a risk designation to all reservoirs over

10,000 m3 capacity. This will be based on the potential adverse consequences of an

uncontrolled release of water and the probability of such a release. The outputs from these

assessments will be considered for inclusion in future reporting cycles.

Canals are also considered in England and Wales. In England and Wales a differentiation

is made between main rivers and ordinary water courses (e.g. stream, ditches and sluice) in

terms of fluvial flooding for which, respectively, the Environment Agency of England and

Wales and the Local Lead Flood Authorities (municipal authorities) are responsible (WISE

report). Scotland has subsequently indicated that canals were not included in the

assessment for Scotland as flood risk from canals is not considered significant and little

information was available, Flooding from sewers does not have to be considered in

England and Wales unless wholly or partly caused by rainwater entering or otherwise

affecting the system (WISE).

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Groundwater flooding is also considered to be insignificant in Northern Ireland (PFRA

report) compared to other sources, as confirmed by a desktop review of hydrogeology and

flooding history that demonstrated no areas at significant risk from groundwater flooding.

In Gibraltar (UK17) (PFRA document) only two sources of potential flooding (pluvial and

sea water) were considered to represent a risk (i.e. significant): there are no surface

watercourses and the hydrological characteristics of the groundwater aquifers led to the

conclusion that they represented no risk. A residual risk was considered to arise from sea

flood defence failure during extreme tidal events.

Question 5: What were the criteria used to define the historical significant floods and what

were the reasons for not including some types of flood that occurred in the past?

Summary assessment

Only Scotland reported details (type and consequence) of significant historical flood

events to WISE. Historic flood events were collated from a number of sources including

SEPA data and newspaper records. 15,000 individual flood events were found covering all

of Scotland. An impact score was assigned to each event ranging from 0 (very low impact)

to 4 a very high impact. Impact was based on the effects on receptors including Human

Health, Economic Activity, Environment and Cultural Heritage. Threshold criteria (not

reported or found) were associated with the impacts on each receptor, the exceedance of

which indicated significance. Any event which has a very high impact (4) was deemed to

be significant.

England (361) and Wales (113) (E&W) provided summaries of flood events rather than

details, as permitted in this reporting cycle. Defra has subsequently indicated that this was

because information on past flood events was not readily derivable. The reported

information for E&W is for the PFRAs undertaken by the Lead Local Flood Authorities

(e.g. county council and unitary administrative authorities) which have responsibility for

flooding from defined sources such as pluvial and groundwater. The Environment Agency

(EA) of E&W has responsibly for other sources of flooding such from main rivers and sea

water and they have applied Article 13.1.b and hence are not producing PFRAs but are

going straight to the development/revision of existing Flood Hazard (FH) and Flood Risk

(FR) Maps. The Environment Agency (EA) provided guidance to the LLFAs on the

production of PFRA which listed a number of sources of historic flood information. It is

not clear how (or if) the EA used the historic information in the development of the FH

and FR maps as their method seems to be solely based on modelling. The relevant

information was sought for in a number of EA publications downloaded from their web

site including “National Assessment of Flood Risk”. In terms of the LLFAs, the factors

used to determine the significance of any harmful consequences of historic flood events

included those that were significant on a national scale; how memorable the event was;

scale of the flooding and consequences and the level of response; severity of impacts; and

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on whether the quality of the information was sufficient to determine if there were

significant harmful consequences.

Northern Ireland also reported summaries of 27 flood events rather than in detail, as

permitted within this reporting cycle. In Northern Ireland a library and media review of

flood events was undertaken to establish the extent of major floods events dating back to

early 1900’s. Since 1980 floods have been recorded by aerial photography. The Flood risk

associated with post 1980 flood events has been assessed using a GIS application which

calculated key Flood Risk Indicators associated with their adverse consequences to Human

Health, economic activity, Environment and cultural heritage. No information was found

on what criteria equated to a historic event being significant in Northern Ireland.

In Gibraltar, information on past floods was found from a wide range of sources including

Government departments, museums and utility companies. A summary of 1 flood event

was reported to WISE. There was no information on what equated to a historic significant

floods though groundwater floods were not considered in the PFRA because there were no

recorded events from this source. No information was found from the other parts of the

UK on the basis of exclusion of specific flood types from the consideration of historic

flood events.

Question 6: What methods and criteria were used to identify potentially significant future

floods and what were the reasons for not including some types of potential future floods?

Summary assessment

In Scotland the location of future floods is primarily predicted. Information on historic

floods is used to validate the predictions. The 1 in 200 year (annual exceedance

probability of 0.5%) indicative river and coastal flood extents were used and these were

integrated with national (Scottish) pluvial and groundwater datasets. A systematic 1km2

grid approach was used in assessing flood hazard to defined receptors from fluvial, coastal

and pluvial flood sources. A groundwater factor was also applied for areas which were

classified as having a high or very high susceptibility to flooding. In general however the

focus of the National Flood Risk Assessment (NFRA) was on fluvial, pluvial and coastal

flooding rather than that from groundwater. The significance of the records of historic

flood events was assessed using a scoring method incorporating the impact, source and

reliability of the event. This data was then used to validate the NFRA grid output ensuring

that significant historic events were used in the determination of Potentially Vulnerable

Areas. Because of some uncertainty in the methods for assessing flood risks, a manual

review was undertaken to take account of any uncertainties within the grid outputs.

In terms of the sources of flooding (pluvial, groundwater and ordinary watercourse) for

which the LLFAs are responsible in England and Wales, computer models were used to

generate information on future floods. In terms of surface run-off the derived national

datasets included areas susceptible to surface water flooding and the flood map for surface

14 of 25

water. The assessment was based on flooding to a depth of 0.3 metres by a rainfall event

with a chance of 1 in 200 of occurring in any given year (equivalent to 'in the order of' 1 in

100 chance of flooding). These datasets were supplemented by locally agreed surface

water information which best represented local conditions. For groundwater a national 1

km2 grid datasets was used where no local information was available. In terms of ordinary

water course there were no datasets that dealt solely with this source and so national

surface run-off datasets were used when possible supplemented by any local information.

No specific information relating to the Environment Agency’s methods for assessing the

risk of flooding from coastal waters, main rivers and from raised reservoirs was found in

spite of extensive search on the relevant web sites.

In Northern Ireland the future flood risk is assessed using a GIS based Source – Pathway

Receptor model that combines the output from predictive flood models with a digital

terrain model and a host of readily available receptor datasets. The assessment of the

potential adverse consequences of flooding is based on three different probability events

(low, medium and high) for each of the flood sources. By producing flood outlines with

different return periods it was possible to ‘annualise’ Flood Risk Indicator values to

produce estimates of the adverse effects that best represent the true long term annual

average. The AEP of the events used in the assessment for each source is fluvial: 10%, 1%

and 0.1%, coastal; 10%, 0.5% and 0.1% and pluvial 10%, 0.5% and 0.1%. No information

was reported on the methods for groundwater and artificial water bearing infrastructure.

In Gibraltar no modelling for future flooding was undertaken and the assessment was

based on largely anecdotal evidence of past flooding. Only flooding from rainfall and

storm surges from the sea were considered to be significant for future risk assessments.

Question 7: What types of flood were considered but not assessed as being significant, and what

were the reasons given?

Summary assessment

In Scotland the significance of historic floods was assessed by assigning an impact score

to each event ranging from 0 - 4, where 0 indicates a Very Low impact event and 4

indicates a Very High Impact event. This allowed areas historically prone to flooding to be

highlighted. An impact threshold matrix was developed to ensure consistency when

assigning impact scores. The matrix contained the most common examples of each impact

for each receptor. Event descriptions must include the threshold criteria in order to be

designated as a significant event. A score multiplier was added after the impact scoring.

This took into account the age of the flood event and ensured that events were more fairly

scored given the changes in, for example, building standards. Any event which had a Very

High Impact was deemed to be Significant. Where significant flood events occurred within

an APSFR, it was considered that significant adverse consequences of similar future flood

events may be envisaged. The PFRA in Scotland concentrated on flooding from rivers, the

coast and heavy rainfall with a further consideration of the influence of groundwater.

15 of 25

There is no mention of potential floods from impounded water bodies (e.g. reservoirs or

canals) or natural lakes or specifically of flooding from sewers. No reasons were found

why they were not considered. Scotland has subsequently indicated that natural lakes were

part of the fluvial network for which flood extents were developed.

In England and Wales reservoirs below 10,000m³ in capacity were considered as unlikely

to present significant flood risks in the context of implementing the requirements of the

Floods Directive. In addition the Lead Local Flood Authorities (LLFAs) do not need to

assess flooding from sewers, unless wholly or partly caused by rainwater or other

precipitation entering or otherwise affecting the system. Floods of raw sewage caused

solely, for example, by a sewer blockage do not fall under the national Regulations

implementing the Floods Directive. The Regulations also do not apply to floods from

water supply systems, e.g. burst water mains, Snow melt and tsunamis. Snowmelt would

count as precipitation and so could lead to surface runoff. Tsunamis are considered as a

form of flooding from the sea. LLFAs also did not include past floods of a kind that are not

likely to occur now due to improvements in drainage or flood risk management measures.

In Northern Ireland an initial review of historical flooding was undertaken to scope the

potential risk from all flood sources. From this it was concluded that the main flood

sources likely to give rise to significant flooding were rivers, the sea, surface water runoff

and impounded water bodies (such as dams and reservoirs). However, the flood risk from

impounded water bodies was not conclusively assessed in the PFRA as there was at the

time insufficient ‘available or readily available’ information to conduct a robust

assessment of the risk from this source. The reason for this lack of information is that NI

does not have legislation for the management of reservoir safety and as a consequence the

owners of impoundments have not been required to collate such information as would be

necessary to assess the potential risk of their failure. NI will address this risk through the

introduction of new reservoir safety legislation. It is stated that Groundwater flooding is

insignificant in Northern Ireland compared with fluvial, coastal and pluvial flooding. As a

consequence it was decided not to explore the development of predictive flood models for

this source.

The only sources of flooding considered to be of potential significance in Gibraltar were

from the sea and from surface water run-off. Neither of these was considered to represent a

significant risk. Flooding from the two groundwater bodies in Gibraltar was also

considered but because of their hydrological characteristics they were not considered as

being relevant. A strategic assessment of the drainage and sewerage network within the

Gibraltar RBD was additionally used to assess the level of flood risk.

Question 8: What types of flood were not considered at all, and why?

Summary assessment

16 of 25

In Scotland it appears that flood from impounded water bodies (e.g. reservoirs or canals),

natural lakes and from sewers were not considered. No reasons for this were found. In

England and Wales all types of flood except from natural lakes seem to have been

considered. England and Wales has subsequently indicated that it is included in the flood

maps but is not considered a separate source of flooding. From the reported information

for Northern Ireland it is not clear whether canals are included in and considered as part of

impounded water bodies. Natural lakes such as Lough Neagh were also not mentioned.

Flooding from sewers is also not described as a potential source of flooding. Rivers do not

occur on Gibraltar, hence this source was not considered. It is not known whether or not

impounded water bodies occur in Gibraltar; no mention was made of them in the WISE

reports.

Question 9: What criteria were used to define an adverse consequence?

Summary assessment

In Scotland the following receptors of flooding were considered:

Human Health (A) People: No. of People/social flood vulnerability;

Human Health (B) Community: Community facilities that could cause community

disruption if affected by flooding

Economic Activity (A) Businesses: No. of business properties and the estimated

damages;

Economic Activity (B) Transport: Roads, railways and airports;

Economic Activity (C) Agriculture: Agricultural land and forestry areas;

Environment: Designated Areas and the susceptibility and resilience of the

species/habitats to the impacts of flooding;

Cultural Heritage: the importance of cultural sites exposed to flooding.

The criteria that defined an adverse consequence on each receptor were not reported to

WISE. Scotland has subsequently indicated that flood risk was calculated as a product of

likelihood, hazard, vulnerability, exposure and value.

The other aspects required to be considered under Article 4.2.d (hydrological and

geomorphological characteristics; effectiveness of existing manmade flood defence

infrastructures; climate change; future land planning) were included in the PFRA.

In England and Wales Lead Local Flood Authorities (responsible for pluvial, groundwater

and minor watercourse flooding) used the following flood risk indicators to assess the

potential adverse consequences of future flooding. Human health; number of people

affected, number of critical services; Economic activity; number of non-residential

properties, infrastructure network (length of roads and rail), and area of agricultural land;

Environment and heritage, the consequences of pollution, the impact on internationally and

nationally designated environmental sites, and the impact on internationally and nationally

17 of 25

designated heritage assets. It is assumed that “consequences of pollution” might include

any effect on water body status (i.e. WFD status).

Elements representing the topography, the position of watercourses and their general

hydrological and geomorphological characteristics, including floodplains as natural

retention areas were also included in the modelling for future potential floods. The position

of populated areas, areas of economic activity were also described. The criteria that

defined an adverse consequence on each receptor were not reported to WISE. No

equivalent information was reported to WISE for the other sources of floods for which

England and Wales is applying Article 13.1.b. However, as the authority responsible for

these other sources of flooding (Environment Agency of England and Wales) provided

guidance to the LLFAs in producing PFRAs, it seems likely that the same approach and

criteria would have been applied.

In Northern Ireland a GIS application was developed to combine the flood extent outlines

with a wide range of receptor datasets. Embedded within the application is a Flood Risk

Query Tool which applies algorithms to the data to quantify the flood risk in terms of flood

risk indicators. A broad range of flood risk indicators have been generated to measure the

adverse impact of potential flooding on groups of receptors on an average annual basis.

For example there are Flood Risk Indicators that quantify the annual flood risk in terms of

the number of people and their vulnerability, the number of properties (and their various

types), the number of key services, the length of key transportation infrastructure flooded,

the economic damages, the areas of environmental sites inundated, the number of

Integrated Pollution Prevention and Control sites and the number of nationally important

cultural heritage sites (i.e. Listed Buildings, Gardens, Sites and Monuments Records and

Sites of Archaeological Interest). An example of a key flood risk indicator is the

Aggregated Average Annual Damage (AAAD). This is the estimated average economic

damages arising from all sources of flooding which, taken over the very long-term, is

likely to occur on an annual basis.

The Flood Risk Indicators are supported as necessary by information on the vulnerability

of particular receptors. For example, UK census data was used to identify more vulnerable

populations, such as conglomerations of elderly population. The spatial distribution of the

Economic Deprivation Index computed by the Northern Ireland Statistical Service was

computed for flooded properties and used in the assessment of the vulnerability of people

to flooding. The criticality of key infrastructure and designated environmental sites

susceptible to flooding was determined through a broad ranging consultation exercise that

included the owner/operators of the asset owners and the NI Environment Agency. The

criteria associated with the Flood Risk Indicators that defined an adverse consequence on

each receptor were not reported to WISE.

In Gibraltar the criteria used to identify and assess significant flood risks included, but

were not limited to public health impacts, damage to property and infrastructure, number

of people affected along with the impacts of pollution. These were considered to be the

main indicators that are applicable to Gibraltar. Gibraltar did not identify any areas that

18 of 25

they considered to be at a significant flood risk but areas of land were identified that might

become inundated during flooding events from storm (sea) surges or heavy rainfall, but

where significant damage is unlikely to occur.

Question 10: What adverse consequences were excluded or not considered, and what were the

reasons for their exclusion?

Summary assessment

None seem to have been excluded in Scotland’s PFRA (WISE and downloaded

documents).

In England and Wales the LLFAs may not have considered some of the issues identified

under Article 4.2(d) in some of the future flood information where it was considered not

appropriate, or the information was not available, for assessment of local flood risk. For

example, the broad scale modelling of local flood risk has limited or no readily available

or derivable information about the effectiveness of existing manmade infrastructure. In the

case of surface water infrastructure it is usually a matter of very small local interventions,

including elements of the drainage and pumping network, or even variations in kerb

heights or the camber of a road that can influence the effectiveness of drainage.

For future floods such as the Areas Susceptible to Groundwater Flooding, and some local

future flood information, no automatic analysis was available about the position of

populated areas, and areas of economic activity as contained within the Environment

Agency's National Receptor Dataset. For groundwater LLFAs made their own assessment

of the impacts from local knowledge or overlaying with other maps of spatial information.

The influence of geomorphology was considered in the PFRA (PFRA document) for

Northern Ireland and an activity index was generated and based on land cover, drift

geology and stream-power with validation based on inspecting digital terrain /

photography images. Reaches with the greatest potential for geomorphological activity

that might affect flood risk were highlighted. However, the analysis was a broad-scale

approach and more site specific detailed studies of deposition and flood risk would be

required. Given the uncertainty associated with the approach used it was concluded that

geomorphology should not be considered further when assessing the potential

consequences of future floods. However, geomorphology data will be taken into account

when options are being considered for flood risk management plans.

Flood defence infrastructure has been ignored in the predictive modelling of future

flooding in Northern Ireland. This is a precautionary approach because there are

uncertainties regarding the levels of protection that flood defences would provide in

practice given the detailed information and analysis required for proper assessments.

19 of 25

There is little detailed information in the PFRA downloaded document for Gibraltar. The

text implies that adverse impacts on human health, economy, environment and cultural

heritage have been considered.

Question 11: What methods were used to identify and quantify potential future adverse

consequences and impacts?

Summary assessment

In Scotland a 1 in 200 year indicative river and coastal flood extents were used for the

PFRA. These represent the floodplains as natural retention areas. National pluvial and

groundwater datasets were also developed and integrated into the PFRA. An annual

exceedance probability factor of 0.5 was applied. Pluvial flooding extents were generated

using a 0.1 m and 0.3 m depth contours for use within the assessment. Each receptor was

assessed in terms of exposure to flood hazards, and also the characteristics of receptors

(i.e. the value/vulnerability to impacts of flooding). A 1km² grid approach was adopted

where grid cells were attributed with a risk score depending on the characteristics of the

receptors within the cell. A grid output was created for fluvial, coastal and pluvial flood

sources, for each receptor category, these were combined to provide a total score per cell.

A groundwater factor was then included for areas which had been classified to have a High

or Very High susceptibility to groundwater flooding.

A quantitative method was then used for translating the grid output to a higher geographic

level called the sub catchment unit (SCU). This summed the scores of all the cells within

each SCU and categorised the SCUs from Very Low to Very High. Additional information

only relevant or applicable at the catchment scale was then included in the analysis.

Flood defences were considered in a 2 phase process: the 1st phase identifies the

protection offered by defences; the 2nd phase is a manual, qualitative assessment of the

area behind a defence and the potential benefit offered- both are carried out at the SCU

level. The results of the assessment of historic floods was used to validate the grid output,

ensuring that significant past flood events have been identified and analysed to inform the

categorisation of SCUs and the definition of Potential Vulnerable Areas (PVA). All SCUs

categorised as Very High, High or Medium categories were included as PVAs.

The receptor groups used in the PFRA for the identification of flood risk areas in Scotland

were: 1. Human Health (A) – People (No. of Residential Properties and the social

vulnerability of the area); 2. Human Health (B) - Community (Important facilities that

could cause community disruption if affected e.g. schools, hospitals); 3. Economic

Activity (A) - Businesses (No. of business properties and the estimated weighted annual

average damage related to the property); 4. Economic Activity (B) - Transport (Roads,

railways and airports); 5. Economic Activity (C) - Agriculture (Agricultural land and

forestry areas); 6. The Environment (Areas designated for natural heritage purposes and

their vulnerability to flooding); and, 7. Cultural Heritage (Cultural sites such as UNESCO

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World Heritage Sites). The receptors were assessed using risk categories from Very Low

to Very High.

A large range of thresholds and methods have been tested to ensure that that the resulting

categorisation most accurately represents flood risk in Scotland. These are described in

detail in “Flood Risk Management (Scotland) Act 2009 (FRM Act), National Flood Risk

Assessment Methodology, Scottish Environment Protection Agency”, downloaded from

internet.

The main source of information about future floods in England and Wales is in the form of

maps produced by computer models. National maps of surface water flooding called the

Areas Susceptible to Surface Water Flooding (AStSWf) and the Flood Map for Surface

Water (FMfSW) include elements representing the topography, the position of

watercourses and their general hydrological and geomorphological characteristics,

including floodplains as natural retention areas.

The position of populated areas, areas of economic activity are described by the

Environment Agency's for England and Wales National Receptor Dataset, and analysis of

FMfSW and AStSWF were informed by this. The FMfSW contains two rainfall events,

divided into two depth bandings: 1 in 200 rainfall and 1 in 200 rainfall deep, as well as 1 in

30 rainfall and 1 in 30 rainfall deep. The AStSWF dataset contains one rainfall event, with

three susceptibility bandings: less, intermediate and more.

Some Local Lead Flood Authorities (responsible for pluvial, groundwater and flooding

from minor water course etc) were also able to use other future flood scenarios produced to

assess the impact of local sources of flooding from past studies of specific areas. National

maps of river and sea flooding were available in addition to the surface water maps to

assess potential areas where different sources of flooding could interact. Information about

potential groundwater flooding was provided from Areas Susceptible to Groundwater

Flooding map to help assess areas where this type of flooding could pose an additional

risk. Using the available maps and data sets, LLFAs were able to assess the potential

adverse consequences of future flooding.

The Environment Agency of England and Wales provided a very broad scale map showing

groundwater flood areas on a 1km² grid, called "Areas Susceptible to Groundwater

Flooding". This was deemed sufficient for the PFRA where no local information exists.

There are no Environment Agency products that deal solely with flooding from ordinary

watercourses, however the national surface water maps, and the Flood Map for rivers and

sea (for which the Environment Agency of England and Wales is responsible) contain

some relevant information, and so were included in PFRAs. Where additional information

about future flooding from ordinary watercourses exists locally, it was recorded in the

PFRA.

In England and Wales Defra and the Welsh Assembly Government provided guidance

(Selecting and reviewing Flood Risk Areas for local sources of flooding: Guidance to

Lead Local Flood Authorities Flood Risk Regulations 2009, Department for Environment,

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Food and Rural Affairs, 2010, downloaded from the internet) to the LLFAs on the

indicators and thresholds to be used to determine the indicative Flood Risk Areas

equivalent to where there is a significant flood risk in their area. Flood Risk Areas are

where flood hazard and risk maps and flood risk management plans compliant with the

Floods Directive will be prepared. In determining the criteria, the consequences of

flooding to people are considered the most important. For example, the threshold for the

number of people (based on number of residential properties x 2.34) at risk was set at

30,000 for England and 5,000 for Wales (because of predominantly smaller settlements in

Wales), and for the number of critical services (including schools, hospitals, nursing

homes, power and water services) 150 in England and 25 in Wales although number of

people is the deciding threshold for indicative Flood Risk Areas. The assessment was

based on flooding to a depth of 0.3 metres by a rainfall event with a chance of 1 in 200 of

occurring in any given year (equivalent to 'in the order of' 1 in 100 annual probability of

flooding).

In Northern Ireland it was considered to be not appropriate to identify and assess ‘potential

future significant floods’ as this presupposes that only floods exceeding a particular

magnitude are deemed to be significant and takes no account of the periodicity of floods. It

was thought more appropriate to identify the significance of the total flood risk in discrete

areas in a manner that takes account of the adverse consequences of the whole spectrum of

floods which range in magnitude and periodicity. The future flood risk is assessed using a

GIS based Source – Pathway Receptor model that combines the output from predictive

flood models with a digital terrain model and a host of readily available receptor datasets.

The assessment of the potential adverse consequences of flooding is based on three

different probability events (low, medium and high) for each of the flood sources. By

producing flood outlines with different return periods it was possible to ‘annualise’ Flood

Risk Indicator values to produce estimates of the adverse effects that best represent the

true long term annual average.

The Annual Exceedance Probability of the events used in the assessment for each source is

fluvial: 10%, 1% and 0.1%, coastal; 10%, 0.5% and 0.1% and pluvial 10%, 0.5% and

0.1%. The GIS application identifies the receptors that are spatially intersected by flood

outlines for the high, medium and low probability flood events for each of the flood

sources. Embedded within the application is a Flood Risk Query Tool which applies

algorithms to the data to quantify the flood risk in terms of flood risk indicators.

A broad range of flood risk indicators have been generated to measure the adverse impact

of potential flooding on groups of receptors. The flood risk indicators included the:

Number of different building types located within any flood outline; Number of flooded

key services split into different categories and totalled; Number of people at risk (number

of flooded residential buildings times 2.5 people per dwelling); Number of IPPC sites

flooded and the area of IPRI site polygons flooded; Length of key infrastructure flooded

(roads); Area of flooded buildings; Area of flooded ASSI; Vulnerability based on census

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data; Economic Deprivation; Property damages of flooded buildings; and Agricultural

damages.

The long-term annual average values of all these indicators was computed for fluvial,

coastal and pluvial flooding by integrating the indicator (i.e. damage) versus probability

curves. These quantitative indicators are used in whole or in part to assess the potential

flood risk in the broad categories required by the Directive; i.e., human health, economic

activity, cultural health and the environment. The suite of flood risk indicators are

measured in 1km grid squares. By computing the flood risk indicators at this spatial level

it is possible to use them to compare and contrast the risk across Northern Ireland at a

broad community scale.

There has been no modelling of flooding in Gibraltar and therefore the information used in

the PFRA has been derived from an assessment of the water bodies in the Gibraltar RBD

and from anecdotal evidence obtained by the Department of the Environment.

Question 12: What long term developments were considered, what methods were used and what

were the expected impacts on the occurrence of potentially significant future floods?

Summary assessment

In Scotland a project was undertaken to assess the vulnerability of Scotland’s river

catchments and coasts to the impact of climate change. The method for rivers used an

estimate of a catchment’s sensitivity to climatic change then combined it with information

on climatic hazard in order to estimate the risk in terms of the impacts on peak river flows.

Catchment sensitivity (response type) was estimated from each catchment’s properties.

This approach is intended to be scenario-neutral (i.e. based on catchment response rather

than the time-varying outcome of individual (climate change) scenarios) in order to

provide a strong base assessment of the potential impact of climate change and thus secure

confidence in setting future objectives and measures to manage flood risk. The coastal

approach included the definition of climate change predictions, coastal behaviour systems

and associated sensitivity analysis, identification of assets exposed to hazards and finally

an assessment of coastal vulnerability. A factor relating to the potential impacts that

climate change would cause was applied to each catchment unit. The factor is based on the

increase in economic costs which would be expected due to a greater flooding depth to

identified receptors. The factor does not include additional receptors being placed in the

floodplain.

Future strategic developments are also considered in Scotland. These were obtained from

the Scottish Government’s long term spatial strategy for Scotland's development. This sets

out a commitment to an integrated approach to water management including flood risk

management. The potential increase in flood risk as a result of climate change is

recognised and recommends that available flood maps are utilised to inform decisions on

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the appropriate locations of new build developments. Data identifying the locations of

these strategic areas of development has been created. The types of developments included

are national scale and include regeneration projects, large residential developments and

infrastructure improvements. This data has been used in combination with other

information such as climate change impacts, to aid in the definition of potential vulnerable

areas.

Studies have been undertaken to develop information (Key Projections) and implications

for flood risk for each River Basin District (RBD) in England and Wales on climate

change and long term developments based on the most recent UK Climate change

predictions study, UKCP09. The Lead Local Flood Authorities have included and used the

projections relevant to the RBD and its area to inform the PFRA on the sources of flooding

they are responsible for. It is implied in the “Flooding in England: A national assessment

of flood risk” report (there is an equivalent report for Wales) that the same approach is

used by the Environment Agency in the assessment of flood risk from the sources for

which it is responsible.

All English PFRAs produced by the LLFAs include a short description of the current

planning policy for England, which aims to prevent new building and infrastructure

development from increasing flood risk. Planning policy for England is likely to be

revised in 2012. In England, Planning Policy Statement 25 (PPS25) on development and

flood risk aims to "ensure that flood risk is taken into account at all stages in the planning

process (the process by which developers obtain permission to carry out development) to

avoid inappropriate development in areas at risk of flooding, and to direct development

away from areas at highest risk.

Where new development is exceptionally necessary in such areas, policy aims to make it

safe and sustainable without increasing flood risk elsewhere and where possible, reducing

flood risk overall." Local Planning authorities administer the planning process and rely on

statutory consultees such as the Environment Agency and Water Companies as well as

Strategic Flood Risk Assessments for their area (SFRAs) to inform their decisions about

potential flood risks. Adherence to Government policy should ensures that new

developments do not increase local flood risk. In exceptional circumstances the Local

Planning Authority may accept sustainable development that increases flood risk, usually

because of the wider benefits of a new or proposed major development. Any exceptions

would not be expected to increase risk to levels which are "significant" (in terms of the

Government's criteria). In Wales, Technical Advice Note 15 (TAN15) on development and

flood risk sets out a precautionary framework to guide planning decisions. The overarching

aim of the precautionary framework is "to direct new development away from those areas

which are at high risk of flooding."

In Northern Ireland models have been used to estimate the potential increase in flood risk

arising from climate change. The climate change sensitivity of the fluvial and coastal

flood risk was assessed by calculating the values of the annualised key flood risk

indicators using the predicted flood outlines for the low, medium and high probability

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events relevant to the year 2030. The data used in the models for the year 2030 is

consistent with the increased rainfall predictions published in UKCP09. The values of the

flood risk indicators calculated for the year 2030 is contrasted with the ‘present day’

values at the 1km grid and sub-plan area scales to identify the geographical areas that are

particularly sensitive to the potential future impacts of climate change.

The climate change sensitivity for pluvial risk was assessed in a similar manner, except

that the 2100yr (climate change) outlines were used and not the 2030 yr. The risk arising

from potential land-use changes to catchments and coastal areas, particularly in relation to

the construction of new development has also been considered in Northern Ireland.

Planning Policy Statement 15 on Planning and Flood Risk has the aim of preventing future

development that may be at risk of flooding or that may give increase the risk of flooding

elsewhere. The climate change flood maps used in the PFRA are considered by the

Planning Service in the preparation of regional development plans and lands within flood

plains will not, save in exceptional circumstances, be included in future development

zones.

The Gibraltar Climate Change Programme (2008) which is currently being revised states

that the predicted effects of climate change in the Western Mediterranean are expected to

include lower levels of rainfall and a change in the distribution and intensity of rainfall.

This means that rainfall storms may become heavier leading to an increase in flooding.

The extent of flooding in the areas currently at risk could potentially increase therefore

with higher intensity rainfall events. If rainfall intensities increase, future flooding in the

town areas could affect some transport routes and cause damage to ground floors of offices

and residential buildings. Flooding events could also be affected in the future from the

potential impacts of climate change such as changes in sea level. The Gibraltar Climate

Change Programme (2008) indicates that a predicted increase in sea level in the order of

0.48m by 2100 is a reasonable figure to be applied to Gibraltar based on best estimates of

between 0.28 and 0.58m above 1989 to 1999 sea levels. All replacement sea defences

have taken account of potential sea level rise from climate change impacts so that the

height of the all new and upgraded sea walls are greater than predicted future sea levels.

There is no mention of potential changes in land use or planning being considered in the

PFRA.

Number of identified Areas of Potential Significant Flood Risk

Table 6 Areas of Potential Significant Flood Risk (APSFR) and types of consequences

Source: WISE Flood aggregation report: “FD 7.1 Areas of Potential Significant Flood Risk”

Member

State

Source

Mechanism

Characteristics Number

of

APSFR

Number with reported consequences

Human

Health

Environment Cultural

Heritage

Economic

Activity

UK Fluvial, 97 152 47 76 261

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Pluvial

UK Fluvial,

Pluvial, Sea

water

161 263 124 143 456

UK Pluvial Natural

exceedance

Medium onset

flood

18 18 7 8 16

UK Pluvial, Sea

water

5 7 2 4 13

More than one type of consequence can be reported for each aggregated consequence (e.g. economic activity) for

each flood event, and therefore the totals in the consequence cells may be greater than the total number of flood

events reported for each type of flood

International coordination

MS were required to report how international cooperation had been achieved when undertaking a

PFRA under Article 4; and also for APSFR under Article 5. Those applying Article 13.1.a are

expected to have coordinated cooperation in the identification of APSFR but not necessarily for

the PFRA.

The relevant articles are:

Article 4. 3. In the case of international river basin districts, or units of management referred to in

Article 3(2)(b) which are shared with other Member States, Member States shall ensure that

exchange of relevant information takes place between the competent authorities concerned. And;

Article 5.2. The identification under paragraph 1 of areas belonging to an international river basin

district, or to a unit of management referred to in Article 3(2)(b) shared with another Member

State, shall be coordinated between the Member States concerned.

Number of international UoMs in the UK: 2

Number of non-international UoMs in the UK: 14

Table 7 Mechanisms of international coordination for preparation of PFRAs and

APSFRs

Type of coordination Number of UoMs

PFRAs APSFRs

International coordination and working groups – responsible for advice, decision-making, coordination, progress of work and/or implementation

2 2

Informal arrangement (groups, discussions and exchange of information)

2