MERTHYR TYDFIL COUNTY BOROUGH COUNCIL Civic Centre, Castle Street, Merthyr Tydfil, CF47 8AN

Main Tel: 01685 725000 www.merthyr.gov.uk

SCRUTINY REPORT

Date Written 17th June 2011 Report Author Howard Jones Service Area Scrutiny Exempt/Non Exempt Non exempt Committee Date 18th July 2011

To: Scrutiny members,

Scrutiny - The Flood Risk Regulations 2009, Preliminary Flood Risk Assessment Report. PURPOSE OF THE REPORT: To update Scrutiny Members on the Council’s progress on the Preliminary Flood Risk Assessment (PFRA) as required by the Flood Risk Regulations 2009, as reported to Cabinet on 8th June 2011 (APPENDIX I).

1.0 INTRODUCTION AND BACKGROUND 1.1 Members of the Committee will be aware from previous meetings with the

Assistant Director Technical Services (EF) that this Authority was required under the Flood Risk Regulations 2009 to submit a Preliminary Flood Risk Assessment (PFRA) to the Environment Agency by June 2011.

1.2 Prior to submitting the PFRA to the Environment Agency, Scrutiny had a role in

reviewing the Assessment (between January and June 2011) to ensure it met the required quality and consistency standards.

1.3 However as reported by the Assistant Director Technical Services to this

Committee, due to the delays in receiving guidance from the Environment Agency and the tight deadline to submit the PFRA to Cabinet, it was likely that Scrutiny would only be able to receive the Assessment retrospectively i.e. after it had been submitted to Cabinet for approval and also after it had been submitted to the Environment Agency.

1.4 The PFRA covering report was submitted to Cabinet on 8th June 2011 (see

APPENDIX I) and the recommendations therein were approved. One of the recommendations was that “The Preliminary Flood Risk Assessment Report be referred to the appropriate Scrutiny Committee (Schools & Technical Services) as required by the Environment Agency”. For the “Merthyr Tydfil County Borough Council - Preliminary Flood Risk Assessment Report PFRA”, see APPENDIX II.

1.5 To aid review and scrutiny of PFRA the Environment Agency1 has provided a

number of questions which Scrutiny members may wish to consider. The questions have been supplemented with a summary response by the directorate.

a) Are appropriate governance arrangements in place to understand and

manage local flood risk? Cabinet Customer Services Schools and Technical Portfolio Holder – Cllr Richard Thomas Director of Customer Services – Gary Thomas, Assistant Director (Technical Services & Regeneration) – Edward Foley, Officers – Kevin Davies, Michael Williams (Engineering), b) Have the relevant internal and external partners been involved in the PFRA process? The external partners involved in the process include – Environment Agency, British Waterways, Network Rail, Dwr Cymru/Welsh Water, Internal Drainage Board, South Wales Fire and Rescue and South Wales Trunk Road Authority. c) Has all readily available information been gathered from within the LLFA and other partners? Each organisation outlined above was contacted for information. The assessment has been undertaken using all known available data and the limitations of this data is clearly noted. d) Does the assessment of flood risk identify the receptors and the consequences in terms of human health, economic activity and the environment (including cultural heritage)? This can be found in Chapter 3 of the report (SEE APPENDIX II). e) Has the evidence been interpreted appropriately in reviewing indicative Flood Risk Areas? The assessment has used the available data, identifying its limitations and has complied with the ministerial definition of significant flood risk. f) Has adequate justification been provided for changes to indicative Flood Risk Areas? This can be found in Chapter 7 of the report. (SEE APPENDIX II). g) Is there sufficient evidence to support Flood Risk Areas? The assessment has been undertaken using all known available data, the limitations of this data is clearly noted. h) Are the conclusions and recommendations clear and based on suitable evidence? These can be found in Chapter 7 of the report. (SEE APPENDIX II).

1 Preliminary Flood Risk Assessments. Final Guidance (December 2010)

i) Have the preliminary assessment report and associated spreadsheets been prepared in line with the templates in the guidance? The officer level review has checked the report against the template set out in the guidance. The spreadsheet has not been amended and the compulsory fields completed.

2.0 CONCLUSIONS 2.1 The Environment Agency has produced a guidance document which has been

used by local authorities to prepare their PFRA’s. The main purpose for Scrutiny is to ensure that the PRFA and associated document are fit for purpose in meeting the requirements of the Flood Risk Regulations.

2.2 The PFRA report was approved by Cabinet on 8th June 2011. Ideally Scrutiny

should have had input to the report at draft stage rather than retrospectively. 2.2 To aid review and scrutiny of the PFRA the Environment Agency has provided a

number of questions which members of the committee may wish to consider and these are shown in 1.6 above.

3.0 RECOMMENDATION(S) 3.1 That the Committee notes the content of this report when reviewing the

Preliminary Flood Risk Assessment Report. BACKGROUND PAPERS Title of Document(s) Document(s) Date Document Location As per page references

MERTHYR TYDFIL COUNTY BOROUGH COUNCIL Civic Centre, Castle Street, Merthyr Tydfil, CF47 8AN

Main Tel: 01685 725000 www.merthyr.gov.uk

CABINET REPORT

Date Written 24th May 2011

Report Author Kevin Davies

Service Area Engineering, Highways and Transport

Committee Division Portfolio

Committee Date 8th June 2011

To: Chairman, Ladies and Gentlemen

The Flood Risk Regulations 2009 – Preliminary Flood Risk Assessment Report. PURPOSE OF REPORT: To inform councillors of the Council’s statutory obligations in relation to the Flood Risk Regulations 2009 and to seek approval of the “Preliminary Flood Risk Assessment Report” prior to its submission to the Environment Agency (Wales).

1.0 INTRODUCTION AND BACKGROUND

A. THE FLOOD RISK REGULATIONS 1.1 The Flood Risk Regulations 2009 results from European wide legislation and is meant to provide a high level strategic review of flooding throughout all European countries. 1.2 Under the Flood Risk Regulations 2009 Merthyr Tydfil County Borough

Council has been designated as a Lead Local Flood Authority (or LLFA). As such it has a responsibility to produce various documents over the next 5 years, as listed below.

Stage Lead Deadline

First Cycle

PFRA preliminary assessment report completed and Flood Risk Areas determined

LLFA 22 June 2011

PRFA preliminary assessment report and Flood Risk Areas reviewed and finalised

EA 22 December 2011

PRFA preliminary assessment report and Flood Risk Areas published

EA 22 December 2011

APPENDIX I

Flood risk maps and flood hazard maps LLFA 22 June 2013

Flood risk maps and flood hazard maps reviewed

EA 22 Dec 2013

Flood risk maps and flood hazard maps published

EA 22 Dec 2013

Flood risk management plans LLFA 22 June 2015

Flood risk management plans reviewed EA 22 Dec 2015

Flood risk management plans published EA 22 Dec 2015

Second cycle

First Review – PRFA is updated or revised LLFA 22 June 2017

PFRA review EA 22 Dec 2017

1.3 Regulation 14 of the Flood Risk Regulations describes the

methodology for identifying areas of significant flood risk, known as Flood Risk Areas. Where such areas have been identified by the Environment Agency (EA) the LLFAs are required to prepare Preliminary Flood Risk Assessments Reports followed by flood hazard/risk maps and flood management plans compliant with the Regulations. In determining the criteria, the impact of flooding to numbers of people is considered the most important criteria.

B. INDICATIVE FLOOD RISK AREAS 1.4 The indicative Flood Risk Areas were identified by the Environment

Agency by drawing on national flood risk information to identify 1 kilometre grid squares where “local flood risk is an issue”. Where many grid squares are close together (clustered) and the risk is most concentrated, these clusters are identified as indicative Flood Risk Areas. To qualify as a Flood Risk Area within Wales a cluster must have a population of at least 5,000 people.

1.5 As a LLFA Merthyr Tydfil County Borough Council has reviewed the

indicative flood risk area and amended it to form the MTCBC Flood Risk Area. This has been done on the basis of local flood risk information and forms the basis of our Preliminary Flood Risk Assessment Report.

1.6 Our observations on the indicative Flood Risk Areas are evidence

based and are related to historic flooding. The most significant flooding event for which MTCBC has recorded data is the flood of December 1979. In that flood the number of properties flooded within the borough was 146 and on the basis of the EA multiplier of 2.34 for the average number of resident in each property 341 people were affected. This represents a flood event at least one level of magnitude below that of 5,000 which is used to determine a Flood Risk Area within Wales.

C. MAPS, PLANS AND FUTURE REVIEW 1.7 Following the completion of the preliminary assessment reports and

identification of Flood Risk Areas, LLFAs will be required to prepare

maps and plans of all flood risk areas. Flood hazard maps and flood risk maps are required by 22 June 2013 and flood risk management plans by 22 June 2015.

1.8 Flood hazard maps and flood risk maps will be based on the published Flood Risk Areas. 1.9 These hazard maps are to show the potential extent of the

consequences, including direction and speed of flow, and the probability of occurrence. The Risk Maps are to show the number of people at risk, economic and industrial activities and protected areas affected as well as impact on water quality.

1.10 The Environment Agency are to provide guidance by Jan 2012 for these. D. PRODUCE FLOOD RISK MANAGEMENT PLANS. 1.11 Management Plans are to cover the objectives and measures relating

to the prevention of flooding, protection of individuals, communities and the environment and arrangements for forecasting and warning. Also to consider Flood Management Actions and resilience measures.

These plans must be prepared by the LLFAs by 22 June 2015

2.0 FINANCIAL IMPLICATIONS 2.1 As funding has been made available by the Welsh Assembly

Government for this initial phase there are currently no financial implications associated with the production of the reports and plans. However there has been no guarantee that similar funding will be available for the next phases, ie beyond December 2011.

3.0 CONCLUSION

3.1 Using the indicative flood risk area maps provided by the Environment Agency (Wales) as a starting point the Council’s Drainage Team has produced the document entitled “Merthyr Tydfil County Borough Council” – “Preliminary Flood Risk Assessment Report”.

Because of the size of the report it is included in the Councillor Library

and entitled “Preliminary Flood Risk Assessment Report”. 3.2 This document outlines the general principles and the support

information which have been used to determine MTCBC’s Preliminary Flood Risk Assessment.

4.0 EQUALITY IMPACT ASSESSMENT 4.1 The document is an overarching strategy based on guidelines and

parameters set by European Directives. An Equality Impact Assessment has been considered relating to this document and no negative effects have been identified at this stage.

4.1 Further Regulations will be prepared in the future and those documents

will consider Equalities Impact in more detail

5.1 RECOMMENDATIONS that

5.1 In order to comply with statutory obligations, the said report be adopted as the Preliminary Flood Risk Assessment for the Merthyr Tydfil County Borough and that it be submitted to the EAW prior to the 22nd June 2011 deadline.

5.2 Further reports to be submitted to Cabinet outlining resource needs

identified for completion of the further statutory provision as guidance evolves.

5.3 The Preliminary Flood Risk Assessment Report be referred to the

appropriate Scrutiny Committee (Schools & Technical Services) as required by the Environment Agency.

GARY THOMAS DIRECTOR OF CUSTOMER SERVICES

BACKGROUND PAPERS

Title of Document(s) Document(s) Date Document Location

Flood Risk Regulations 2009 Flood event records

- various and ongoing

Departmental files Departmental files

Consultation has been undertaken with Executive Board in respect of

each proposal(s) and recommendation(s) set out in this report.

APPENDIX II

MERTHYR TYDFIL COUNTY BOROUGH COUNCIL

Preliminary Flood Risk Assessment Report (PFRA)

April 2011

Preliminary Flood Risk Assessment Report Executive Summary Under the Flood Risk Regulations (2009) and the Flood and Water

Management Act became law in April (2010) Merthyr Tydfil Council Borough

Council (MTCBC) has been identified as a Lead Local Flood Authority (LLFA)

and has been given a number of key responsibilities, including the preparation

of a Preliminary Flood Risk Assessment Report (PFRA).

To satisfy the Regulations MTCBC have identified a number of Partners

including The Environment Agency Wales (EAW), Dwr Cymru / Welsh Water

and the emergency services from outside of the Authority and Emergency

Planning Section, Planning Section, Highways Division and Land Drainage

Division within the Authority. Significant quantities of data have been collected

from these partners.

The Environment Agency has identified an indicative Flood Risk Area within

MTCBC of 45 km2. This area has been reviewed by MTCBC using all the

information collected and consequently the Flood Risk Area has been increased

to 58 km2.

Preliminary Flood Risk Assessment Report Contents Page

Executive Summary 1 1 Introduction 3

2 Lead Local Flood Authority Responsibilities 5

3 Methodology and Data Review 7

4 Past Flood Risk 10

5 Future Flood Risk 12

6 Review of Indicative Flood Risk Area 14

7 Identification of Flood Risk Area 15

8 Next Steps 17

9 References 18

Figures Fig. 1 All Wales Map 20

Fig. 2 EAW Indicative Flood Risk Area and Blue Squares for MTCBC 21

Fig. 3 MTCBC Flood Risk Area and Blue Squares for MTCBC 22

Fig. 4 MTCBC Flooding Incidents and Historic Flooding 23

Fig. 5 MTCBC Blue Square X304Y207 24

Fig. 6 MTCBC Blue Square X307Y201 25

Fig. 7 Areas Flooded during December 1979 Flood 26

Fig. 8 MTCBC Flood Map for Surface Water 1 in 200 year 27

Tables Table 1 – Key Flood Risk Indicators 7 Table 2 – Data Collected 8

Table 3 – Details of the December 1960 Flood 11

Table 4 – Details of the December 1979 Flood 11

Annexes Annex 1 Record of past floods 19

Annex 2 Future floods 19

Annex 3 Flood Risk Area 19

Annex 4 Review checklist 19

Annex 5 – GIS Layer of Flood Risk Area 19

Appendices 1 Information for reporting on Flood Risk Area 20

Preliminary Assessment Report

1 Introduction

1.1 The Flood Risk Regulations came into force in December 2009 and the Flood and Water Management Act became law in April 2010. Under this legislation Merthyr Tydfil Council Borough Council (MTCBC) has been identified as a Lead Local Flood Authority (LLFA) and has been given a number of key responsibilities.

1.2 The purpose of the Flood Risk Regulations is to transpose the European Commission (EC) Floods Directive (2007/60/EC), on the assessment and management of local flood risk, into domestic law in England and Wales and to implement its provisions. In particular it places duties on the LLFAs to prepare a number of documents including:-

Preliminary Flood Risk Assessment Report 22nd June 2011 Flood Hazard and Flood Risk Maps 22nd June 2013 Flood Risk Management Plans 22nd June 2015

1.3 The purpose of this Preliminary Flood Risk Assessment Report is to identify areas subject to significant flood risk within Merthyr Tydfil County Borough Council. This information will then be used to inform the later stages of the Regulations including the Flood Hazard and Flood Risk Maps and the Flood Risk Management Plans.

1.4 It is the responsibility of the Lead Local Flood Authorities (LLFA) to consider the risk from the following sources:-

1. Ordinary watercourses 2. Surface runoff 3. Groundwater 4. And any interaction these have with drainage systems and other sources of

flooding.

The report does not consider flooding from main rivers, the sea or large raised reservoirs, which are the responsibility of the Environment Agency.

1.5 The area identified as being subject to significant risk is referred to as The Flood Risk Area. The PFRA report must consider floods which have significant harmful consequences for human health, economic activity and the environment.

1.6 Merthyr Tydfil County Borough Council (MTCBC) is a Unitary Authority situated within the valleys of South East Wales. It has a population of approximately 56,000 and an area of 11,189 hectares. The Borough is a mix of rural and urban communities generally built on the steeply sloping hillsides or within the valley basins.

See Fig 1. All Wales Map. 1.7 The study area is served by one water company – Dwr Cymru / Welsh Water and has

one major catchment which drains into the River Taff. 1.8 The PFRA is a high level screening exercise to locate areas in which the risk of surface

water and groundwater flooding is significant and warrants further examination through the production of flood hazard and risk maps and management plans.

The aim of the PFRA is to provide an assessment of the local flood risk across the

study area, including information on past floods and the potential consequences of future floods.

The key objectives may be summarised as follows:-

1. Identify relevant partners involved in future assessment of flood risk and summarise means of stakeholder engagement.

2. Describe arrangements for partnership and collaboration for the collection,

assessment and storage of flood risk data. 3. Provide a summary of the systems used for data sharing and storage, and

provision for quality assurance, security and data licensing arrangements. 4. Summarise the methodology adopted for the PFRA with respect to data

sources, availability and review procedures. 5. Assess historic flood events within the study area resulting from surface

water, groundwater and ordinary watercourses together with the consequences and impact of these events.

6. Collect and integrate historic information, which will be built upon in the

future and used to support and inform the preparation of the MTCBC Local Flood Risk Strategy.

7. Assess the potential harmful consequences of future flood events within the

study area. 8. Review the provisional national assessment of the Indicative Flood Risk

Area provided by the EAW and provide explanation and justification for any amendments required in order to produce the final Flood Risk Area.

2 Lead Local Flood Authority Responsibilities 2.1 In order to satisfy MTCBC’s governance procedures a preliminary report outlining the

requirements of the Flood Risk Regulations and the Flood and Water Management Act, and giving details of the responsibilities of MTCBC as a LLFA was presented to the Scrutiny Committee in March 2011.

The Preliminary Flood Risk Assessment Report, details of the Flood Risk Area and the Preliminary Assessment Report Spreadsheet will be placed before the Cabinet, full Council and Scrutiny Committee of Merthyr Tydfil Count Borough Council on prior to the final completion deadline of 19th August 2011.

2.2 As part of the PFRA MTCBC has sought to engage partners which includes those listed below:-

1. The Environment Agency Wales (EAW) 2. Dwr Cymru / Welsh Water (DCWW) 3. Local Emergency Services – including fire and police.

In addition significant collaboration has been stimulated between the various departments within MTCBC as listed below:-

1. Emergency Planning Section 2. Planning Section 3. Highways Division 4. Land Drainage Division.

In addition significant interaction and collaboration has been established with neighbouring LLFAs within South East Wales.

2.3 It is recognised that members of the public may also have valuable information to

contribute to the PFRA and the Local Flood Risk Strategy. Collaboration with the public can afford significant benefits including building trust, gaining access to additional local knowledge and increasing the chance of stakeholder acceptance of the local risk management plans.

To date the public have not been engaged on this project but the importance of collaboration is recognised. It is proposed that MTCBC will follow the guidelines outlined in the Environment Agency’s “Building Trust with Communities” publication which provides a useful process to communicate risk including the causes, probability and consequences to the general public and professional forums.

2.4 In addition to the Preliminary Flood Risk Assessment Report, Flood Hazard and Flood Risk Maps and Flood Risk Management Plans the Flood and Water Management Act and the Flood Risk Regulation have placed on Lead Local Flood Authorities a number of other significant responsibilities including the following:-

1. Investigating and recording flood incidents and significant flooding events - including the identification of which authorities have flood risk management functions and what they have done or intend to do with respect to the incident. Notifying the risk management authorities where necessary and publishing the results of any investigations carried out.

2. Maintain an Asset Register of features or structures which are

considered to have an affect on flood risk, including ownership and condition.

3. SuDS Approving Body (SAB) - to approve, adopt and maintain any new

sustainable drainage system. 4. Local Strategy for Food Risk Management - develop, maintain, apply

and monitor the strategy. 5. Work Powers - The LLFA have powers to undertake work to manage flood

risk. 6. Powers to Designate Structures which may affect flooding in order to

safeguard assets that are relied upon for flood risk management.

3 Methodology and Data Review 3.1 The following organisations were identified and contacted to obtain information for the

preparation of the PFRA:- Environment Agency – Wales GeoStore National Receptor Dataset Utilities Dwr Cymru/Welsh Water Western Power British Telecom Emergency Services Fire Service Police Within Merthyr Tydfil CB Council Planning Section Emergency Planning Section IT Section - GIS Land Drainage Division Highways Division

Table 1 - Key Flood Risk Indicators

Impact of flooding on Flood Risk Indicators Human Health Number of residential properties

Critical Services including hospitals, police, fire and ambulance stations, schools, nursing homes

Economic Activity Number of non-residential properties Length of road or rail Area of agricultural land

Cultural Heritage

Ancient Monuments Listed Buildings

Environmental

Designated sites – SSSIs and SINCs Nature reserves Landscape of historic interest

The above indicators have been selected by Defra, WAG and the Environment Agency

Wales in order to identify areas where flood risk and potential consequences exceed a pre-determined threshold. Indicative Flood Risk Areas have been identified where more than 5,000 people are at risk of flooding.

Table 2 – Data Collected

Data Description

Areas Susceptible to Surface Water Flooding

First generation national mapping, outlining areas of risk from surface water flooding with three susceptibility bandings - less, intermediate and more

Flood Map for Surface Water Second generation national surface water flood mapping which includes two sets of data - 1 in 30 and 1 in 200 year rain fall events with two bandings for each - greater than 0.1m and greater than 0.3m

Flood Zones Maps showing flood zones 2 and 3 Areas Susceptible to Groundwater Flooding

Coarse scale mapping showing areas susceptible to groundwater flooding

Historic Flood Map 22 Showing locations of areas of past flooding

National Receptor Dataset This data set gives details of social, economic, environmental and cultural receptors including residential properties, schools, hospitals, and electrical substations

EAW Blue Square Squares which the EAW have identified as being susceptible to flooding of significant consequences

Indicative Flood Risk Area Nationally identified flood risk area based on the Defra documentation

River network Map of main rivers Flood defences Location of existing flood defences and land protected Historic Sewer Flooding Location of incidents of fouls sewer flooding Historic Surface Water Flooding Location of incidents of surface water flooding

Cultural Coarse scale map of listed buildings and scheduled monuments at risk of flooding

Environmental Coarse scale maps of PPC sites with potential risk of flooding,

Envi

ronm

ent A

genc

y - W

ales

Historic landfill Areas used for land fill Welsh Water DG5 Register Incidents of flooding within properties and severe external

Welsh Water Services Location of pumping stations, service reservoirs and treatment works

Western Power Location of substations Util

ities

British Telecom Location of telephone exchanges

Fire Service Incidents of flooding

Emer

genc

y Se

rvic

es

Police Incidents of flooding

Land Drainage Division Incidents of flooding to property Areas of historic flooding

Planning Section - cultural Listed buildings, ancient monuments, Planning Section - environmental SSSI, nature reserve, SINC, landscape of historic interest IT Section - GIS Contours at 5m intervals Emergency Planning Section Incidents of flooding to property

Emergency Planning Section Location of schools, care homes, doctors surgeries, fire stations, police stations, ambulance stations, M

erth

yr T

ydfil

CB

Cou

ncil

Highways Division Highway classification and routes

3.2 Information from the Environment Agency Wales was readily available on CD, email and down loads from the EAW GeoStore. This information was in a form which allowed it to be easily imported into our GIS system.

Incidents of flooding from Dwr Cymru / Welsh Water were provided on request and were in a form which allowed easy importation into our GIS. Their asset location data which arrived much later was also received in a suitable electronic format. Locations of services from British Telecom and Western Power were in paper format with no grid references and therefore had to transposed into a form suitable for use in a computerised GIS. Flooding incidents from the emergency services were limited in number and in paper format without grid references. These data sets all had to be re-entered in electronic format. Flooding incidents from the Engineers were limited in numbers, in paper format and without grid references. This data had to be re-entered in electronic format. There are considerable gaps in this information where years of records have been misplaced. Further searches may reveal additional data during the preparation of the Local Flood Risk Strategy. Although this information is incomplete the data we have is considered to have a high confidence rating in terms of its reliability. The historic flooding areas have been identified from the personal knowledge of staff within the Drainage Section, and although incomplete, is it regarded as being of a high quality. Information from the Emergency Planning Section was in a format incompatible with GIS and therefore had to be transposed into a suitable electronic format. Information from the Highways Division and Planning Section was in electronic format and readily imported into GIS. It is the intension of MTCBC to gather more information on future flooding incidents which will be in electronic format suitable for importation into our GIS system.

3.3 We currently operate with ArcMap GIS system and all our information is now stored in electronic format suitable for importation as layers within ArcMap. For easy input of data we are currently using Microsoft Excel Spreadsheets and Microsoft Word as a word processor.

3.4 Although the amount of data recording past incidents of flooding and historic flooding is

limited, Fig. 4 MTCBC Flooding Incidents and Historic Flooding shows a high degree of correlation between these data sets and the Blue Squares identified by the EAW and MTCBC.

3.5 The information received from the EAW is restricted by the terms imposed by them.

Information provided by MTCBC on Ordinance Survey maps is subject to the normal licensing agreement with them. We are not aware of any other restrictions on the data available to MTCBC.

4 Past Flood Risk

4.1 Data of incidents of past flooding has been collected for this report as detailed in Section 3 above.

To decide on the significance of an individual flood Defra/WAG/EA have set key flood risk indicator which define a Flood Risk Area in Wales as having 5,000 people at risk or an individual 1km square where at least 200 people or 20 businesses or more than 1 critical service might be flooded to a depth of 0.3 metres and above by a rainfall event with a chance of 1 in 200 of occurring in any given year.

MTCBC as a LLFA has set the key flood risk indicator of people at risk of flood at a

threshold of 200(equivalent to 85 properties) to decide if a flood is of local significance. A flood event of this magnitude is at least one level of consequence down from the

national threshold but still represents a flood of considerable magnitude. Such a flood could occur as a very intense localised area such as a 1km square or cover the whole of the borough in a less intense rainfall event.

The data readily available has been analysed to give the number of properties flooded

in each incident and there are no records of flooding which affects 85 or more residential properties. And therefore no floods have been recorded as a result of this process.

4.2 Two floods have been identified as being locally significant within Merthyr Tydfil County

Borough Council. These have been identified from reports prepared following major floods. The two floods are:-

1 4th December 1960 2 26th December 1979

Both these flood events have been entered into the Preliminary Assessment Report Spreadsheet – Annex 1 – Past floods and extracts from the spreadsheet are given below.

4.3 Details of December 1960 Flood.

Information about this flood event has been taken from a report prepared by the Glamorgan River Board. Precise details of the areas flooded were not given and therefore no plan has been produced of this flood.

Table 3 – Details of the December 1960 Flood

Summary Description On 3 and 4 December 1960 serious flooding took place throughout MTCB Council and the whole of Wales. The flooding followed a period since June 1960, during which there were a record number of wet days. The ground was therefore super-saturated. During November 1960 263mm of rainfall was recorded at Dowlais, which is within the FRA, and 525mm at Brecon, which is 25 km north of the FRA. This was the highest monthly rainfall recorded since 1885. A further 132mm of rain was recorded at Brecon on 3 December 1960. The conditions in the Taff were the worse in living memory with water levels above the 1929 flood and had probably not been exceeded for over 100 years Human Health Consequences A total of 90 residential properties were flooded in addition to the following 1 Public house flooded; 2 shops flooded; 22 major roads or supporting walls damaged; 2 culverts damaged; 2 footbridges over the River Taff damaged; 1 gas main damaged; 1 water main damaged

4.4 Details of December 1979 Flood. Information about this flood event has been taken from a report prepared by the Robinson Jones Partnership Ltd. Details of the areas flooded are shown in Fig. 7 Areas Flooded during December 1979 Flood. Table 4 – Details of the December 1979 Flood Summary Description Following heavy rainfall on the 26th and 27th December 1979 flooding occurred over a wide area of Wales causing extensive damage. It is estimated from Welsh Water Authority records that, in Pentrebach and Troedyrhiw catchment areas, both of which are in the FRA, between 113mm and 140mm or rain fell. This storm was preceded by two other significant storms during the month of December. The first storm between 4th and 10th December caused rainfall of 175mm to be deposited on the Brecon Beacons. Records of the second storm between, 15th and 19th December, shows over 100mm of rainfall over the Brecon Beacons. As a result of these earlier storms the catchment was totally saturated prior to the storm on 26th and 27th December and significant parts of the upper catchments were frozen. These facts resulted in a 100% runoff causing higher flows than would normally be expected for a storm of this intensity. Human Health Consequences A total of 189 residential properties were flooded within 0.08323 km” In Pentrebach 43 houses, 1 Hotel and a cricket field flooded. In Troedyrhiw 146 houses flooded and a major culvert collapsed. In Rhydycar there were two fatalities as a result of a culvert collapse

5 Future Flood Risk

5.1 MTCBC has no information currently available relating to future flooding other than that provided by the EAW, as listed below. It is the intension of MTCBC to carry out electronic modelling within the Flood Risk Area as part of the preparation of Flood Hazard and Flood Risk Maps and the Flood Risk Management Plan for the borough.

5.2 The Environment Agency has produced two sets of flood maps giving an assessment

of flood risk for the whole of England and Wales. The first generation mapping referred to as Areas Susceptible to Surface Water Flooding (AStSWF) containing three levels of banding with a 1 in 200 chance of occurring. A second generation of maps have since been prepared and issued by the EAW referred to as the Flood Map for Surface Water (FMfSW). This revised model contains two flood events 1) 1 in 30 and 2) 1 in 200 annual chance of occurring. Each data set is further subdivided to give areas likely to flood to a depth greater than 0.1m and greater than 0.3m.

5.3 The EAW have carried out validation checks on the two mapping system and for the

type of terrain within MTCBC, which is mostly steeply sloping hillsides it is considered that the Flood Maps for Surface Water are the most appropriate to use for this PFRA. Fig. 8 MTCBC Flood Map for Surface Water 1 in 200 shows the flooding predicted by this model.

5.4 At this stage MTCBC does not have details of the capacity of the local drainage but this

information will be calculated as part of the preparation work for the Flood Hazard and Flood Risk Maps and the Flood Risk Management Plans.

5.5 Annex 2 of the Preliminary Flood Risk Assessment Spreadsheet has been completed

for a 1 in 200 year storm flooding to a depth greater than 0.3m. 5.6 As no other information is available the second generation of maps prepared and

issued by the EAW referred to as the Flood Map for Surface Water (FMfSW). Have been accepted as the locally agreed surface water information.

5.7 The impacts of climate change

The impact of climate change on local flood risk is relatively poorly understood. Several national flood maps have informed the preliminary assessment report - specifically the Flood Map for Surface Water (surface runoff), Areas Susceptible to Surface Water Flooding (surface runoff), Areas Susceptible to Groundwater Flooding (groundwater) and Flood Map (ordinary watercourses). These do not show the impact of climate change on local flood risk. There was consensus amongst climate model projections presented in the IPCC fourth assessment report for northern Europe suggesting that in winter high extremes of precipitation are very likely to increase in magnitude and frequency. These models project drier summers with increased chance of intense precipitation — intense heavy downpours interspersed with longer, relatively dry periods (Solomon et al., 2007).

5.8 UKCP09

United Kingdom Climate Projections 2009 (UKCP09) provides the most up to date projections of future climate for the UK (http://ukclimateprojections.defra.gov.uk/). In terms of precipitation, the key findings are: By the 2080s, under Medium emissions, over most of lowland UK

Central estimates are for heavy rain days (rainfall greater than 25 mm) to increase by a factor of between 2 and 3.5 in winter, and 1 to 2 in summer.

By the 2080s, under Medium emissions, across regions in England & Wales

The central estimate (50% probability) for winter mean precipitation % change ranges from +14 to +23

Central estimate for summer mean precipitation % change ranges from -18 to -24.

Certain key processes such as localised convective rainfall are not represented within this modelling so there is still considerable uncertainty about rarer extreme rainfall events for the UK. We can be more certain that heavy rainfall will intensify in winter compared to summer. The proportion of summertime rainfall falling as heavy downpours may increase. The impact of these changes on local flood risk is not yet known.

5.9 Appraisal guidance Current project appraisal guidance (Defra, 2006) provides indicative sensitivity ranges for peak rainfall intensity, for use on small catchments and urban/local drainage sites. These are due to be updated following the UKCP09 projections above. They describe the following changes in peak rainfall intensity; +5% (1990-2025), +10% (2025-2055), +20% (2055-2085) and +30% (2085-2115). This was reviewed by the Met Office in 2008 using UKCP09 models (Brown et al., 2008). They suggest that, on the basis of our current understanding, these levels represent a pragmatic but not a precautionary response to uncertainty in future climate impacts. In particular for a 1 in 5 year event, increases in precipitation intensity of 40% or more by the 2080s are plausible across the UK at the local scale.

5.10 Long term developments It is possible that long term developments might affect the occurrence and significance of flooding. However current planning policy aims to prevent new development from increasing flood risk. 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 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 without increasing flood risk elsewhere and where possible, reducing flood risk overall." 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." Adherence to Government policy ensures that new development does not increase local flood risk. However, in exceptional circumstances the Local Planning Authority may accept that flood risk can be increased contrary to Government policy, 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), but should be recorded here so that they can be reviewed in the future.

6 Review of indicative Flood Risk Areas 6.1 In order to ensure consistence of approach, Defra and WAG have identified a number

of key risk indicators and their thresholds to establish significant to determine the existence of indicative Flood Risk Areas.

6.2 The methodology is based on using the flood maps produced by the EAW to identify 1km squares where flood risk exceeds a defined threshold. These squares are known as Areas above Flood Risk Threshold (Blue Squares). The key flood risk indicators and their thresholds are as follows:-

1 a minimum of 200 people 2 a minimum of 20 businesses 3 2 or more critical services

The EAW has identified 20 blue squares within MTCBC which are Areas above the Flood Risk Threshold.

6.3 A cluster of these blue squares is an indication that an area of concentrated flood risk has been identified. Where there are four or more touching blue squares within a 3km x 3km square the whole 3km x 3km square has been considered as an area which could form part of an indicative Flood Risk Area. The key flood risk indicator for establishing an indicative Flood Risk Area is numbers of people at risk of being affected by flooding. If there is a minimum of 5,000 people within a series of connecting 3km x 3km grids, as identified above, then an indicative Flood Risk Area has been established.

6.4 On the basis of the 20 blue squares, 16 of which are within the indicative Flood Risk Area, and the methodology defined above, the EAW have identified an indicative Flood Risk Area within MTCBC of 45 km2. The blue squares and indicative Flood Risk Area identified by the EAW within MTCBC are shown on Fig. - 3 EAW Indicative Flood Risk Area and Blue Squares for MTCBC.

6.5 In order to review the indicative Flood Risk Area all 153 km squares within MTCBC were reviewed by studying each layer of information as listed in Table 2 – Data Collected. MTCBC is satisfied that all the squares which have been identified, by the EAW, as Areas above the Flood above Flood Risk Threshold have been correctly identified.

6.6 The Key Flood Risk Indicators for MTCBC have been calculated by the EAW as

follows:- Human health consequences –

Number of people (2.23 multiplier) 7,071 Other human health consequences –

Number of critical services flooded 25 Economic consequences – number of

non-residential properties flooded 806

See Appendix 1 – Flood Risk Area – Information for reporting on Flood Risk Area Data from EAW and MTCBC.

7 Identification of Flood Risk Areas

7.1 As part of the review carried out by MTCBC as noted above clause 6.5 two 1 km squares were identified as being Areas above the Flood Risk Threshold. They are X304Y207 and X307Y201.

7.2 Grid square X304Y207 has been made into a blue square by MTCBC because there

are 4 critical services which have been identified as being at risk of flooding as listed below

1 Goetre Infants School 2 Goetre Junior School 3 Cyfarthfa Junior School.

All three are shown as being subject to flooding on the EAW Flood Map for Surface Water 1 in 200 year event depth >0.30m.

4 St Aloysius RC Primary School

This school has a culverted ordinary watercourse flowing through its grounds. If the grid blocks, the culvert collapses or the flow of water is above the culvert capacity the school would flood.

As a result this square is defined as an Area above Flood Risk Threshold

As a result of making this square blue, and using the Defra/WAG methodology, 5 additional squares have been brought into the MTCBC Flood Risk Area. See Fig 3 MTCBC Flood Risk Area and Blue squares for MTCBC

7.3 Grid square X307Y201 has been made into a blue square by MTCBC because there are 3 critical services which have been identified as being at risk of flooding as listed below:-

1 Troedyrhiw Pumping Station - which pumps combined sewage from 61

residential properties 2 Haven Close which provides sheltered accommodation for vulnerable

people 3 Afon Taf high School.

All three critical services are shown as being subject to flooding on the EAW Flood Map for Surface Water 1 in 200 year event flooding > 0.30m deep. By making this square blue, and using the Defra/WAG methodology 6 additional squares have been brought into the MTCBC Flood Risk Area. See Fig 3 MTCBC Flood Risk Area and Blue squares for MTCBC.

7.4 As a result of the above amendment the EAW blue square X307Y199 becomes contiguous with the MTCBC Flood Risk Area and therefore we consider it appropriate that the Flood Risk Area should be increased to include this square. See Fig 3 MTCBC Flood Risk Area and Blue squares for MTCBC.

7.5 On the basis of the 22 blue squares identified by MTCBC, 20 of which are within the MTCBC Flood Risk Area, and the methodology defined above, MTCBC have identified an indicative Flood Risk Area of 58 km2..

See Fig 3 MTCBC Flood Risk Area and Blue squares for MTCBC.

7.6 The Key Flood Risk Indicators for the MTCBC Flood Risk Area have been calculated by the as follows:-

Human health consequences - Number of people (2.23 multiplier)

Other human health consequences - Number of critical services flooded

Economic consequences - number of non-residential properties flooded

See Appendix 1 - Flood Risk Area - Information for reporting on Flood Risk Area Data from EAW and MTCBC.

Next steps

8.1 In order to continue to fulfil the role as Local Lead Flood Authority, Merthyr Tydfil CB Council are required to investigate future flood events and ensure continued collection, assessment and storage of flood risk data.

It is essential that all new records of flood events are documented in accordance with the INSPIRE Directive (2007lUEC). The format of the records will be compatible between departments sections within MTCBC and will also be in an electronic format suitable for importation to our GIs system.

8.2 A preliminary report has been submitted to the Scrutiny Committee of MTCBC. The committee has decided that no further submission will be necessary before the Preliminary Flood Risk assessment report is submitted to the Environment Agency. Prior to the report being sent to the EAW it will be thoroughly reviewed within the Engineering Department.

8.3 Under the Flood Risk Regulations the Environment Agency has been given a role of reviewing, collating and publishing all PFRAs.

The EAW will undertake a technical review of the PFRA which will focus on instances where Flood Risk Areas have been amended and ensure the format of these areas meets the appropriate standards. The PFRAs will finally be signed off by the Environment Agency Regional Director before they are signed off, collated, published and submitted to the European Commission.

8.4 Following the submission of the PFRA by MTCBC, which must be completed by 22nd June 2011, work will commence on the flood Hazard and Flood Risk Maps, to be completed by 22" June 2013 and finally the Flood Risk Management Plansto be finalised by 22"d June 201 5.

Once this cycle has been completed the review procedure will commence which will result in a more detailed Flood Risk assessment report being submitted to the European Commission by 22" December 2017.

References

Flood and Water management Act 2010 http://www.leaislation.aov.uWuk~~1a/2010/29/contents

The Flood Risk Regulations httr>://www. leaislation.aov.uk~sksi/2009/304Ucontents/made

Preliminary Flood Risk assessment (PFRA) Final Guidance Report -GEHOl21 OBTGH-E-E Environment Agency http://~ublications.environment-aaencv.cw.uk/

Preliminary Flood Risk Assessment (PFRA) Annexes to the final guidance Report - GEH01210BTHF-E-E Environment Agency http://~ublications.environment-aaencv.aov.uk/

Selecting and Reviewing Flood Risk Areas for local sources of flooding Guidance to Lead Local Flood Authorities Flood Risk Regulations 2009 Defra / Welsh assembly Government http://ww2.defra.gov.uWenvironment/flooding/

Annexes

Annex I - Records of past floods and their significant consequences (preliminary assessment report spreadsheet)

Refer to Annex 1 of the Preliminary Assessment Spreadsheet

Annex 2 - Records of future floods and their consequences (preliminary assessment report spreadsheet)

Refer to Annex 2 of the Preliminary Assessment Spreadsheet

Annex 3 - Records of Flood Risk Areas and their rationale (preliminary assessment report spreadsheet)

Refer to Annex 3 of the Preliminary Assessment Spreadsheet

Annex 4 - Review checklist

Refer to Annex 4 of the Preliminary Assessment Spreadsheet

Annex 5 - GIs layer of flood risk area

GIs layer sent separately to the Environment Agency

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Appendix I - lnformation for Reporting on Flood Risk Area EAW and MTCBC

Grid Reference Human health consequences -

residential properties

Indication Flood Risk Area - Information Provided by the Environment Agency

Human health consequences -

Number of people (2.34 multiplier)

SO0592205878 30221 7071 I~etai led GIs

Property count method

25 1 806I~etailed GIs Areas added to Indicative Flood Risk Area by MTCBC Areas added by making square X304Y207 into a Blue square

Economic consequences - number of non-

residential properties

flooded

Other human health

consequences - Number of

critical services flooded

Property count method

X303Y209 X302Y208 - - X302Y207 X302Y206 X302Y205 Additional Count

0 1 9

17 0

27

0 2

21 40

0 63

Areas added by making square X307Y201 into a Blue square

Estimated from map Estimated from map Estimated from map Estimated from map Estimated from map

X308Y203 X308Y202 X308Y201 X308Y200 X307Y 199 X306Y200 X305Y200 Additional Count

1 0 0 0 0 1

0 0

21 0

152 12 0

185 EA Blue Square added to Flood Risk Area

0 0 0 0 0 0

0 0

49 0

356 28

0 433

X307Y199 TOTALS FOR FLOOD RISK AREA

Estimated from map Estimated from map Estimated from map Estimated from map Estimated from map

Estimated from map Estimated from map Estimated from map Estimated from map Detailed GIs Estimated from map Estimated from map

152 3386

0 0 0 0 0 0 0 0

356 7923

0 0 0 0 6 0 0 6

Detailed GIs

Estimated from map Estimated from map Estimated from map Estimated from map Detailed GIs Estimated from map Estimated from map

0 26

6 81 8

Detailed GIs