River Dee Catchment Flood Management Plan Summary Report January 2010 Managing Flood Risk We Are Environment Agency Wales

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River Dee Catchment Flood Management Plan Summary Report January 2010 managing flood risk We are Environment Agency Wales. It’s our job to look after your environment and make it a better place – for you, and for future generations. Your environment is the air you breathe, the water you drink and the ground you walk on. Working with business, Government and society as a whole, we are making your environment cleaner and healthier. Environment Agency Wales. Out there, making your environment a better place.

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Environment Agency Wales Cambria House 29 Newport Road Cardiff CF24 0TP Tel: 0870 8506506 Email: [email protected] www.environment-agency.gov.uk

Front cover image: River Dee at Llangollen © iStockphoto.com/BackyardProduction Introduction

I am pleased to introduce our summary of the River Dee Catchment Flood Management Plan (CFMP). This CFMP gives an overview of the flood risk in the River Dee catchment and sets out our preferred plan for sustainable flood risk management over the next 50 to 100 years.

The River Dee CFMP is one of 77 CFMPs for England such as the tidal area of the river and much of the river and Wales. Through the CFMPs, we have assessed corridor between Bangor-on-Dee and Chester, defences inland flood risk across all of England and Wales for are critical to protecting communities from flooding. the first time. The CFMP considers all types of inland The highest risk areas now and in the future, are those flooding, from rivers, groundwater, surface water affected by tidally influenced flooding, for example the and tidal flooding, but not flooding directly from the Deeside and Sealand conurbations and Chester. sea (coastal flooding), which is covered by Shoreline Management Plans (SMPs). Our coverage of surface We have worked with others to produce this CFMP, and groundwater is however limited due to a lack of including: local authorities, water companies, available information. environmental groups, land owners and land managers. Whilst there is broad support for this plan, The role of CFMPs is to establish flood risk management local authorities have raised concerns about limited policies which will deliver sustainable flood risk resources, prioritisation and the potential impact on management for the long term. This is essential if we current development and regeneration proposals. Also, are to make the right investment decisions for the future land managers have raised concerns about how flood and to help prepare ourselves effectively for the impact risk is managed in rural areas. We cannot reduce flood of climate change. We will use CFMPs to help us target risk on our own. We will therefore work closely with all our limited resources where the risks are greatest. our partners to improve the co-ordination of flood risk activities and agree the most effective way to manage This CFMP identifies flood risk management policies to flood risk in the future. assist all key decision makers in the catchment. It was produced through a wide consultation and appraisal This is a summary of the main CFMP document. If you process. However it is only the first step towards an need to see the full document, an electronic version integrated approach to Flood Risk Management. As we may be obtained by emailing enquiries@environment- all work together to achieve our objectives, we must agency.gov.uk. monitor and listen to each others progress, discuss what has been achieved and consider where we may need to review parts of the CFMP.

The River Dee catchment has a history of flooding and flood risk. Management of flood risk in the catchment is undertaken through various means including regulation Chris Mills of the headwaters at Llyn Tegid. For some localities, Director Wales

Environment Agency Wales River Dee Catchment Flood Management Plan 1 Contents

The purpose of a CFMP in managing flood risk 3 Sub-areas 1 Upper Dee 14 Catchment overview 4 2 Main Alyn 15 Current and future flood risk 6 3 Middle Dee 16 4 Wrexham 17 Future direction for flood risk management 12 5 Lower Dee 18 6 Deeside, Wirral and North Flintshire 19 7 Chester 20 8 Mold 21 9 Bangor-on-Dee 22 10 Bala 23

Map of CFMP policies 24

Image: Dee northern embankment on the tidal River Dee

2 Environment Agency Wales River Dee Catchment Flood Management Plan The purpose of a CFMP in managing flood risk

CFMPs help us to understand the • internal drainage boards, water CFMPs aim to promote more scale and extent of flooding now companies and other utility sustainable approaches to and in the future, and set policies companies to help plan their managing flood risk. for managing flood risk within the activities in the wider context catchments. CFMPs should be used of the catchment; The policies identified in the to inform planning and decision CFMP will be delivered through making by key partners such as: • transportation planners; who a combination of different can use the plan to inform approaches. • the Environment Agency, who will their activities; use the plan to guide decisions Together with our partners, we on investment in further plans, • land owners, farmers and land will implement these approaches projects and actions; managers who manage and operate through a range of delivery plans, land for agriculture, conservation projects and actions. • local authorities, who can use and amenity purposes; the plan to inform spatial The relationship between the CFMP, planning activities and • the public and businesses to delivery plans, strategies, projects emergency planning; enhance their understanding and actions is shown in Figure 1. of flood risk and how it will be managed.

Figure 1. The relationship between CFMPs, delivery plans, projects and actions

Policy planning • CFMPs and SMPs. • Action plans define requirement for delivery plans, projects and actions.

Policy delivery plans (see note) Projects and actions • Influence spatial planning to reduce risk • Make sure our spending delivers the best and restore floodplains. possible outcomes. • Prepare for and manage floods • Focus on risk based targets, for example (including local Flood Warning plans). numbers of households at risk. • Managing assets. • Water level management plans.

• Land management and habitat creation. Note: Some plans may not be led by us – we may identify the need and encourage their development.

Environment Agency Wales River Dee Catchment Flood Management Plan 3 Catchment overview

The River Dee is 110 kilometres long and flood defences, which are still The upland catchment is from its source in the Snowdonia maintained today, were constructed predominantly rural, with sheep National Park to where its estuary to protect land from tidal inundation. farming on the poorer areas of discharges into Liverpool Bay. The River Dee is normally tidal up grassland and significant areas Upstream of Llyn Tegid the river to Chester Weir. This boundary is of commercial forestry. There is is fast flowing in a narrow incised exceeded for spring high tides and intensive dairy farming on the valley, whilst downstream of the extreme tides when tidal influence fertile lowlands in and around lake the valley bottom and natural can affect river levels as far upstream Wrexham and on the Cheshire floodplain opens out to approximately as Shocklach, 15 kilometres Plain, and arable farming in Wirral one kilometre wide. The river once upstream of Chester Weir. and Sealand. Only six per cent again follows a narrow incised valley of the catchment is urban with The natural river system is modified through Llangollen and downstream Wrexham, Chester, and Deeside in the upper catchment through flow to Erbistock (upstream of Bangor-on- (the conurbation embracing control at the Bala sluices located at Dee). Between Erbistock and Chester Connah’s Quay, Queensferry, the confluence of the River Dee and the floodplain is flat and very wide. Pentre, Sandcroft, Hawarden the River Tryweryn. The extensive Map 1 shows the location and extent Airport, and Saltney) being the section of natural river meanders of the CFMP area. main urban centres accounting for below Bangor-on-Dee is one of the over 60 per cent of the population. Downstream of Chester Weir the river best examples of such features in Tourism, cottage industries, retail, was canalised over 200 years ago England and Wales. commercial and industrial activities in and around Chester, Wrexham, Deeside and the smaller towns are very important to the economy of “One of the greatest challenges now this area. and in the future will be to manage The catchment is rich in biodiversity in terms of species and habitats. the consequences of flooding from Approximately 16 per cent of the catchment is designated for its the tidally influenced River Dee.” nature conservation value. The River Dee is designated as a site of special scientific interest (SSSI) and Llyn Tegid is a Ramsar site. The Dee Estuary has Special Protection Area (SPA), Special Area of Conservation (SAC) and Ramsar designations. Parts of the Clwydian Mountain Range are designated as an Area of Outstanding Natural Beauty (AONB). In all, 18 per cent of the catchment is within the Snowdonia National Park or has AONB designation.

Lower River Dee floodplain on the Cheshire Plain

4 Environment Agency Wales River Dee Catchment Flood Management Plan Map 1. Location and extent of the River Dee CFMP area

Environment Agency Wales River Dee Catchment Flood Management Plan 5 Current and future flood risk

Overview of the current areas, which had no record of re-occurrence of this flooding flood risk flooding in living memory, were in these localities; affected on this occasion. • groundwater flooding has Flood risk is the combination of The sources of flood risk are: occurred in some areas and two components; the likelihood caused road flooding and some (or probability) of a particular • river flooding occurs fairly property flooding. These are flood event occurring and the frequently in the upper localised issues and groundwater consequence (or impact) that catchments of the River Dee, flood risk is considered to be the flood event would have if River Alwen and River Alyn. low at a catchment scale. it occurred. In the remainder of the River Dee catchment, floodplains The probability of a flood event are generally wider, with is the likelihood of a flood of that What is at risk? flooding affecting large areas size occurring within a one year of agricultural land and urban CFMPs assess how flood risk is likely period. It is described as an annual areas such as Wrexham, Mold, to change in the next 100 years. They exceedance probability (AEP) and Chester, and the Deeside and do this at a strategic level and not at is expressed as a percentage. Sealand communities; a detailed, local level. For example, a 1% AEP flood event has a one per cent chance • tidally influenced river flooding We used computer models to or 0.01 probability of occurring can occur when extreme tidal simulate river flows and produce in any one year. events coincide with high indicative numbers of properties, river flows. This affects all infrastructure and environmental Unless otherwise stated, numbers communities close to the river features at risk. These models take in this report are based on the 1% as far upstream as Shocklach in to account the benefit of current AEP river flood event. More extreme Green. Tide locked outfalls flood defences. Where applicable, events can occur at any time. The affect locations in Deeside, tidal influences on river flows have likelihood of an extreme event Chester and Flint; also been modelled. Where models occurring is small, although the are not available we have based our consequences are potentially • surface water flooding is flood risk estimates on our Flood very serious, particularly where extensive in the Lower Dee Maps, which do not include flood defences could be overtopped. (Mold and Wrexham) and defences. Numbers produced are Dee Estuary sub-catchments Flooding has occurred at many sufficient for the purposes of the (Deeside, Sealand and Chester), locations throughout the River Dee CFMP only. and also in the lower reaches of CFMP area, mostly from the main the River Alyn catchment near the It is estimated that a 1% AEP flood River Dee and its major tributaries, confluence with the River Dee; event could affect approximately but also from smaller watercourses. 4,200 properties across the CFMP. Significant floods were recorded in • sewer flooding has occurred 1890, 1946, and 1964 and recently in Chester, Flint, Deeside, There are 13 internationally in 2000. Mold, Coedpoeth and designated sites and 30 SSSIs at Rhosllannerchrugog. This risk from the 1% AEP flood event During Autumn 2000, exceptional information is based on and 22 scheduled monuments. rainfall caused widespread flooding historical incidents and does Depending on the nature of the throughout the catchment. Many not necessarily indicate likely environmental feature, flooding

6 Environment Agency Wales River Dee Catchment Flood Management Plan may have a negative or positive Table 1. Key locations currently at risk in a 1% AEP flood event impact. For example, flooding may create or enhance a habitat Number of properties at risk Locations in some areas e.g. a new flood > 1,000 None storage wetland, or have the potential to cause physical damage to the historic environment e.g. 500 to 1,000 Chester, Deeside listed buildings and scheduled monuments. 100 to 500 Bala, Bangor-on-Dee, Whitchurch, Wrexham, Mold, Flint, Holywell

Where is the risk? 50 to 100 Cefn Mawr Area, New Broughton, Sealand To assess flood risk at a strategic level we have identified a number 25 to 50 None of key locations where we have carried out a more detailed analysis of flood risk. These are presented in Table 1 and Map 2. This is not an exhaustive list of locations. Flood Table 2. Infrastructure currently at risk in a 1% AEP flood event risk in all other areas has been 30 electricity/gas plants considered in the development of the CFMP. 17 sewage/water treatment plants The highest number of properties currently at risk from a 1% AEP flood 3 telephone exchanges event are located within Chester and Deeside. The areas which 12 schools are classed as the most socially vulnerable to flooding are located 2 railway stations in Bala, Cefn Mawr, Whitchurch, Mold and Chester. 25 kilometres of ‘A’ roads

We recognise there is potential 13 kilometres of rail track risk from localised surface water and groundwater flooding in other areas of the CFMP, however there is limited information currently available.

Table 2 lists some of the infrastructure currently at risk in the CFMP area.

Environment Agency Wales River Dee Catchment Flood Management Plan 7 Map 2. Number of properties currently at risk in a 1% AEP flood event

How we currently manage the risk in the catchment

We can split the work we do to management of the consequences • encouraging land use planning manage flood risk into two types: of flooding. This will include: to take account of flood risk in determining the location, layout • work which helps us to reduce • promoting awareness of and design of new development; the likelihood of a flood flooding so that organisations, occurring, and communities and individuals are • flood proofing properties and aware of the risk and are better infrastructure to improve the • work which helps us to deal with prepared to take action in time resilience (reducing the damage the consequences of flooding. of flood; from flood water) and the In the past, we have focussed on resistance (keeping water out) • providing flood warning services to avoid harm. reducing the likelihood of flooding to those at risk, to enable them by building flood defences. Other to take action; In this CFMP area, current flood risk measures have been used but not management is mainly reliant on as a primary solution to flood risk. • improved incident and flood warning, development control It is now widely recognised that emergency response by the and local defences at communities, managing flood risk to provide emergency services and by such as Bangor-on-Dee. More safe and sustainable communities those at risk from flooding; extensive defences are dominant will require more emphasis on the in the tidal Dee Estuary.

8 Environment Agency Wales River Dee Catchment Flood Management Plan Some of the ways in which we • asset management and At present we forecast river currently manage risk in the maintenance (managing levels on the main River Dee catchment include: current risk); based on observed conditions. Flood forecasting models are in • flood risk mapping and data We build, operate and maintain flood defences in the CFMP area. development for the main River management (understanding Dee. Recent improvements to the risks now and in the future); We own and manage the sluice and flow control arrangements the flood forecasting model Flood risk mapping is at Llyn Tegid reservoir. In the on the River Alyn are being fundamental to understanding upper and middle catchments developed and will be flood risk and managing it flood defences generally protect implemented in the future. effectively. agricultural land with local In the River Dee catchment there A number of flood risk mapping schemes, including defences is a well developed flood warning studies have recently been at Bala, the recently completed service providing flood warnings undertaken in order to better schemes at Rhydymwyn and to 540 properties. understand flood risk and Rossett, and the Trevalyn improve the quality of our Flood and Bangor-on-Dee schemes • flood incident management Maps. We have recently been protecting urban communities. (responding to flooding events); improving our Flood Maps in the Emergency response to flood tidal Dee area and the River • flood forecasting and warning events is mainly co-ordinated Alyn catchment. (flood event management); through Civil Contingency We use the latest technology arrangements and Local • strategic planning and to monitor rainfall, river levels, Resilience Forums. development control (managing tides and sea conditions and Our role is to advise our partners future risk and adapting to use this information to produce climate change); through these arrangements. flood warnings. We support and participate in CFMPs and SMPs are an emergency response exercises. important part of strategic planning allowing us to look at a range of strategic measures. These include looking for opportunities to reduce run- off through better rural land management and restoration of floodplains through redevelopment of properties and infrastructure. We work with local authorities to ensure their local development plans address flood risk. We have worked with Denbighshire County Council and helped them produce a Strategic Flood Consequence Assessment to support their local development plan.

Horseshoe Falls on the River Dee near Llangollen

Environment Agency Wales River Dee Catchment Flood Management Plan 9 The impact of climate change and future flood risk

Future flood risk will be influenced • small changes to land Future increase in flood risk in the by climate change, changes in management and agricultural River Dee CFMP tends to be largest land use (for example urban practices throughout the in towns located near the mouth of development) and rural land majority of the catchment and rivers, or where the tidal influence management. Sensitivity testing larger changes (agricultural travels inland up an estuary. This is identified that the main driver of intensification and improved where the effects of sea level rise change to future flood risk is climate drainage) in the Cheshire Plain. and increased river flows combine, change. Urban development and resulting in more frequent, deeper Assuming the current level of flood changes to land management have and more extensive flooding. risk management continues, we much less impact on flood risk at estimate that by 2100 the number Locations where this is likely the catchment-wide scale and are of properties at risk from the 1% to occur include the Deeside also unlikely to occur at the AEP flood event will increase, from conurbation, Sealand and Chester. whole catchment scale. approximately 4,200 to around In Bala and Bangor-on-Dee the The following scenario was used 6,400, unless actions are taken to numbers of properties potentially at to analyse future flood risk: manage the increasing risks. risk are already high and flood risk is predicted to increase. Localities • 20 per cent increase in flows; Figure 2 shows the difference such as Mold, Wrexham, Whitchurch between current and future flood • a total sea level rise of one metre and some other communities would risks from a 1% AEP flood event, by the year 2100; experience flooding from more assuming current management frequent, less severe flood events. activities. The most significant • urban development increases in Locations at greatest risk in the increases in future risk occur in the urban areas of Wrexham, the future are shown in Table 3. Deeside conurbation and Chester; Chester, Deeside and Mold.

Figure 2. Current and future (2100) numbers of properties at risk from a 1% AEP flood event

2000

1800

1600

1400

1200

1000

800

600

400

200

0 Bala Bangor-on- Cefn Mawr Chester Deeside Flint Holywell Llangollen Mold New Sealand Whitchurch Wrexham Dee Area Broughton

Current Future

10 Environment Agency Wales River Dee Catchment Flood Management Plan Wetter winters and more Table 3. Key locations at risk in a future (2100) 1% AEP flood event severe storm events are likely to lead to increased surface Number of properties at risk Locations water. This may be of particular > 1,000 Chester concern in communities such as Wrexham, the Deeside conurbation, Chester, Buckley 500 to 1,000 Bala, Mold, Deeside and Rhosllanerchrugog and to a lesser extent in Mold, Flint, 100 to 500 Cefn Mawr Area, Bangor-on-Dee, Holywell and Neston where such Whitchurch, Wrexham, Sealand, flooding is already an issue. Flint, Holywell

In the future, we do not expect 50 to 100 New Broughton the area of environmental and landscape designations at risk 25 to 50 Llangollen of flooding to increase significantly and we do not expect new sites to be flooded.

We expect surface water and Table 4. Infrastructure at risk in the future (2100) 1% AEP flood event groundwater flooding will increase. Organisations will 48 electricity/gas plants need to work together to investigate and manage this 18 sewage/water treatment plants flood risk in the future. 4 telephone exchanges Potential increase in infrastructure at risk of flooding 14 schools in the future is shown in Table 4. One of the most notable 6 railway stations increases is the number of electricity/gas installations, 33 kilometres of ‘A’ roads from 30 in the present to 48 in the future. The distance of 18 kilometres of rail track combined road and rail affected by flooding also potentially increases from 38 kilometres to 51 kilometres. Increases in infrastructure affected are greatest around the River Dee estuary and in particular in Chester and the Deeside conurbation.

The lower River Dee floodplain

Environment Agency Wales River Dee Catchment Flood Management Plan 11 Future direction for flood risk management

Approaches in each sub-area

We have divided the River Dee catchment into 10 distinct sub-areas which have similar physical characteristics, sources of flooding and level of risk. We have identified the most appropriate approach to managing flood risk for each of the sub-areas and allocated one of six generic flood risk management policies. These are shown in Map 3 and Table 5.

To select the most appropriate policy, the plan has considered how social, economic and environmental objectives are affected by flood risk management activities under each policy option. Policy analysis and selection is based on flood risk across the entire CFMP area and not just the key locations referred to earlier.

Map 3. Sub-areas in the River Dee CFMP

12 Environment Agency Wales River Dee Catchment Flood Management Plan Table 5. Policy options ➜ Policy 1 Areas of little or no flood risk where we will continue to monitor and advise This policy will tend to be applied in those areas where there are very few properties at risk of flooding. It reflects a commitment to work with the natural flood processes as far as possible.

➜ Policy 2 Areas of low to moderate flood risk where we can generally reduce existing flood risk management actions This policy will tend to be applied where the overall level of risk to people and property is low to moderate. It may no longer be value for money to focus on continuing current levels of maintenance of existing defences if we can use resources to reduce risk where there are more people at higher risk. We would therefore review the flood risk management actions being taken so that they are proportionate to the level of risk.

➜ Policy 3 Areas of low to moderate flood risk where we are generally managing existing flood risk effectively This policy will tend to be applied where the risks are currently appropriately managed and where the risk of flooding is not expected to increase significantly in the future. However, we keep our approach under review, looking for improvements and responding to new challenges or information as they emerge. We may review our approach to managing flood defences and other flood risk management actions, to ensure that we are managing efficiently and taking the best approach to managing flood risk in the longer term.

➜ Policy 4 Areas of low, moderate or high flood risk where we are already managing the flood risk effectively but where we may need to take further actions to keep pace with climate change This policy will tend to be applied where the risks are currently deemed to be appropriately-managed, but where the risk of flooding is expected to significantly rise in the future. In this case we would need to do more in the future to contain what would otherwise be increasing risk. Taking further action to reduce risk will require further appraisal to assess whether there are socially and environmentally sustainable, technically viable and economically justified options.

➜ Policy 5 Areas of moderate to high flood risk where we can generally take further action to reduce flood risk This policy will tend to be applied to those areas where the case for further action to reduce flood risk is most compelling, for example where there are many people at high risk, or where changes in the environment have already increased risk. Taking further action to reduce risk will require additional appraisal to assess whether there are socially and environmentally sustainable, technically viable and economically justified options.

➜ Policy 6 Areas of low to moderate flood risk where we will take action with others to store water or manage run-off in locations that provide overall flood risk reduction or environmental benefits This policy will tend to be applied where there may be opportunities in some locations to reduce flood risk locally or more widely in a catchment by storing water or managing run-off. The policy has been applied to an area (where the potential to apply the policy exists), but would only be implemented in specific locations within the area, after more detailed appraisal and consultation.

Environment Agency Wales River Dee Catchment Flood Management Plan 13 Sub-area 1

Upper Dee

Our key partners are: Flooding on the River Dee Actions to implement downstream of Llyn Tegid is Local Authorities and communities part managed through the Bala the policy include: flow control sluices. Raised Landowners and managers Review and rationalise our defences protect Llanuwchlyn current actions to ensure they Snowdonia National Park Authority and communities between are appropriate and targeted to Llanderfel and Corwen. locations of greatest risk. Countryside Council for Wales (CCW) Encourage and support our The vision and partners to produce local long preferred policy term plans to manage all sources The issues in this of flooding, particularly at sub-area Policy Option 3 – areas of low to Llanuwchlyn and communities moderate flood risk where we are between Llanderfel and Corwen. This is a rural area which includes generally managing existing flood These plans should include an the source of the River Dee in the risk effectively. assessment of the consequences Snowdonia National Park to its of flooding, including from confluence with the River Ceiriog Our vision is to ensure our actions overtopping of defences and between Llangollen and Erbistock. are appropriate and proportionate actions to manage these. They to the risks, now and in the future. Approximately 300 properties are should consider future options and currently at risk from the 1% AEP We will continue to control flood investment needs for defences, flood event, rising to around 450 water flows at Bala, whilst it is emergency planning and response, properties in the future. Current justifiable to do so. We will continue and development control issues. flood risk mainly affects isolated to maintain our defences, but it may Engage and advise the local and small groups of properties not be justifiable to increase their community to encourage people and agricultural land. Flooding is height in the future. Our vision at risk to take action to help generally from river and surface also includes: themselves. water sources. International and nationally designated • increased emphasis on actions Review the flow control and storage environmental sites are also to manage the consequences regime for reservoirs in view of the affected by flooding. of flooding; potential impacts of climate change.

• increased community and Develop an improved upper Dee individual awareness of their catchment model to improve our flood risks and adoption of understanding of flood risk. actions both can take to help themselves. Implement a flood forecasting model for the River Dee as a whole.

Encourage and support opportunities for land use and management change, which assist in achieving flood risk and wider benefits.

Upland River Dee Catchment

14 Environment Agency Wales River Dee Catchment Flood Management Plan Sub-area 2

Main Alyn

Our key partners are: The main communities are Actions to implement protected against flooding from the Local Authorities and communities River Alyn by schemes implemented the policy include: since the 2000 floods. Landowners and managers Review and rationalise our current actions to ensure they International and nationally D∑r Cymru Welsh Water are appropriate and targeted to designated environmental sites, locations of greatest risk. CCW including Alyn Valley Woods SAC are affected by flooding. Carry out a modelling study on the River Alyn to better understand the flood risk. The issues in this The vision and sub-area preferred policy Encourage and support our partners to produce local long term plans This is a mainly rural area, Policy Option 3 – areas of low to to manage all sources of flooding, particularly upstream of Mold. It moderate flood risk where we are particularly for communities includes the majority of the River generally managing existing flood downstream of Mold. These plans Alyn valley, from its source to the risk effectively. should include an assessment confluence with the River Dee. of the consequences of flooding, Our vision is to ensure our actions It includes the communities of including from overtopping of are appropriate and proportionate Gresford, Llay, Caergwrle and Hope defences and actions to manage to the risks, now and in the future. but excludes Mold and Rhydymwyn these. They should consider future which are in sub-area 8. We will continue to maintain options and investment needs our defences, but it may not be for defences, emergency planning Approximately 200 properties are justifiable to increase their height in and response, and development currently at risk from the 1% AEP the future. Our vision also includes: control issues. flood event, rising to around 290 properties in the future. The main • increased emphasis on actions Engage and advise the local source of flooding is the River Alyn, to manage the consequences community, to encourage people but there are also areas of local of flooding; at risk to take action to help surface water and sewer flooding. themselves. • increased community and Main roads and other infrastructure individual awareness of their flood are also at risk of flooding. Encourage and support studies by risks and adoption of actions both partners to identify surface water can take to help themselves. and sewer flooding issues and management options.

Support opportunities to store water or manage run-off to provide flood risk and environmental benefits.

Encourage and support opportunities for land use and management change, which assist in achieving flood risk and wider benefits. River Alyn weir at Caergwrle

Environment Agency Wales River Dee Catchment Flood Management Plan 15 Sub-area 3

Middle Dee

Our key partners are: The vision and Actions to implement the

Local Authorities and communities preferred policy policy include:

Landowners and managers Policy Option 2 – areas of low to Work with partners to determine moderate flood risk where we can how the policy of reducing actions is D∑r Cymru Welsh Water generally reduce existing flood risk most appropriately communicated management actions. and implemented. CCW Our vision is to reduce reliance and Investigate with local communities expenditure on the agricultural and land managers the feasibility of defences over time. We will follow changing management approaches The issues in this a risk based approach to rationalise for agricultural land, defences and sub-area our current activities and target our land drainage pumping stations. actions and limited resources to This area covers the River Dee locations of greatest risk. Develop flood resilience and catchment from its confluence with climate change adaptation plans the River Ceiriog to downstream We will continue to maintain for pumping station assets. of the confluence with the our defences, but it may not be River Clywedog. It includes justifiable to continue to maintain Encourage and support our the communities of Overton, these, or to increase their height in partners to produce local long term Whitchurch, Tattenhall and Malpas. the future. Our vision also includes: plans to manage all sources of flooding, particularly for Erbistock, Approximately 220 properties are • increased emphasis on actions Worthenbury, Malpas. These plans currently at risk from a 1% AEP flood to manage the consequences should include an assessment event, rising to around 310 in the of flooding; of the consequences of flooding, future. The main source of flooding including from overtopping of is the River Dee, but there are local • increased community and defences and actions to manage areas of surface water and sewer individual awareness of their these. They should consider future flooding, for example in Whitchurch flood risks and adoption of options and investment needs for and Tattenhall. actions both can take to defences, emergency planning help themselves. and response, and development Main roads, infrastructure, control issues. international and nationally designated environmental sites, Develop an updated catchment including the Dee Meanders SAC model, to include main tributaries are affected by flooding. in the middle Dee including Worthenbury Brook, River Clywedog Raised defences at Worthenbury and River Gwenfro. reduce the likelihood of flooding from Wych and Emral Brooks. Raised Engage and advise the local defences downstream of Bangor- community, to encourage people on-Dee, reduce the likelihood of at risk to take action to help flooding to agricultural land and themselves. buildings from the River Dee. Land drainage pumping stations in Worthenbury Meadows evacuate flood waters from this area. Middle Dee floodplain

16 Environment Agency Wales River Dee Catchment Flood Management Plan Sub-area 4

Wrexham

Our key partners are: Many urban locations within Actions to implement Wrexham and outlying towns Wrexham County Borough Council experience flooding from surface the policy include: water run-off and local sewer Local communities Encourage and support our partners systems. This affects property to produce local long term plans D∑r Cymru Welsh Water and roads. to manage all sources of flooding at Wrexham. These plans should Emergency services There are localised defences and include an assessment of the engineered river walls on the River consequences of flooding, including Gwenfro, through Wrexham and from overtopping of defences, and New Broughton, and on the River actions to manage these. They The issues in this Clywedog south of Wrexham. should consider future options and sub-area Wrexham is identified for residential, investment needs for defences, commercial and industrial growth in emergency planning and response, Mainly an urban area which the North East Wales/West Cheshire and development control issues to includes Wrexham and outlying Sub Regional Strategy. communities. The River Gwenfro avoid inappropriate development in flows from west to east through the high risk areas. centre of the town and joins the The vision and Seek to reduce the flow capacity River Clywedog to the south east restrictions and sources of of Wrexham. preferred policy blockages over time. Policy Option 4 – areas of low, Approximately 250 properties are moderate or high flood risk where Include the Rivers Clywedog and currently at risk of flooding from a we are already managing the flood Gwenfro in the River Dee, flood 1% AEP flood event, increasing to risk effectively but where we may risk mapping, catchment model to around 290 in the future. need to take further actions to keep better understand the risks. The main source of flooding to pace with climate change. Encourage and support studies by Wrexham town centre is the River Our vision includes improved partners to identify surface water Gwenfro. Locations to the south integration of actions by all parties and sewer flooding issues and west of the town, such as Five Fords to manage all sources of flood risk. management options, particularly and Bowling Brook experience in Wrexham town centre area and flooding from the River Clywedog. We will continue to maintain New Broughton. our defences, but it may not be justifiable to increase their height in Engage and advise the local the future. Our vision also includes: community, to encourage people at risk to take action to help • increased emphasis on actions themselves. to manage the consequences of flooding;

• increased community and individual awareness of their flood risks and adoption of actions both can take to help themselves. Wrexham

Environment Agency Wales River Dee Catchment Flood Management Plan 17 Sub-area 5

Lower Dee

Our key partners are: The vision and Actions to implement

Local Authorities and communities preferred policy the policy include:

Landowners and managers Policy Option 3 – areas of low to Review and rationalise our moderate flood risk where we are current actions to ensure they CCW generally managing existing flood are appropriate and targeted to risk effectively. locations of greatest risk.

Our vision is to ensure our actions Investigate with local communities The issues in this are appropriate and proportionate and land managers the feasibility sub-area to the risks, now and in the future. of changing management approaches for agricultural land, This is mainly a rural area We will continue to maintain defences and land drainage downstream of Worthenbury. our defences, but it may not be pumping stations. It contains much of the Dee justifiable to increase their height in Meanders, and several settlements the future. Our vision also includes: Encourage and support our partners to produce local long including Holt, Farndon, Rossett, • increased emphasis on actions Aldford and Eccleston. term plans to manage all sources to manage the consequences of flooding, particularly at Holt, Approximately 50 properties are of flooding; Rossett, Aldford, Eccleston, currently at risk of flooding from • increased community and Almere Shocklach and Farndon. a 1% AEP flood event, increasing individual awareness of their These plans should include an to around 70 in the future. The flood risks and adoption of assessment of the consequences main source of flooding is the River actions they can take to of flooding, including from Dee, but there are communities help themselves. overtopping of defences, and that experience flooding from actions to manage these. They local watercourses and drainage should consider future options systems, for example, Holt, and investment needs for Farndon and Eccleston. defences, emergency planning and response, and development Infrastructure and international control issues to avoid and nationally designated inappropriate development in environmental sites, including the high risk areas. Dee Meanders, are at flood risk. Engage and advise the local There are raised defences at Holt, community to encourage people Rossett, Aldford, Eccleston and at risk to take action to help Trevalyn. Raised defences upstream themselves. of Shocklach protect agricultural land and buildings against flooding from the River Dee. There is a land drainage pumping station at Trevalyn.

Holt Meadows in flood

18 Environment Agency Wales River Dee Catchment Flood Management Plan Sub-area 6

Deeside, Wirral and North Flintshire

Our key partners are: The River Dee channel between Defences will continue to have Chester Weir and the estuary mouth a dominant role in reducing the Local Authorities and communities is canalised with substantial earth likelihood of flooding, but we will defences on both sides. These seek a broader range of integrated Landowners and managers reduce the likelihood of tidal actions to manage both current Water companies flooding, however tidally influenced and future flood risks. flooding remains a significant risk CCW to low lying areas. We will continue to maintain our defences, but it may not be Local Industries Approximately 1,250 properties are justifiable or acceptable to increase currently at risk of flooding from a their height in the future. Emergency Services 1% AEP river flood event increasing to around 1,700 in the future. The outcome we seek is a The dominant source of flooding complementary set of flood risk is the River Dee. management actions by all partners The issues in this at a local community level. These sub-area Tidal levels can restrict the outflows will include: from watercourses and drainage This area includes the Dee Estuary systems and exacerbate flooding • increased emphasis on actions and the urban areas of Deeside, behind defences. to manage the consequences Sealand, Flint, Holywell, Neston, of flooding from all sources; Heswall and West Kirby and large • increased community and tracts of agricultural land. The vision and individual awareness of their flood risks and adoption of This area is important as a major preferred policy actions both can take to industrial centre with large Policy Option 5 – areas of moderate help themselves. industrial plants and commercial to high flood risk where we can premises such as Corus and Airbus. generally take further action to Deeside and Sealand conurbations reduce flood risk. Actions to implement are very flat with large areas of land below high spring tide levels. This is a heavily urbanised area the policy include: with a complex interaction of flood sources and environmental We will develop a Tidal Dee Flood features. In the future, sea level rise Risk Management Strategy to identify and additional development could the appropriate mix of actions to increase the flood risks considerably, manage flood risk from all sources, unless these are managed. now and into the future. We will engage with and seek the support This area is dependent on flood of our partners to this strategy. defences to reduce the likelihood of flooding Overtopping of This strategy will inform and be defences, now or in the future, informed by the North Wales and by extreme flood events could North West England SMP. have serious consequences. Northern embankment on the tidal River Dee

Environment Agency Wales River Dee Catchment Flood Management Plan 19 Sub-area 7

Chester

Our key partners are: The dominant source of flooding management actions by all partners is the River Dee. Tidal levels at a local community level. These Cheshire West and Chester Council can restrict the outflows from will include: watercourses and drainage Local communities systems and exacerbate flooding • increased emphasis on actions to manage the consequences Water Companies behind defences. of flooding from all sources; CCW Main roads and infrastructure installations are also at risk of • increased community and Emergency services flooding. The River Dee SAC, individual awareness of their flood parkland and open spaces are risks and adoption of actions both exposed to flooding. can take to help themselves.

The issues in this Raised defences on the canalised sub-area section of the River Dee from Actions to implement Chester Weir to the A548 road the policy include: This area includes the city of bridge protect Chester against tidal Chester and its immediate suburbs. and river flooding. In the low lying Encourage and support our partners It is a densely populated urban area areas to the west of the city on the to produce local long term plans interspersed with open spaces and north bank of the River Dee, raised to manage all sources of flooding parks and is a major commercial defences protect residential and at Chester. These plans should area in West Cheshire. commercial property. include an assessment of the consequences of flooding, including Approximately 600 properties are from overtopping of defences, and currently at risk of flooding from a actions to manage these. They 1% AEP river flood event, increasing The vision and should consider future options and to around 1,800 in the future. preferred policy investment needs for defences, Policy Option 5 – areas of moderate emergency planning and response, to high flood risk where we can and development control issues to generally take further action to avoid inappropriate development reduce flood risk. in high risk areas.

Defences will continue to have Engage and advise the local a dominant role in reducing the community to encourage people likelihood of flooding, but we will at risk to take action to help seek a broader range of integrated themselves. actions to manage both current and future flood risks. Flood risk management actions will inform and be informed by the We will continue to maintain North Wales and North West England our defences, but it may not SMP and the Tidal Dee flood risk be justifiable or acceptable management strategy. to increase their height in the future. The outcome we seek is a complementary set of flood risk

Chester Weir at low tide

20 Environment Agency Wales River Dee Catchment Flood Management Plan Sub-area 8

Mold

Our key partners are: Many locations within Mold • increased community and and outlying communities are at individual awareness of their Flintshire County Council risk of flooding from surface water flood risks and adoption of run-off, local watercourses and actions both can take to Local communities drainage systems. help themselves. D∑r Cymru Welsh Water Mold is one of the major areas in Flintshire identified for residential, Actions to implement commercial and industrial growth The issues in this in North East Wales/West Cheshire. the policy include: sub-area Encourage and support our partners to produce local long term plans This area is centred around the The vision and to manage all sources of flooding towns of Mold and Rhydymwyn and preferred policy at Mold. These plans should is predominantly urban. include an assessment of the Policy Option 4 – areas of low, consequences of flooding, including Approximately 440 properties are moderate or high flood risk where from overtopping of defences, and currently at risk from a 1% AEP flood we are already managing the flood actions to manage these. They event, increasing to around 540 risk effectively but where we may should consider future options and in the future. Flood defences have need to take further actions to keep investment needs for defences, recently been constructed to reduce pace with climate change. emergency planning and response, the likelihood of flooding direct and development control issues to from the River Alyn. Our vision includes improved integration of actions by all parties avoid inappropriate development Culverts and flow constrictions on to manage all sources of flood in high risk areas. the tributaries of the River Alyn also risk, particularly local surface Work with partners to deliver over increase the likelihood of flooding water and sewer flooding in time increased naturalisation of in Mold. Mold and Rhydymwyn. watercourses and a reduction of Increased naturalisation of constrictions to flow and culverts watercourses and a reduction of in Mold. constrictions to flow and culverts. Encourage and support studies by Particularly in urban areas, partners to identify surface water e.g. Mold. and sewer flooding issues and We will continue to maintain management options, in Mold our defences, but it may not be and Rhydymwyn. justifiable to increase their height in Include the Mold area in the River the future. Our vision also includes: Dee Flood Forecasting Model.

• increased emphasis on actions Engage and advise the local to manage the consequences of community, to encourage people flooding from all sources; at risk to take action to help themselves.

Mold Flood Alleviation Scheme, implemented in 2006

Environment Agency Wales River Dee Catchment Flood Management Plan 21 Sub-area 9

Bangor-on-Dee

Our key partners are: Localised flooding in the north of Actions to implement the town is managed by a pumping Wrexham County Borough Council station which removes storm water the policy include: back-up when river levels are high. Local communities Encourage and support our partners to produce a local long The two main sources of flooding D∑r Cymru Welsh Water term plan to manage all sources are from overtopping of the of flooding at Bangor on Dee. CCW defences upstream of the town at This plan should include an Bangor racecourse and backing-up assessment of the consequences of drainage systems within the of flooding, including from town during high river flows. The issues in this overtopping of defences, and sub-area actions to manage these. The The vision and plan should consider future This area consists of the small, options and investment needs for mainly residential area of Bangor- preferred policy defences, emergency planning and response, and development on-Dee on the east bank of the River Policy Option 4 – areas of low, Dee. It sits within the Middle Dee moderate or high flood risk where control issues to avoid sub-area. we are already managing the flood inappropriate development in risk effectively but where we may high risk areas. Approximately 370 properties are need to take further actions to keep currently at risk from a 1% AEP flood We will continue to maintain our pace with climate change. event, increasing to around 390 defences and provide properties in the future. Our vision includes improved flood warnings. integration of actions by all parties There are flood defences at Bangor- Encourage and support studies by to manage all sources of flood risk, on-Dee and upstream. In general, partners to identify surface water particularly local surface water and ground levels are one to two and sewer flooding issues and sewer flooding. metres below the 1% AEP flood management options. level and the defences are high in This community is very dependent Engage and advise the local relation to some of the properties. on flood defences to reduce the community, to encourage people Any overtopping or breach of the likelihood of flooding. We will at risk to take action to help defences could have very serious continue to maintain our defences, themselves. consequences. but it may not be justifiable or acceptable to increase their Encourage and support height in the future. Our vision opportunities upstream in the also includes: catchment, to reduce local run-off through changes in • increased emphasis on actions land management and thereby to manage the consequences potentially reducing peak flood of flooding from all sources; levels at Bangor-on Dee. • increased community and individual awareness of their flood risks and adoption of actions both can take to The Old Dee Bridge in Bangor-on-Dee help themselves.

22 Environment Agency Wales River Dee Catchment Flood Management Plan Sub-area 10

Bala

Our key partners are: Approximately 470 properties • increased emphasis on actions are currently at risk from the 1% to manage the consequences of Gwynedd Council AEP river flood event, rising to flooding from all sources; around 560 properties in the Local communities future. Flooding in the present is • increased community and individual awareness of their Snowdonia National Park Authority likely to be shallow and would generally lead to minor community flood risks and adoption of disruption. actions both can take to help themselves. The issues in this Climate change is expected to be sub-area the main cause of increased flood risk in the future. Actions to implement This area includes Bala town and Lower sections in the defences the policy include: its immediate surroundings. It is north of the town reduce the a small town in the Snowdonia Encourage and support our effective level of protection to Bala. National Park with mixed partners to produce a local long The standard of protection of raised residential, commercial and light term plan to manage all sources of defences in the south west flank of industrial areas. Tourism is an flooding at Bala. This plan should Bala, depends on lake water levels important means of income to include an assessment of the which are regulated but which local retailers and services. consequences of flooding, including are also open to natural lake from overtopping of defences, and The main flood risk is from the level fluctuations. actions to manage these. The plan River Tryweryn to the north east should consider future options and of the town and wave action from investment needs for defences, Llyn Tegid (Bala Lake). This causes The vision and emergency planning and response, overtopping of the defences on preferred policy and development control issues to the south west flank of the town. avoid inappropriate development in Localised surface water and sewer Policy Option 4 – areas of low, high risk areas. flooding are also an issue. moderate or high flood risk where we are already managing the flood Encourage and support studies by risk effectively but where we may partners to identify surface water need to take further actions to and sewer flooding issues and keep pace with climate change. management options.

Our vision includes improved Engage and advise the local integration of actions by all parties community, to encourage people to manage all sources of flood risk, at risk to take action to help particularly local surface water and themselves. sewer flooding. Encourage and support an We will continue to maintain assessment of the impacts on the our defences, but it may not be operational regime of Bala Lake of justifiable or acceptable to increase climate change, particularly with their height in the future. Our vision respect to flood risk management. also includes:

Llyn Tegid (Bala Lake) foreshore 2009

Environment Agency Wales River Dee Catchment Flood Management Plan 23 Map of CFMP policies

Legend

Preferred Policy

■■ Policy 2

■■ Policy 3

■■ Policy 4

■■ Policy 5

River Network

7 6 8

2 4 5

9 1 3

km 0 2.5 5 10 15

24 Environment Agency Wales River Dee Catchment Flood Management Plan ■■ Sub-area 1 – Upper Dee ■■ Sub-area 6 – Deeside Wirral Flood risk is low to moderate for the present and and North Flintshire future. Where risk increases in the future this will The current and future flood risk is high, particularly be managed by reprioritising current flood risk along the river corridor, in low lying flat areas of management activities. Deeside and Sealand, and in towns along the estuary border. We will need to take action now and in the ■■ Sub-area 2 – Main Alyn future to lower the risk of flooding to communities. Flood risk is low to moderate and is not expected to increase significantly in the future. Where risk does ■■ Sub-area 7 – Chester increase this will be managed by reprioritising current The current and future flood risk is high and the flood risk management activities. disruption and damage caused by flooding is currently potentially high. We will need to take action now and ■■ Sub-area 3 – Middle Dee in the future to lower the risk of flooding to communities in Chester. Flood risk is comparatively low and is not expected to rise significantly in the future. Through adopting different land drainage management practices we ■■ Sub-area 8 – Mold would expect to be able to reduce reliance and The present and future flood risk is moderate to high expenditure on these. overall, with an increase in the extent of flooding in the future. Following an integrated management ■■ Sub-area 4 – Wrexham approach we will respond to the increased risk to these communities in the future with actions to The current and future flood risk from river flooding sustain the present level of service. to this area is moderate. Flood risk does increase in the future and is intensified by urban drainage issues. Flood risk management activity will need to increase ■■ Sub-area 9 – Bangor-on-Dee to sustain the current level of protection into the future. There is potentially a high risk to this community at present and a high risk in the future due to increased ■■ Sub-area 5 – Lower Dee river flows. Flood risk management activity will need to increase in response to the increasing risk posed Flood risk is low across this area as a whole for the by future change. present and future. Where risk increases for specific communities in the future, this will be managed by reprioritising current flood risk management activities. ■■ Sub-area 10 – Bala The present risk is potentially high in Bala and the future flood risk high. Flood risk management activity will need to increase in response to the increasing risk posed by future change.

Environment Agency Wales River Dee Catchment Flood Management Plan 25 Would you like to find out more about us, or about your environment?

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