Guidance

Reservoir owner and undertaker responsibilities: on-site emergency flood plans

Updated 25 June 2021

It is a legal requirement for all undertakers (owners and operators) to prepare an on-site emergency flood plan for all large raised reservoirs in England, including reservoirs under construction.

The flood plan outlines what areas could flood and the actions needed to prevent, control and mitigate an uncontrolled release of water that could cause flooding from a reservoir.

This guide is to help undertakers to:

• have a clear plan of action to respond to an incident
• prepare the plan
• understand how to test, review and revise the plan

As an undertaker, you are responsible for preparing the plan, and you must consult with an appointed engineer. The appointed engineer needs to certify the plan. Read about the Reservoir panel engineer’s duties - on-site emergency flood plans.

The flood plan should:

• enable you and your staff to respond effectively when needed
• contain enough detail so that staff, contractors, and partners are fully informed and ready to take the correct action to prevent or mitigate flooding
• be specific to each reservoir
• be concise and practical
• work in conjunction with the emergency plans for local communities - known as off-site flood plans - not simply rely on emergency services

The plan will ensure the right people can:

• prevent, control and mitigate a flood from the reservoir that could endanger life or property
• minimise and prevent structural failure
• prevent, delay, slow down or divert an uncontrolled release of water to protect local communities, for example, by drawing down the water level
• temporarily repair a breach or structural failure to stabilise the structure until it can be fixed properly

It is good practice for a flood plan to be developed in conjunction with an off-site flood plan if it’s available. The upper-tier local authority or local resilience forum is responsible for an off-site flood plan. Find the contact details for the local resilience forum in your area.

1. Prepare your flood plan

You can use the template for an on-site plan reservoir dam incident as a starting point for preparing the flood plan.

The ministerial direction sets out the minimum requirements that you must include in all reservoir flood plans.

If a flood plan already exists, you can use the template as a checklist to ensure your plan includes the necessary information.

If you do not have a plan in place already, you must have one within 12 months of the letter you received or as otherwise directed.

You must prepare the flood plan in consultation with your appointed engineer, who will need to certify that it contains all the legally required information.

You must prepare a flood plan for any reservoir under construction before the construction engineer issues a preliminary certificate and the reservoir is filled with water for the first time.

2. What to include in the flood plan

The flood plan must describe:

• the name of the reservoir
• the capacity (volume of water) of the reservoir
• a description of the reservoir and its structures
• whether the reservoir is under construction or modification, and a description of the work taking place
• the location of the reservoir and dams, including grid reference
• access details, including maps or a diagram showing access routes, gates, key holders and meeting points
• a description of how the water into and out of the reservoir is controlled

A good flood plan will also describe:

• the surrounding catchments both upstream and downstream of the dam - you may want to include a map
• the purpose of the reservoir, for example, flood risk management, water supply, or amenity
• whether the reservoir is impounding or non-impounding
• the type of construction, such as concrete or earth embankment, or clay core
• information about the reservoir condition
• whether the reservoir is designated high-risk
• the reservoir and dam’s dimensions and features
• the diversion capacity into and out of the reservoir
• if the reservoir is in cascade, any information you have about the other reservoirs
• the dimensions and capacity of the draw-off works

2.1 Roles and responsibilities

As a reservoir undertaker, you are responsible for the flood plan.

You must:

• ensure an effective flood plan is in place
• ensure the right people have the necessary information and training to prepare for and respond to an emergency and know how to manage an incident
• prepare the plan in consultation with their appointed engineer and others

You are responsible for ensuring that the right people are trained to contribute to a robust plan and activate the plan if necessary.

The plan should be clear on who, during an incident, will have overall responsibility and authority. This would normally be the undertaker or a named senior responsible manager who will:

• have the authority to make decisions about the reservoir, including financial decisions
• approve, agree and direct all necessary measures to prevent a situation from worsening
• be responsible for ensuring effective communication with and between key team members, including any emergency responders, engineers, and local communities, in line with the off-site plan

The plan should be clear on all the relevant incident management roles for any incident response on-site.

Responsibilities of the appointed engineer

The appointed engineer should help you to prepare, test and revise a flood plan for your reservoir.

The appointed engineer will be:

• the supervising engineer for high-risk reservoirs
• a qualified civil engineer from either the All Reservoirs Panel of Engineers, the Supervising Engineer Panel, the Service Reservoirs Panel or the Non-Impounding Reservoirs Panel for reservoirs that are designated not high-risk
• the construction engineer for reservoirs under construction

The appointed engineer’s duties include:

• helping you to prepare a flood plan
• certifying that the flood plan meets legal requirements
• directing you about the frequency and method of testing the flood plan

They may direct you on how to revise the plan.

The plan should be clear about the engineer’s role and responsibilities in the event of an incident. This might include attending the site urgently and advising on other suitably qualified people.

The engineer may:

• provide advice on appropriate measures to be taken by the undertaker and Category 1 responders to avert failure or reduce the effects of an actual breach in line with the flood plan
• give an opinion on how, why, and when the failure could occur and what the impacts might be
• advise of the expected off-site consequences of the dam breach so that the information can be passed on to the Category 1 responders

Location of the reservoir and access details

The flood plan should provide enough detail so that people who are unfamiliar with the reservoir would know how to access it. In a worst-case scenario, the appointed engineer, contractors, staff, and others may need to get from the nearest major road to the reservoir in the middle of the night.

A map of the reservoir should be in the plan and include:

• National Grid Reference (NGR)
• geocode (for example, What3words)
• the address
• access routes
• meeting points

Keyholders and security

You should include:

• a schedule of gates, padlocks and keys
• the level of security, for example, any compliance to Loss Prevention Certification Board Standard LPS1175 (BRE, 2005) and, if so, the security level of the building components
• any alarms or other intruder detection systems

Alternative routes to the dam and other features that may be necessary in an emergency

This should include:

• how access routes might be affected by flooding
• alternative access routes if severe flooding in the area of the dam blocks the primary access
• weight, width and height restrictions on-site and on adjacent roads, and vehicle size and weight constraints
• pedestrian-only access and access through third-party land
• the nearest places to park
• where temporary equipment is stored (or can be accessed from), for example, water pumps
• the nearest places to land a helicopter

Access around the dam site and access to structures

This should include:

• access to critical parts of the dams, such as the abutments, all structures along the dam crest and downstream valves
• alternative access routes if some are blocked for any other reason, such as flooding, plant, equipment, or fallen trees
• where temporary pumps and pipes could be sited

2.2 Control of water flows

A flood plan will need to describe:

• how water flows in and out of the reservoir and how to control it
• how to stop water from entering the reservoir and divert it into the wash channels or other temporary storage if pumps manage the inflow of water, whether and how to reverse them

2.3 Supporting information and documents

Information about the regular operation, surveillance, maintenance works, and current or outstanding works at the reservoir should be available in or alongside the flood plan. Include information about how frequently instruments are read, visual inspections, and information about the catchment and water inflow points.

The information needed in the Prescribed Form of Record (water level observations, leakages, settlement, and certificates, reports and details of works) for high-risk reservoirs should be available.

The flood plan must say where essential documents relating to the reservoir are kept and how to access them. Where possible, it is good practice to keep copies of these documents with the flood plan.

Documents that should be available:

• preliminary, interim, and final certificates under section 7 of the Reservoirs Act 1975
• certificate of efficient execution of works and annex
• inspection reports under section 10 or 8 of the Reservoirs Act 1975
• annual statements under section 12 of the Reservoirs Act 1975
• construction drawings
• other records of construction works (original, matters in the interests of safety, other upgrades)
• historical incident and investigation reports
• valve schematics and schedules
• operational risk assessments, both for operational staff and for potential downstream impacts
• reservoir flood maps if available

Other documents that may be useful:

• photographs, instrument readings, and other surveillance data
• feasibility studies for upgrades and rehabilitation works (for example, assessments of spillway adequacy and safety factor against sliding)
• historic maps
• any additional information that would be useful in an emergency

2.4 Risk factors and triggers for activating the flood plan

A robust flood plan will include the risk factors or visual indicators indicating when the reservoir could fail and flood. Various risk factors can have an impact on a reservoir and heighten the risk of a potential failure. For example, extreme weather, including heavy rainfall and prolonged dry periods, can undermine a reservoir’s structural integrity.

It is crucial to understand the risk factors and trigger points to make the correct response, including escalation, quickly. This might include an elevated reservoir level that triggers an overtopping incident or where internal erosion leads to settlement and overtopping or leakage.

Other examples of potential triggers are:

• an earthquake or land landslips affecting the local area
• movement in dam crest and slope
• small uncontrolled release of waters, for example, via an embankment or tunnel
• movement or cracks in an up or downstream embankment
• unusual instrument readings from monitoring equipment
• accidental damage to a dam or reservoir structure
• advice from the appointed engineer
• a structural problem in the dam or its spillway has been reported
• Met Office severe weather warnings for local high intense rainfall
• flood warnings issued by the Environment Agency for the catchment upstream of the dam

The flood plan should include a detailed description of the on-site triggers and action levels, which might include a ‘standby’ situation where there is a possibility for ‘dam breach.’ The description should be easy to read in a format that people can quickly reference in an emergency.

2.5 Immediate assessment protocol

The flood plan must include a clear plan of actions you will take to prevent, control or mitigate a flood, including how and who will be responsible for carrying out an immediate on-site assessment of the situation.

This immediate assessment should include identifying the efforts and resources needed to respond to the emergency and considering the health, safety, and environmental checks relevant to the incident and response. Instructions should be in the supporting information to the plan.

The flood plan must specify the necessary actions to prevent, control or mitigate an unplanned water release.

These will include the location and operating instructions for valves, pumps, and other means to control the water flow, divert water to temporary storage, or deploy additional pumping equipment to reduce water levels in the reservoir.

The flood plan should include the practical steps needed to:

• continuously assess the risks
• monitor changes in the dam’s structure and stability
• make the reservoir safe
• repair and reinforce damaged areas

2.6 Instructions for an emergency drawdown

Drawing down the reservoir is likely to be critical, and depending on the size of the reservoir and volume of water, it may take several days to bring water levels down to a safe level.

You must include instructions on how to perform a reservoir drawdown in the flood plan. Diagrams or annotated photographs may be helpful. When writing the instructions, assume that it could be for someone unfamiliar with the site.

Include a summary of all valves for emergency drawdown, including plans showing the valve locations and identity, the operation method, and the number of turns to open the valve fully.

It should also include:

• the location of any valve and padlock keys that are needed to operate the valves
• the staff resources needed to carry out a full emergency drawdown - for example, if any valves need 2 people to operate them
• how to access additional temporary resources that could speed up reducing the water level, for example, pumps
• a risk assessment of the health, safety, and environmental risks involved in that operation, both to staff involved in the operation and downstream communities and the environment

The plan should include details on the anticipated rate of drawdown, taking into account the time for full opening of the bottom outlet for a range of inflow conditions.

The drawdown capacity should be specified as a percentage of dam height per day so that the drawdown capacity is linked directly to the load on the dam.

Include in the flood plan the points at which:

• the load is halved (generally equivalent to a water depth of 70 per cent of the initial reservoir level)
• the water level is 1m below the spillway overflow level (recognising that some internal erosion incidents are in the upper part of the core)

You should specify other ways to lower the water level if the structural problem relates to the outlet for emergency drawdown or no suitable outlet in the plan.

Include a summary of all the dam heights and cascade levels for reservoirs in cascades.

Practical issues that you might also consider in estimating the drawdown capacity could include:

• whether you can move water to other reservoirs or water treatment works
• washouts on supply lines that could increase the drawdown capacity in an emergency
• other ways of increasing discharge capacity and the effect it will have downstream

A good flood plan will also include information relating to:

• consequential risks that may be created, for example, rapid drawdown causing slope failure of the embankment
• maximum releases from the reservoir that avoid any downstream flooding or property damage

2.7 Reservoirs in cascade – measures at other reservoirs

If other reservoirs are not covered by the flood plan (for example, reservoirs in the cascade owned by a different company), it should say whether these reservoirs’ operations can be changed to prevent or help control an escape of water. This might include temporarily diverting or storing inflows or lowering downstream reservoirs to hold any dam-break flood.

Consider how and where stream courses are culverted and whether measures could be taken to store water behind embankments that are not reservoir embankments such as motorways and railways in extreme cases.

The plan should set out how to liaise with other reservoir managers and undertakers in the cascade, including:

• communication routes between the different managers or undertakers and joint planning
• what preventive actions to take if there is a severe incident at an upstream reservoir
• what, and who will take measures to reduce the dam-break flood wave effect, for example, lowering a downstream reservoir to absorb the flood wave

2.8 Areas that are at risk of flooding

The flood plan must include information about the areas at risk of flooding if a dam fails. This information is essential to inform the incident response needed. Good liaison between the undertaker, engineers, and emergency responders is essential as impacts from flash-flooding caused by an uncontrolled release of water will often go beyond the immediate downstream area.

The flood risk maps produced by the Environment Agency indicate the flooding that would occur if a failure of a reservoir embankment or structure led to an uncontrolled release of water.

Where no reservoir flood risk maps are available, you and your appointed panel engineers should:

• follow the guidance given in the Environment Agency guide to risk assessment for reservoir safety management
• consult relevant authorities
• produce their flood models
• use datasets such as Lidar, ordnance survey, and fluvial flood maps to identify areas at risk

3. Contacts in an incident

The plan should identify the right people, machinery, and materials on-site to secure a breach and include clear instructions on how to contact them.

This includes:

• essential operational and technical personnel and expertise
• equipment on-site and how to operate it
• communications equipment
• other resources needed (labour, materials, including sandbags, plastic sheeting, bulk filling materials, plant including temporary pumping equipment)
• the location and contact details for on-call contractors

3.1 Inform your staff and external partners of an incident

Specify how to let the necessary people know that there is an incident.

Your plan should include:

• contact details (or how to access them) for staff and contractors, including your appointed engineer
• how to alert emergency responders
• contact details for other reservoir users who may need to know that there is an emergency and that the reservoir is closed to the public
• mobile phone coverage details, including mobile phone networks at the site
• the nearest fixed landlines within a minimum of 2 miles outside of the breach flood map outline

Your plan should consider how to manage media interest during an incident.

3.2 External partners

In the event of a potential or actual emergency, you will need to inform and liaise with local partners, who may offer support and, if necessary, be responsible for activating and managing any off-site plans.

The flood plan should include contact details for these organisations, how and when to contact them, and ongoing liaison arrangements.

Local Resilience Forum (LRF)

Local Resilience Forums (LRFs) are multi-agency partnerships made up of representatives from local public services known as Category 1 responders. Their geographical areas are based on police areas.

Examples of representatives making up the forum are:

• emergency services
• the local authority
• the NHS
• the Environment Agency

LRFs are supported by Category 2 responders, such as the Highways Agency and public utility companies. They  also work with partners in the military and voluntary sectors.

The LRF partnership can help with communication and co-ordination between all responder agencies. They would play a role in any incident that could have implications off-site but may also support implementing the actions in an on-site flood plan.

Police

The police should receive the initial alert and invoke the off-site contingency arrangements with LRF partners.

Local Fire and Rescue Service

The Fire and Rescue Service may help you with the emergency drawdown of water by deploying pumps and equipment.

Lead Local Flood Authority (LLFA)

The Lead Local Flood Authority (LLFA) is responsible for the off-site incident response arrangements, including emergency response plans.

In a potential or actual incident, the LLFA:

• will, with the police, receive details of the initial alert and invoke the off-site contingency arrangements
• might help in operations to reduce the likelihood of dam failure as agreed
• might provide technical advice and material support for the on-site response as appropriate

Environment Agency

You must inform the Environment Agency immediately if there is a potential or actual incident impacting a reservoir’s integrity and operation. The Environment Agency would generally be involved in the operational response to an incident needing on-site and off-site activity.

The Environment Agency will decide whether to exercise its emergency enforcement authority powers to make the reservoir safe if you cannot do so.

4. Health, safety, and welfare of responders

The plan should be clear about who has overall responsibility for site operations, including health, safety, and welfare.

Consult staff and the company safety representative when developing these plans.

4.1 Health and safety

A good plan will include details of:

• how to carry out a health and safety assessment for the people responding to the incident
• initial plans to avoid or manage hazards

Hazards may include:

• working alone
• prolonged working and shift working
• working near water
• confined spaces
• leptospirosis
• working at heights
• slipping on steep slopes and wet areas
• adverse weather
• darkness

4.2 Welfare

Your plan should include how to access:

• toilets
• a kitchen, or other facilities to eat and make hot drinks
• a room to use as an office
• space where people can rest
• a room to dry clothes

4.3 Minimise environmental impact

Prepare method statements for any planned releases from reservoirs in advance to manage the risk of adverse downstream environmental impacts.

You do not usually need a permit for discharges made in an emergency to avoid danger to life, but you must take all reasonably practicable steps to minimise pollution.

You must tell the Environment Agency as soon as reasonably practicable that the reservoir will be discharged. Environment Agency’s guidance on reservoir discharges: consents, permits, and risk assessments.

5. Test, review and revise the on-site emergency flood plan

It is a legal requirement in England for the undertaker to:

• test the flood plan in line with the appointed engineer’s directions
• keep the plan under review
• revise the plan in line with the appointed engineer’s directions
• get the plan certified by an engineer before sharing it

Testing the plan ensures that all responders are aware of their responsibilities. It’s also an opportunity to review the plan.

5.1 Testing schedule

You should develop a testing schedule showing the level, type, and frequency of exercise needed. Your engineer will advise on the testing schedule appropriate for each reservoir.

Keep the testing schedule with the plan.

It is good practice to test the flood plan for high-risk reservoirs and those under construction every year. You might want to test the plan alongside the Section 12 assessment completed by the appointed engineer (supervising engineer).

You must test the plans following the engineer’s recommendations. The Environment Agency will monitor compliance.

Testing the flood plan

Testing the flood plan should be proportionate to the reservoir’s type, size and flood risk level.

The emphasis is on testing staff knowledge, equipment, and external co-ordinated communications and actions. The type of testing and who does it should reflect the owner’s organisational structure.

Every test should include a formal debriefing and lessons learned report, with changes made to the flood plan as appropriate, as part of continuous safety improvement.

High-risk reservoirs

Test the plan as a desk-based run-through and a site walkover

Undertakers of high-risk reservoirs should perform a desk-based run-through and site walkover every year as well as the annual review.

This could include:

• reviewing the plan to confirm that the details are correct and that all equipment and relevant operational and technical elements of the reservoir referenced in the plan are functional and work as expected
• an on-site or desk-based run-through of the plan to ensure that all relevant staff and the supervising engineer understand their incident response roles

Test the plan with a full incident simulation exercise

Due to the time and resources involved in a full incident simulation exercise, you should take a proportionate and collaborative approach in deciding when to do it. A full incident simulation exercise ensures that people involved in an emergency response know what to do and manage a response in co-operation with the Category 1 emergency responders.

A full simulation exercise should happen more frequently if a reservoir poses a significant risk to a large community (a high impact probability) or if you have responsibility for several reservoirs.

Examples of how often to test a plan

If you own up to 15 high-risk reservoirs and the reservoirs have a likely low impact, you should perform a full incident simulation exercise at a minimum of one of the reservoirs at least once every 10 years.

The exercise should involve the appointed engineer and include operational staff from the other reservoir sites, those in cascade, and all emergency responders to participate or observe.

If you own 16 or more reservoirs, or an individual reservoir has a high impact probability, you should perform a full incident simulation exercise at a minimum of one of the reservoirs at least once every 5 years.

The exercise should involve the appointed engineer and include operational staff from the other reservoir sites, those in cascade, and all emergency responders to participate or observe.

An exercise should involve personnel in the organisation with a role in responding to a major reservoir incident and should include as a minimum:

• deployment of staff as per the plan requirements
• contacting equipment and materials suppliers to confirm their availability during an emergency
  operation of valves and drawdown facilities

Not high-risk reservoirs

Undertakers of not high-risk reservoirs should carry out a desk-based review and run-through and a site walkover every year. An incident simulation exercise should be at least every 10 years, in consultation with an appointed engineer.

With the appointed engineer’s support, you should share the exercises’ lessons across all reservoirs in the group.

You are encouraged to also share across the industry, including with other undertakers.

5.2 Testing equipment

The routine testing of site equipment is part of the statutory inspection process at a reservoir. Where relevant, the testing schedule to the flood plan should include additional testing of the following equipment:

• the bottom outlet and other drawdown equipment - this would typically include the full opening of the bottom outlet at least every 6 months (read the Environment Agency’s guidance on reservoir discharges: consents, permits, and risk assessments.)
• any communication equipment at the site
• any equipment you own that is used when the on-site emergency flood plan is activated, including equipment brought to the site

You should warn the Environment Agency and downstream communities of any equipment testing and potential environmental impact.

When valves are tested, they should:

• be opened to 100 per cent of travel, with water released from the bottom outlet against full reservoir head into the downstream watercourse
• be open long enough for the water to run clear and be steady flowing (a minimum of 5 minutes)

This ensures no silt or debris becomes trapped in the outlet system, which could pose future operational problems. Only do this if it is safe to do so and will not cause any damage downstream. The emergency drawdown arrangements form part of the system’s operational supply, and testing by releasing water would affect the water supply or damage the downstream watercourse. It may be sufficient for the valves to be opened fully in sequence without releasing water.

5.3 Reviewing and revising the on-site emergency flood plan

You must keep your flood plans under review. Undertakers of both high-risk and not high-risk reservoirs should review, and if necessary revise, the flood plan every year to ensure all the information and instructions are up to date. This review may coincide with the relevant appointed engineer inspection (Section 12 and Section 10) reports.

You should review the plan in-depth every 5 years to ensure the plan is still fit for purpose for high-risk and not high-risk reservoirs. The certification will need to be re-issued.

The appointed engineer can direct you to revise the flood plan to ensure that it is fit for purpose. You must comply with an engineer’s direction.

The section 12 annual written statement by a supervising engineer should include a report about testing of the flood plan (including the routine testing of valves) and any recommendations for revising the plan.

When carrying out a section 10 inspection, the inspecting engineer should consider if the flood plan needs revising. This could be because of measures recommended in the interests of safety (MIOS). For example, the flood plan may need additional safeguards while MIOS works are being planned and carried out, stopping after the MIOS is completed and certified.

High-risk reservoirs

The flood plan should be reviewed and updated:

• at least every year
• before the appointed engineer issues a new section 12AA(3) certificate
• as part of a section 10 inspection
• following every test of the flood plan

Not high-risk reservoirs

The flood plan should be reviewed and updated:

• at least every year
• following every test of the flood plan

Reservoirs under construction

The flood plan should be reviewed and updated:

• at least every year
• as part of Section 6 supervision
• whenever the appointed engineer issues a new section 7(1) (preliminary), 7(2) (interim), or 7(3) (final) certificate
• whenever the appointed engineer issues a new section 12AA(3) certificate if a reservoir is high-risk
• following every test of the flood plan

6. Activating the flood plan

If a flood plan is activated, you should consider:

• starting an incident log
• recording and photographing the initial damage to the reservoir dam

You should identify how to prevent the damage from getting worse and how to make temporary repairs. You may wish to include example templates and instructions to cover this in your plan.

The situation will need to be frequently assessed and updated during the incident. You may wish to include in the flood plan instructions for scaling up the monitoring and analysis of data.

You should seek advice from the appointed engineer about the dam structure’s stability and the on-going assessment of risks during the incident.

Arrangements will likely need to work on a 24-hour basis, with rotas for crucial personnel, engineers, and other contractors. Your plan may need to include deputies for nominated roles.

If you cannot secure the dam, the Environment Agency may use its emergency powers. Ensure your plan includes out of hours contact details for the Environment Agency.

7. Sharing and storing the flood plan

You must share the plans on request with:

• the Environment Agency
• the Local Resilience Forum (LRF)
• other Category 1 responders
• the relevant reservoir panel engineers

Undertakers for reservoirs near each other should share and link their plans to understand what to do if one reservoir breaches and risks another flood.

The flood plan should be available electronically so that you can share it securely with all those who need to see it. This will include directly employed staff, contractors and emergency responders.

Keep preferably 2 paper copies on-site, so they are immediately accessible.

Only rely solely on electronic copies if you have reliable access to them and have back-up power to a server where the data is stored. Back up the data regularly. Consider data security and practical accessibility on-site, including digital download speeds for electronic records.