Guidance

Flood Guidance Statement user guide

Published 1 November 2022

Applies to England and Wales

1. Overview

The Flood Guidance Statement (FGS) is a 5-day risk-based product for England and Wales. It:

• is produced by the Flood Forecasting Centre (FFC)

• shows the forecast level of flood risk for the coming 5 days for surface water, river, groundwater and coastal flooding

• uses a detailed risk matrix approach, based on a combination of likelihoods and impacts

• forecasts at a local authority scale

• provides a summary forecast for the 6 to 10 day period where necessary

Our ability to assess flood risk varies and is affected by the:

• forecast lead time
• weather
• nature of catchments and coastlines
• condition of assets such as flood defences

The FGS provides an assessment of the reasonable worst-case scenario for flood impacts.

The reasonable worst-case scenario:

• is the forecaster’s assessment of the upper range of rainfall, river or groundwater levels or coastal conditions and impacts that may occur
• identifies situations that could cause flooding, threaten communities and pose a risk to lives and livelihoods

2. FGS users

The FGS provides a daily flood risk forecast to assist with strategic, tactical and operational planning decisions for:

• the UK and Welsh governments

• Category 1 and 2 responders

• other organisations involved in emergency and flood response

A public 5-day flood risk forecast is available from the Environment Agency and Natural Resources Wales. These services are for users outside the emergency response community.

The FFC also produces a Flood Outlook product for planners who need to make decisions at a timescale of 6 to 30 days.

3. FGS production and issue

The FGS is:

• issued by the FFC every day by 11.00am and at other times if the flood risk assessment changes
• produced by the FFC with the Met Office and local Environment Agency and Natural Resources Wales flood forecasting teams

It presents the best combined understanding of overall flood risk based on:

• weather and flood forecasts
• catchment conditions
• the operational status of flood defenses and other assets

4. Signing up for the FGS

You can sign up to receive the FGS:

• digitally, through the Met Office’s Hazard Manager

• by email from the FFC

The FGS is also:

• posted on Resilience Direct as a PDF when the overall flood risk is coloured yellow or above

• available through an Application Programming Interface (API) for developers

4.1 FGS on Hazard Manager

Signing up for the FGS through Hazard Manager allows you to:

• view the FGS clearly on computer, tablet or mobile
• view county and risk areas maps interactively
• use other features, such as filtering by flood source or setting your personalized map views
• access the PDF version if required
• access Met Office weather and warnings, other hazard advice and services in one portal

Separate user guides and videos to help you get started on Hazard Manager are available at the Hazard Manager Help Centre

4.2 FGS by email

Signing up for the FGS by email allows you to:

• receive the FGS as a PDF each day into your inbox

• select which local authority areas you are interested in

• select whether you wish to receive the FGS at different flood risk levels - we advise signing up for all risk levels so you receive all the information available in the lead up to any floods

• sign up for the FGS text message service

We encourage individuals to register rather than using generic accounts so we can:

• maintain contact details

• circulate service messages

• provide user guide updates

• keep you up to date with training and other support available

Personal information for Hazard Manager and email users is managed in line with the Met Office privacy policy.

4.3 Resilience Direct

The FGS can be downloaded in PDF version from Resilience Direct.

If you have a Resilience Direct account, these can be viewed on the Flood Forecasting Centre group page.

Currently, the FGS is uploaded to Resilience Direct:

• when the overall flood risk is coloured yellow or above

• some time after the FFC issue time – to get the FGS and updates as soon as they are issued, we recommend using the Hazard Manager or email options

4.4 Application Programming Interface (API) for developers

The FGS is available as Open Data through an API.

All parts of the FGS are available in a digital format, including:

• thumbnail maps

• trends

• text

• flood risk areas
• public 5-day flood risk forecast

For more information contact FFCenquiries@environment-agency.gov.uk.

5. Training and support for the FGS

As well as this user guide, other support to help you understand the FGS includes:

• a series of short training videos

• the Hazard Manager flood guidance user guide

• drop in webinars

• bespoke training and materials for your organisation

For more information on webinars and how we can help your organisation contact FFCenquiries@environment-agency.gov.uk.

To discuss the content of the FGS with a hydrometeorologist you can speak to us directly on 0330 135 4400.

The FFC operates a 365 day, 24 hour service.

6. Summary of FGS sections and features

The main features of the PDF version of the FGS are:

Issue time and date

At the top left of the front page.

Daily maps by local authority areas

At the top the front page. Maps of England and Wales show the overall flood risk from any flood source for each of the next 5 days.

Trend arrow

Below each map. The trend arrow gives a national overview of the forecast trend direction for that day, compared to the previous FGS issue.

The trend can be increased, decreased or steady.

Headline

Below the maps. The headline states:

• the overall flood risk
• shows the highest overall flood risk in the forecast, when there are numerous possible events

This enables users to understand rapidly the scale of any action which may be required.

Amendments in this update

An optional section when an updated FGS is issued. It provides the reason for the update, for example to:

• amend a forecast
• add extra information
• correct a mistake

Specific area of concern maps

One or more detailed maps are included as needed, even for very low risk situations when minor impacts are possible. Each flood risk area is labelled with a letter (A, B, C…..) and shows the:

• impact
• likelihood
• flood source
• duration
• position in the flood risk matrix
• any additional information

When there are sources of flooding with different risk levels within an area, this is shown in the matrix.

Assessment of flood risk

A text summary of:

• the flood risk for surface water, river, coastal/tidal and groundwater flooding
• additional useful information not shown on the area of concern maps - for example, extra geographical details or underlying causes of flood risk

The colour of the bar (green, yellow, amber, red) above each summary represents the highest risk level for that source of flooding.

6 to 10 day forecast

Description of any significant or severe flood impacts forecast in this period will be included as needed.

Next statement due

Note of when the next planned FGS is due each day. This is particularly useful in periods of heightened flood risk when multiple statements may be issued.

Contact details

Contact details to discuss the content of the FGS with a hydrometeorologist.

For detailed local discussion we advise you to use your local Environment Agency, Natural Resources Wales and Met Office Civil Contingency Advisor contacts.

Summary flood risk matrix and potential impacts

At the end of the statement. This contains, for easy reference:

• the flood risk matrix

• description of potential minimal, minor, significant and severe impacts

7. Flood Risk Assessment and matrix

The FGS assesses the flood risk for each local authority area in England and Wales, for all sources of flooding.

The risk is based on a combination of likelihood and impact and presented in a 4x4 matrix.

The matrix has:

• 4 levels of impact on the horizontal axis – minimal, minor, significant, severe
• 4 levels of likelihood on the vertical axis – very low, low, medium, and high

The combination of likelihood and impact gives the overall flood risk – very low, low, medium and high.

The overall flood risk is represented by a colour:

• green for very low

• yellow for low

• amber for medium

• red for high

This is also shown in Table 1 and Figure 1.

Table 1: Flood risk matrix

High likelihood	Very low risk (green)	Low risk (yellow)	Medium risk (amber)	High risk (red)
Medium likelihood	Very low risk (green)	Low risk (yellow)	Medium risk (amber)	Medium risk (amber)
Low likelihood	Very low risk (green)	Very low risk (green)	Low risk (yellow)	Medium risk (amber)
Very Low likelihood	Very low risk (green)	Very low risk (green)	Low risk (yellow)	Low risk (yellow)
	Minimal impact	Minor impact	Significant impact	Severe impact

Figure 1: Flood risk matrix

7.1 Flood risk matrix guidance on impacts

Table 2 shows examples of impacts from flooding for each level in the matrix – minimal, minor, significant and severe.

Impacts are assessed at the local authority level.

Table 2: Flood impacts table

	Minimal impacts	Minor impacts	Significant impacts	Severe impacts
Risk to life	Not expected	Individual risk for the more vulnerable or for those making decisions in unfamiliar situations	Danger to life from fast flowing/deep water/wave overtopping/wave inundation and physical hazards (for example, getting stuck in water)	Danger to life from fast flowing/deep water/wave overtopping/wave inundation and physical, chemical or utility hazards (for example, electrocution)
Communities	Isolated and localised flooding of low-lying land and roads	Localised flooding of land and roads	Some communities temporarily inaccessible due to flooded access routes	Communities cut off
Communities	Isolated instances of spray/wave overtopping on coastal promenades	Localised flooding (inc. waves) affecting individual properties	Flooding affecting properties and parts of individual or multiple communities	Widespread flooding affecting large numbers of properties and whole communities
Communities	Not expected	Local damage due to age and/or condition of structure	Damage to buildings/structures	Extensive damage to and/or collapse of buildings/structures
Transport	Little disruption to travel although wet roads and fords could lead to difficult driving conditions	Local and short term disruption to travel	Widespread or long duration disruption to travel. Damage to transport network (some route closures)	Widespread and long duration disruption to travel. Motorists becoming stranded. Widespread damage to transport network and widespread route closures
Utilities	Not expected	Localised and short term disruption to utilities and services	Disruption to utilities and services	Widespread/prolonged disruption through loss of utilities and services

7.2 Flood risk matrix guidance on likelihood

Table 3 shows examples of how the likelihood of impacts might be described in the FGS.

Table 3: Flood likelihood table

	Very Low	Low	Medium	High
	Possible but not expected	Possibly / Possible	Probably / Probable	Expected
Examples	Minor impacts are possible but not expected due to high river levels in…	Minor surface water flooding impacts are possible from further heavy rain in…	Significant flooding impacts due to high river levels are probable across the north east of England…	Minor surface water flooding impacts are expected from further heavy rain in…

7.3 Using the flood risk matrix

When using the flood risk matrix, it is important to assess the combination of likelihood and impact, rather than the overall risk level and colour.

This is because different flood risk assessments can share a common flood risk level and colour.

For instance, a low overall flood risk (colour yellow) could, for example, be one of the following:

• a medium likelihood of a minor impact (quite commonly forecast - minor impacts are probable)

• a low likelihood of a significant impact (fairly commonly forecast - a low likelihood event, but significant flooding impacts are possible)

• a very low likelihood of a severe impact (rarely forecast - a potentially severe event is possible but not expected – often highlighted at longer lead times to give useful early notice)

Similarly, a very low overall flood risk (colour green) could, for example, be one of the following:

• a very low likelihood of minimal impacts (very frequently forecast)

• a low likelihood of minor impacts (very frequently forecast – minor impacts are possible but the likelihood is too low to increase the overall flood risk)

Again, a medium overall flood risk (colour amber) could, for example, be one of the following:

• a medium likelihood of a significant impact (a more unusual forecast - significant flood impacts are probable)
• a low likelihood of a severe impact (severe impacts are possible but not expected)

High overall flood risk is only forecast when there is:

• a high likelihood of severe impacts

Each of these risk profiles might result in a different response.

8. Forecasting glossary

The key concepts we use in preparing the FGS are:

• risk is a combination of likelihood and impact

• certainty and uncertainty exist in forecasting both likelihood and impact

• confidence is used to qualify our forecasts - it is usually described as low, medium or high, taking uncertainty into account

The main definitions we use are:

Impact

The effects of flooding on people and the environment. For flooding we categorise impacts as minimal, minor, significant or severe.

Likelihood

The chance of something happening, normally in terms of very low, low, medium or high likelihood.

These are often described as possible but not expected, possible, probable and expected.

Risk

The combination of likelihood and impact.

Scenario planning

A method used to plan for the future based on agreed scenarios. For flood forecasting we use 2 scenarios:

• best estimate scenario (what should happen) - a forecaster’s assessment of the middle range of rainfall, river or groundwater levels or coastal conditions and impacts that may occur

• reasonable worst-case scenario (what could happen) - a forecaster’s assessment of the upper range of rainfall, river or groundwater levels or coastal conditions and impacts that may occur

The scenario presented in the FGS is the reasonable worst-case. This means events will often be less severe in reality than forecast in the FGS, especially where there is a lot of uncertainty.

The likelihood of either scenario occurring changes over time. We describe likelihood in terms of possible but not expected, possible, probable or expected.