Flood Risk Assessment FAQs

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Flood Risk Assessment FAQs

What is a Flood Risk Assessment?

Flood Risk Assessment (FRA) is a report that outlines the main flood risks to a development site and presents recommendations for mitigating measures to reduce the impact of flooding to the site and surrounding area.

In a lot of cases, FRAs are required to pass planning permission. This is especially true if your development is within Flood Zone 2, 3a, or 3b. However, there are also situations where it would be necessary in Flood Zone 1, such as if your development is over 1 hectare in total size.

You can read more about FRAs here: What is a flood risk assessment?

What is the purpose of Flood Risk Assessment?

Largely, Flood Risk Assessments are used by the planning industry in order to determine if a new development (from a conservatory extension to a multiple home development site) is sustainable in relation to flood risk.

A significant proportion of the UK is at risk of tidal, river, sewer, or groundwater flooding. However, this does not mean that developments or redevelopments in these areas will not be approved.

Flood Risk Assessment, as part of the planning process, ensures that developers are aware of the recommendations of the Environment Agency (EA) and suggests adequate mitigation measures to ensure that a development is sustainable and safe in terms of flood risk.

Do I need a Flood Risk Assessment?

You will need a Flood Risk Assessment as part of your planning application if your site is over one hectare in size or if it is situated in a Flood Zone. The Environment Agency has a very useful flood zone finder (EA Flood Map) in which you just need to enter the postcode of the development site to find out in which Flood Zone it is located.

Why have I been asked for a Drainage Design/Strategy?

One of the key requirements of the Flood Risk Assessment process is to demonstrate that proposals will not increase flooding elsewhere. As such, surface water must be appropriately managed.

A drainage strategy may be requested by the Local Planning Authority for any site (including sites outside of the river/coastal floodplain) to demonstrate how runoff from the new development will be considered.

How can Ambiental help me?

Ambiental is an experienced Flood Risk Assessment (FRA) consultancy and as such, we work to facilitate and expedite the planning process for our clients.

At every stage of the planning process, we provide our clients with advice and guidance on building design that will reduce the risk of flooding. We have an excellent working relationship with the Environmental Agency and work collaboratively to facilitate the development of sound and sustainable buildings in compliance with the National Planning Policy Framework which currently regulates new development in the flood plain.

You can learn more about what we can support your project on our services page here:

What types of Drainage projects do Ambiental undertake?

Ambiental are skilled in undertaking all forms of drainage assessment and design (including land, surface water and foul).

We specialise in Sustainable Drainage Strategies (SuDS) and Design. Local Planning Authorities and the National Environmental Agencies are getting more stringent in their requirements for developers to manage the surface water for their sites. This is where SuDS Design comes in. We can incorporate surface water strategies into your overall architectural design creating an aesthetically pleasing drainage strategy that is fully National Planning Policy Framework compliant.

Find out more about how our sustainable drainage strategies can help you here:

How quickly can Ambiental deliver a Flood Risk Assessment?

Ambiental usually delivers Phase I FRA reports within 10 to 20 working days of receiving data from the Environment Agency (EA).

Please note that the EA has a statutory 20 working day flood information turn-around time (although in many cases we are able to reduce this time considerably). If time is of the essence, please contact us on 0203 857 8540 for your free quotation.

What is the Flood Risk Assessment process?

A Flood Risk Assessment begins with our clients providing us with the information they hold on the current state of the development site and the proposed plans for what they’re changing it to.

We will then liaise with the Environment Agency (EA) and the Local Planning Authorities (LPA). Then, we assess their requirements with regards to the development and the current legislation. As work progresses, we often act as intermediates between the architects and the Development Control Engineers at the EA, passing on design solutions with regards to flooding.

Finally, a draft report is submitted to both the clients and the EA and once agreed upon a final version is issued for the LPA.

How much will a Flood Risk Assessment cost?

A Flood Risk Assessment (FRA) report can be simple and straightforward and cost as little as a few hundred pounds. However, the more complex sites (such as those which are very large with multiple Flood Zones) can be in the multiple thousands range.

Pricing is case dependent and it is therefore very important for us to gather as much information as possible at the earliest stage in order to give you the most competitive quote.

We also provide a free quoting service so you know upfront how much it would cost and how long it’s likely to take. We pride ourselves on being open and honest with our clients and it’s why we have very strong relationships with our clients as much of our client base has been coming to us for years.

What is the National Planning Policy Framework?

The National Planning Policy Framework came into force in March 2012. It amalgamates numerous previous planning polices into a single planning framework document. Part of the NPPF regulates the assessment of flood risks and their appropriate mitigations to the planning process.

You can read the latest version here:

What is PPS25?

PPS25 refers to Planning Policy Statement 25: Development and Flood Risk. It was the official document that regulated the assessment of flood risks and their appropriate mitigations to the planning process. PPS25 has now been superseded by the NPPF. The PPS25 Practice Guide has now also been cancelled and replaced by the new Planning Practice Guidance.

How does the NPPF fit within the planning process?

The NPPF defines which developments require a Flood Risk Assessment as part of the Planning Application. The NPPF now makes it mandatory for the Local Planning Authority (LPA) to consult with the Environment Agency (EA) on planning applications for sites over one hectare in size or located within Flood Zones 2 or 3.

Who is the enforcing body for the NPPF?

The Environment Agency (EA) enforces flood risk elements of the NPPF and has powers to challenge the Local Planning Authorities (LPA) over development applications in the flood plain.

What are SUDS?

Sustainable Drainage Systems (previously, Sustainable Urban Drainage Systems) can be described as: Planning and designing the process of drainage on a project to mimic natural drainage by attenuating (storing and releasing slowly) runoff, allowing it to soak into the ground, slowly conveying water on the surface, filtering out pollutants, and allowing sediments to settle out by controlling the flow of water.

You can read about our SuDS Services here:

Is there a limit to a drainage strategy that Ambiental will undertake?


What is Ambiental’s position when other consultants are needed?

Our consultancy division regularly works alongside other consultants as part of larger project teams (wither as direct partners, lead- or sub-consultants, or as part of a wider sub-contractor arrangement).

We do this only with companies and consultants we trust and only when we believe it’s the best thing for our clients. Our clients are our top priority, so we only bring in extra help when necessary.

Why does climate change affect flood risk?

The NPPF stresses that there is an increasing body of scientific evidence that the global climate is changing as a result of human activity.

The impact of climate change at a regional level is likely to be variable: for the UK, projection of future climate change suggests that more frequent, high intensity rainfall and periods of long-duration rainfall of the type responsible for the 2000 floods could be expected.

As a result, the Environment Agency (EA) recommends to increase river flows by up to 20% to today’s level to account for the effect of climate change on flood risk.

How accurate is the Environment Agency’s flood map?

The Environment Agency (EA) Flood Zones have been produced using a flood model known as JFLOW. JFLOW has been used to produce the 1% (1 in 100 year) and 0.1% (1 in 1000 year) flood outlines.

The EA acknowledges that the JFLOW method is generalised and does not take flood defences into consideration. As such, the flood outlines produced by JFLOW can only be taken as a rough guide, showing where more detailed flood risk assessments are required.

Can Ambiental carry out flood zone correction?

Ambiental has all the expertise and experience needed to challenge, and in some cases correct, the Environment Agency’s flood maps. Flood zone correction often requires detailed flood modelling.

We would usually recommend that a Desktop Flood Risk Assessment is first carried out in order for us to assess what type of modelling will be required and how much it will cost.

Does Ambiental carry out flood modelling?

Yes, we regularly construct flood models to estimate flood levels directly using commercial packages such as HEC-RAS. We have also developed our own flood model (Flowroute™), further info on which can be found here.

If your question is not answered here, do not hesitate to email it directly to [email protected]

Steven Brown Ambiental Associate

Need an FRA? Get In Touch With Our Flood Risk Team

To get a quote or to discuss what you need, contact one of our Flood Risk Consultants.

Call the team on +44 (0) 1273 006 900  or email at [email protected]

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