Understanding Product 4 Data: What It Is and Why It Matters

We often receive questions and follow-ups from clients regarding Product 4 (P4) data, as it’s often the reason a report is being delayed. This can understandably cause frustration and stress for the client as the report is almost ready to go but everything is waiting on a data set that they may not fully understand.

And that’s fair enough, neither should they, the data set’s name doesn’t tell you anything about it nor why it matters. It can often feel to clients like they understand that they’re waiting for something important but not quite sure why.

This blog aims to answer these questions by explaining what Product 4 data is, why it’s worth the wait, and some of its limitations.

What is Product 4 Data?

Product 4 datasets are primarily designed to inform Flood Risk Assessments (FRAs), which are required under planning regulations where Flood Risk Standing Advice applies. Product 4 data is the most detailed modelled flood data held by the Environment Agency (EA).

Product 4 data is requested on a site-by-site basis from the Environmental Agency under the Freedom of Information Act 2000 and Environmental Information Regulations 2004. Importantly as the data requested under Environmental Information Regulations (EIR) 2004, the EA has up to 20 working days to respond to our request for data. This is a significant amount of time for clients under tight deadlines.

Typically, Product 4 is supplied as a collection of datasets that provide detailed information on flood extents, depths, velocities, and hazard ratings for a larger variety of probability scenarios. Of particular interest are modelled flood extents and depths for climate change allowances. This data dictates whether a development is feasible and sustainable within in proposed location as it is essential for an FRA to demonstrate that the development will be safe over its lifetime. These data outputs are presented in various formats depending on when and how the model was run.

The Environment Agency commissions modelling for its Product 4 data on a catchment-by-catchment basis. Each model is scoped, built, and calibrated separately to reflect local flood mechanisms. This approach leads to variations in the quality and availability of data provided by the EA for different areas of the UK.

At FPS Environmental, we also use Product 4 data for its insight in our Flood Mitigation Reports and Home Buyers Reports, as it allows us to consider the likely impacts of climate change when suggesting mitigation strategies.

Why Is Product 4 Data Important for Flood Risk Assessments?

In the context of an FRA, by accounting for climate change, Product 4 data allow us to anticipate flood depths changes at the property into the future so ensuring that the development is safe for its lifetime. This informs the recommended Finished Flood Level of a property as we need to ensure it’s high enough to prevent water ingress.

Product 4 models provide modelled flood levels for different return periods; these are presented as metres above Ordnance Datum (m aOD). This forms the foundation for the flood depth calculations. The difference between flood level and the LiDAR derived ground level, is the anticipated flood depth.

The National Planning Policy Frameworks (NPPF) requires a development to be safe from flooding for its lifetime (100+ years for residential developments). For residential developments the 1% AEP (1 in 100 year) + climate change allowance is the standard requirement as per the EA’s Standing Advice. ‘Central’ allowance for most residential areas is typically +35% to +42% (depending on river basin, epoch 2070-2115). The 1% + CC scenario represents a reasonable worst-case for the development’s lifespan and so offers safety with practicality.

A freeboard height is the extra height the finished flood level should have above the predicted flood level. This is an additional safety margin that helps account for the model’s inherent uncertainty. The EA has a minimum 300mm freeboard as standard, 600mm freeboard often required in higher risk areas.

Developments Finished Floor Level (FFL) = Modelled 1% AEP + CC Flood Level + Freeboard.

This helps ensure a development is safe against its own risk.

As mentioned above, here at FPS Environmental we not only use Product 4 data for FRAs where they are a requirement, but also for our Home Buyers and Flood Mitigation reports.

The 20-day response period can cause significant delays to our client’s decisions, we deem the wait worth it. Product 4 data provides us with critical insights that enable us to give our clients industry leading advice on their risk profile both today and into the future, when considering climate change. It forms the foundation of our analysis when advising on the most suitable and sustainable mitigation strategy.  Understanding future depths and likelihood of flooding at a property can vastly change the recommendations of a report and for the client may mean the difference between purchasing a property or not.

Limitations and Challenges of Product 4 Data

The main drawback of Product 4 data is the waiting time, but that’s not the only challenge. Sometimes the data supplied is incomplete, low-resolution, or outdated. In some cases, the EA may have no relevant data at all for a particular area.

From a Flood Consultants perspective P4 data sets can be inconsistent in the way the data is presented and what data is contained within, if any at all. This may lead to further delays for the client as we may have to go back to the EA requesting alternative data sets.

More recently due to cost savings there has been a general shift by the EA away from supplying the more refined Product 4 data sets to providing the raw data in the form of Product 6 data. Analysing Product 6 data is far more involved:

• The files are often over 10 GB and must be uploaded into GIS software for manual data extraction.

• The download and processing stages can take half a day or more.

• The data must often be reformatted before it can be presented clearly and accurately to clients.

While this adds time and complexity, it also means we’re working directly with the most granular model outputs available.

Final Thoughts: Is Product 4 Data Worth the Wait?

We hope this blog has helped translate what Product 4 data is, explaining its importance, how it’s used but also highlighting some of the drawbacks.

Although waiting for Product 4 data can be frustrating, it’s a key ingredient in providing accurate, reliable, and future-proof flood risk advice, ensuring that clients make informed decisions with the best data available.

If you’re navigating planning requirements or simply want to better understand the flood risk at a property, we’re always happy to help clarify the data and what it means for your situation. Whether you’re a developer, homeowner, or consultant, feel free to reach out with any questions, our team is here to support informed decisions.