17 March 2026
A flood risk assessment is that - a thorough report that takes a hard look at how flooding could wreak havoc on a proposed development and how you'd even hope to mitigate that risk. Commercial and infrastructure projects typically get a lot more scrutiny because of their sheer size, operational importance, and the potential mess they could leave on surrounding areas. The guidance you'll find below outlines what to expect and what you need to do by 2025-2026.
Sites with vast areas and lots of impermeable surfaces tend to have a higher risk of floodwater runoff
Flooding zones can seriously constrain where and how you build
Look out for surface water flooding - this can be a major risk, especially on sites that are already pretty developed
Will you need planning permission and how does that affect things on a large scale?
And, of course, you'll need to take various measures to protect operations and critical assets from flood damage
You'll often need one for things like logistics parks, industrial facilities, retail developments, energy and utilities infrastructure, transport schemes, and public sector assets. Large areas of hardstanding and the potential consequences of flooding are two main reasons why you'll need an assessment.
Flood Zone 1: surface water flooding is still a risk, even if you're not directly in one of the designated flood zones
Flood Zone 2: you'll usually need to justify and mitigate any flood risks to get approval for development
Flood Zone 3: this places significant restrictions on anything that's going to be vulnerable or critical in the event of a flood
Logistics and Warehousing: typically triggered by large impermeable areas, so you'll want to focus on managing runoff and keeping access routes safe.
Industrial Facilities: surface water accumulation is a major risk here, so you'll want to protect your assets and make sure drainage is on point.
Transport Schemes: flood zone crossings or anything else that could disrupt the network will need special scrutiny, focusing on resilience and safety.
Utilities and Energy Infrastructure: this is all about making sure your critical infrastructure is resilient and can keep going during a flood
Work out how to site your development to steer clear of the worst flood-risk areas
Plan your building and plant to be flood-safe and keep them above flood levels
Ensure safe access and egress routes are planned with flood events in mind
Protect your critical assets and services from flood damage
Find ways to manage surface water runoff across big areas
Assessments need to consider how to avoid moving flood risk somewhere else, protecting water quality, and keeping operations running as smoothly as possible during a flood. For infrastructure and essential services, keeping the lights on (even in a flood) is just as important as lowering the risk of a flood occurring in the first place.