Common Causes of Flood Risks in London
Along with its dense urban development, London’s position on the River Thames makes the capital one of the UK’s most complex areas when it comes to managing flood risk. From tidal influences in the east to heavy rainfall and surface water challenges across built-up boroughs, new developments face heightened scrutiny from planners.
The city benefits from major flood risk management structures – most famously the Thames Barrier, which protects central and eastern London from tidal surges. Even with these defences, long-term flood risk remains, particularly with rising sea levels and climate change projections.
The West London SFRA (Strategic Flood Risk Assessment) and borough-level studies highlight specific hotspots where development proposals need close attention. For example, certain London Boroughs face greater issues with drainage, while others have a history of river and sea flooding.
You could be planning a house extension, contributing to a large housing scheme or working on an individual property. Whatever the situation, any proposed development in the capital needs to carefully consider how it could affect flood risk locally and meet the expectations of both the Environment Agency (EA) and the borough councils.
When You Need a Flood Risk Assessment in London
If your development site falls within areas shown on the flood map for planning, you’ll often need a formal flood risk assessment (FRA). The flood map categorises all of the listed flood zones, ranging from low-risk development in zone 1, through medium-risk areas in zone 2, to high-risk land in zone 3.
Flood zones listed on a flood map, however, aren’t the only factor. You may also need an FRA if your site is over one hectare in size, sits on a functional floodplain or is identified by the borough as having other sources of flooding risk, such as reservoir flooding or groundwater. Even a small planning application for a building extension can trigger the requirement if the site lies within a sensitive area.
Along with the local planning authorities, the lead local flood authority for each borough will expect you to show how flood risk has been assessed and managed. Without an FRA, there’s a good chance your application will be delayed or refused. With one, you can demonstrate that you understand every potential flood risk, have considered the exception test where required, and are addressing both immediate and future concerns.
The Flood Risk Assessment Process
A London FRA is a site-specific survey and report designed to give planners confidence that your planning proposal is safe and sustainable. The process usually involves:
Review Local Context
Assessing your site in relation to nearby rivers, tidal influences and the borough’s planning policies.
Check Flood History and Data
Using risk data from the EA, boroughs and local SFRAs.
Conduct Mapping and Modelling
Considering river and sea flooding, reservoir and surface water scenarios.
Evaluate Site Conditions
Analysing round levels, drainage systems and whether your project is within a functional floodplain.
Test Design Resilience
Exploring how your scheme deals with residual risks, incorporates flood defences, and supports climate change allowances.
Develop Mitigation Measures
Putting together drainage improvements, finished floor levels or changes to the layout to reduce the risk of flooding.
Produce a Clear Report
Creating a document that sets out your approach, mitigation and compliance with policy, ready to submit with your planning application.
For developers, architects and homeowners alike, the structured approach makes it far easier to gain approval and progress projects with confidence.
Why Choose Arbtech for London FRAs
Navigating flood risk in London is rarely straightforward. With 32 London Boroughs and each with different policies, requirements and planning officers, it’s easy for applicants to feel overwhelmed. Our consultants have worked extensively across the capital, meaning we know the local processes inside out and can anticipate what each authority expects to see in a flood risk assessment.
That experience extends from lesser-risk developments like a single building extension in a quiet residential street to large and complex projects in a riskier part of the flood map close to the Thames. In both cases, our role is the same: to make the process easier for you and give your application for planning consent the best possible chance of success.
Clients choose Arbtech because we offer practical solutions, and if your development faces challenges from surface water, tidal influences or drainage limitations, we’ll suggest realistic design changes and mitigation strategies to help you move forward. Our reports are written in plain English, so you and the planners can clearly see how your scheme addresses flood risk and complies with local and national policy.
We also understand the pressures of development timelines. That’s why we aim for a rapid turnaround, often completing assessments within a week. And unlike many providers, we never add hidden costs for travel or accommodation. Instead, our nationwide coverage means you benefit from local expertise without paying extra.
Book Your London Flood Risk Assessment
If you’re preparing a planning application in London, now is the time to arrange your FRA. Our reports are accepted by local authorities across the capital and give you everything needed to demonstrate compliance.
From a small individual property project to a large-scale proposed development, we’ll assess your specific location, identify any further risks, and recommend practical solutions.
Call us today, email or complete our contact form for a free quote. With the help of the team at Arbtech, you’ll get a fast and professional service that makes navigating London’s flood risk and planning policies simple and stress-free.
