The rising importance of flood risk surveys to get planning permission, drainage strategies

Rising importance of flood risk surveys to get planning permission

April 1, 2026

Land has long been a valuable asset, but its importance has never been greater than it is today, with rising demand for new housing across the UK. With latest construction techniques and technologies, land that may have previously been discounted for development is now an opportunity. In a world where climate change is a serious issue, increasing the frequency and intensity of rainfall, planning authorities want to see a clear demonstration of flood risk for planning and any mitigating actions.

And this is why the importance of accurate flood risk surveys is rising, so that developers and planners can understand the flood risk potential of an area of land, to determine if safe construction can take place. A flood risk survey is far more than just ticking a planning box – the regulatory National Planning Policy Framework (NPPF) and local climate resilience goals demand robust flood risk surveys to ensure that new developments will last their lifetime and have no negative impact on the surrounding area. The only way to assure them of this is to provide a comprehensive flood risk assessment.”

There have been many instances where planning applications have been refused due to flood risk issues, leading to expensive redesigns, delays and potentially higher insurance premiums, so now is the time to get clued up on planning and flood risk policies for a smoother build project.

What is a flood risk survey?

A flood risk survey is a technical investigation to evaluate all potential sources of flooding affecting a site and present the findings in a formal Flood Risk Assessment (FRA) or flood risk assessment report. For developments in areas known to be high-risk this report is seen as a must have by planning authorities.

A good starting point is to familiarise yourself with the terminology:

Flood Risk Assessment (FRA): A comprehensive document that analyses flood hazards, mitigation measures and compliance policies.
Flood Risk Survey: Often shortened to FRA, this is an on-site survey that collects all the data from topographical, hydrological and drainage information, as well as historical flood records from the Environment Agency flood map for planning.
Drainage Strategy: This plans how foul water and surface water will be managed and may include sustainable drainage systems (SuDS), drainage field design and whether a combined drainage system or separate systems for foul water drainage and rainwater drainage are most suited.

How flood risk surveys support planning applications

An accurate flood risk survey can be essential to the outcome of your application:

Compliance evidence: It provides the evidence to show your proposal meets national and local flood risk and planning requirements.
Site layout and design: Your survey will help you know where to best position your building and access points and the best spot for SuDS features or drainage infrastructure.
Mitigation measures: Finished floor levels, flood resilience measures, compensatory storage or landscape modifications can all be confirmed when a survey is done.
Sustainable Drainage Systems (SuDS): A flood risk survey informs the site’s drainage strategy, addressing rainwater drainage, foul water drainage, drainage field design, and where necessary, engagement with the Lead Local Flood Authority or Drainage Boards.
Faster planning: A clear and properly prepared flood risk assessment report can reduce objections and the chance of repeated requests for clarification or further modelling.

DSA’s experience in flood risk assessments and planning

Living by a river can make for tranquil living but it comes with a potentially higher flood risk. With offices in London and across the UK DSA have helped get planning permission for many developments near rivers in Flood Zone 2 & 3. These include large and small housing developments, self-builds, residential renovations, roads and infrastructure. Most challenging was an historic mill house right on the River Nene situated entirely in Flood Zone 3 where the property owner wished to completely re-level terraces to external areas.

The conclusion is, make sure your planning permission request includes an appropriate and robust flood risk survey, for a smoother and more positive outcome.

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