Who can prepare a Flood Risk Assessment

No statute says who may write a Flood Risk Assessment. The responsibility sits with the applicant, and national policy asks only that the assessment is appropriate to the scale, nature and location of the development. In practice that gap is filled by what councils and the Environment Agency will accept, and it splits roughly in two: a straightforward assessment for minor development that a competent planning or engineering professional can produce, and anything involving hydraulic modelling, which needs a chartered engineer with river modelling experience.

Knowing which side of that line you are on before you commission the work saves both money and a refused validation.

What the assessment has to demonstrate

A flood risk assessment has to answer six questions, and the author's competence is judged by whether the document answers them properly.

Where does the flood risk come from, covering rivers, the sea, surface water, groundwater, sewers, reservoirs and any artificial source. What is the probability of flooding now, and over the lifetime of the development, applying the current climate change allowances. Is the proposed use appropriately vulnerable for the flood zone it sits in. Can the development be made safe, with finished floor levels, resilience measures and safe access and egress. Does it increase flood risk anywhere else. And what residual risk remains if a defence fails or a drain blocks.

An assessment that recites the flood zone and stops has answered one of the six. That is the commonest reason for a holding objection, and it has nothing to do with the author's letters after their name.

Qualifications councils look for

There is no register of approved flood risk assessors, so authorities look at three things: the author's professional membership, the evidence of relevant experience, and whether the document itself is competently written.

The memberships that carry weight are chartered civil engineering status, chartered water and environmental management status through the Chartered Institution of Water and Environmental Management, and chartered environmentalist status. For the drainage side, chartered engineers working in water and drainage design are the usual authors.

Relevant experience matters as much. An engineer who has designed highway drainage for twenty years may never have produced a flood risk assessment, and a planning consultant who has produced fifty may not be able to model a watercourse. Ask for two recent examples of assessments for similar development in similar flood zones, and ask whether the Environment Agency objected to either of them.

The council's own validation list occasionally specifies competence, and some lead local flood authorities publish what they expect from a drainage submission. Read those before appointing. Our note on what competent person means in planning legislation sets out where competence is a legal requirement rather than an expectation, and flood risk assessment sits in the second category.

Where a chartered engineer is expected

The dividing line is whether a number has to be derived rather than looked up.

Looked up covers most minor development in Flood Zone 1 and many schemes in Flood Zone 2 where the Environment Agency already holds modelled levels. The flood zone comes from the published map, the modelled level comes from the Agency's data, the climate change allowance comes from the published tables, and the finished floor level follows from those with freeboard added. A competent professional who understands the policy can assemble that.

Derived covers anything where the flood level, the flood extent, the flow rate or the effect of the development on flood behaviour has to be calculated. Hydraulic modelling, floodplain compensation volumes, flood routing around a site, breach analysis behind a defence, and the assessment of a watercourse where no model exists. That work needs a chartered engineer with modelling experience, because the Environment Agency reviews the method and will ask for the model and its audit log.

Between the two sits the surface water drainage design, which needs a competent drainage engineer even on small sites. Greenfield run-off rate estimation, infiltration testing interpretation, attenuation volume calculation and the design of controls to the Defra non-statutory technical standards are engineering tasks, and the drainage strategy usually forms a separate document alongside the flood risk assessment.

Site-specific modelling and who does it

Where modelling is required, three things distinguish work the Environment Agency will accept from work it will not.

The model has to be built on surveyed data. Channel cross-sections, structure dimensions, bed levels and floodplain topography, measured rather than estimated from mapping. A model built on lidar alone rarely survives review.

It has to be calibrated or at least sensitivity tested. Where historic flood records exist, the model should reproduce them. Where they do not, the assessment should show how the results change when roughness, inflow and structure blockage assumptions are varied.

And it has to be documented. A modelling report or log recording the software and version, the schematisation, the boundary conditions, the return periods run, the climate change allowances applied and the sensitivity tests carried out. Agencies audit that document, not the pretty flood extent map.

If a consultant offers to model a watercourse without a channel survey, treat it as a warning rather than a saving.

Getting the Environment Agency's data and advice

Two routes exist and both are worth using before commissioning modelling.

The first is a data request. The Agency holds detailed modelled flood levels and extents for many watercourses, and will supply the modelled levels for a site on request. If those levels exist, a large part of the modelling case disappears, because the assessment can work from the Agency's own outputs. Ask for the data before anyone quotes for a model.

The second is pre-application advice. The Agency offers a charged advice service for development in areas at flood risk, and for anything contentious in Flood Zone 3 it is money well spent. For minor development the Agency publishes standing advice, which councils apply instead of consulting on individual applications, so read the standing advice first and write the assessment against it.

Where the development is major, the lead local flood authority is the statutory consultee on surface water drainage and has its own expectations. Contact both.

Reviewing an assessment before you submit it

Read the draft with this list beside you. Most of the objections a council raises are avoidable at this stage.

1. Is the flood zone taken from the Flood Map for Planning, with the date it was checked stated in the document.
2. Are all sources of flooding addressed, including surface water and groundwater, rather than rivers alone.
3. Is the vulnerability classification of the proposed use stated, and is it correct. Basement dwellings and some care and residential uses are more vulnerable than people assume.
4. Is the lifetime of the development stated, and is the right climate change epoch and allowance applied for the river basin district. Allowances are updated, so check the version used against the current published tables.
5. Are finished floor levels given to Ordnance Datum, with the design flood level and the freeboard shown separately.
6. Is safe access and egress assessed against depth and velocity rather than simply asserted.
7. Is the sequential approach within the site addressed, and where the sequential test applies to the site as a whole, is that dealt with or explained as unnecessary.
8. Does the document say what happens in an event exceeding the design standard.

Any answer of no on that list is a query you will receive from the case officer in three weeks' time.

Briefing the author properly

Half of the poor assessments in circulation are the product of a poor brief. Send the author a pack before they start.

A topographic survey with levels to Ordnance Datum, covering the site, the access route and the top of bank or channel of any watercourse. The proposed site layout with finished floor levels and external levels. The drainage strategy or the intended approach to surface water. Anything you know about historic flooding, including what neighbours have told you and what the lead local flood authority holds. Any Environment Agency correspondence. The intended use and its vulnerability classification, and the design life you want the assessment to cover.

Then ask for one thing at the end: a statement of who wrote the document, their professional membership and their experience of similar sites, signed. Councils increasingly ask for this, and for an AI-assisted draft it is the reviewer's declaration that gives the document weight. PlanScope's professional directory is the route to that review.

This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it. To see whether your site is likely to need an assessment at all, enter your postcode on PlanScope.

PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval. For specialist technical reports, including hydraulic modelling, qualified professional input may be required.