Aipedia: Landscape architects

AI in SuDS and landscape drainage design

Aipedia, by the Apex broking team · Last reviewed 2026-10-30

AI tools can suggest sizes for rain gardens, swales and basins, but landscape architects should only sign off sizing they are competent to check, with the engineer's role agreed in writing. Flooding claims are costly and often involve several consultants.

Part of: AI in Landscape architects

In short

Landscape-led SuDS blend planting, levels and water management, and AI tools can offer quick sizing for rain gardens, swales, tree pits and attenuation. Those figures depend on rainfall data, infiltration rates and catchment areas the tool may assume or get wrong. LI Rule 6 limits members to work they are competent to deliver, and R4g(c) requires written agreements setting responsibilities. If a feature is under-sized and property floods, claims may be made against both the landscape architect and the drainage engineer, and how PI responds depends on who held the design responsibility and the policy wording.

How AI is used in landscape-led SuDS

Landscape architects design many visible SuDS features: rain gardens, bioretention strips, swales, planted basins, permeable paving edges and tree pits that take run-off. AI tools are used to estimate catchment areas from drawings, suggest storage volumes and feature dimensions, draft planting for wet and dry zones, and write the SuDS sections of design and access statements. Some general-purpose chatbots will produce a plausible sizing calculation on request, with no indication of the rainfall data or assumptions behind it.

Where responsibility sits

The boundary between landscape and drainage engineering is the heart of this topic. The LI Code of Practice sets the framework for dividing it:

Rule 6: only provide services you are competent to deliver; hydraulic sizing and exceedance routing usually sit with a drainage engineer;
R6g: seek advice rather than take on work beyond your competence;
R4g(c) and (d): a written agreement setting scope and responsibilities, with changes recorded, so it is clear who sizes each feature and who integrates it into the landscape.

A common and defensible split is that the engineer sizes and the landscape architect designs the form, levels within agreed tolerances and planting. AI sizing figures from the landscape side should not quietly replace the engineer's calculations. The engineering side is covered in AI flood risk and drainage modelling. If AI-assisted drainage analysis is used in appeal evidence, the Planning Inspectorate's AI casework guidance requires it to be declared, with the checks made.

What can go wrong

AI drainage outputs commonly go wrong in a handful of ways:

catchment areas misread from drawings, omitting roofs or hard surfaces that drain to the feature;
generic rainfall or infiltration assumptions that do not reflect the site;
features drawn smaller during design development, without the volume being rechecked;
levels that stop water reaching the feature or route overflow towards buildings;
planting specified that cannot survive the wet and dry cycle.

Illustrative scenario. On a small residential scheme without a separate drainage engineer for the landscape areas, a practice uses an AI tool to size a series of rain gardens. The tool assumes a higher infiltration rate than the clay soils allow. In the first heavy storm, the features overflow and water enters two ground-floor flats. The developer faces claims from residents and seeks recovery from the practice and the civil engineer, each of whom says the other was responsible for sizing.

How PI usually responds

A flooding claim arising from negligent design is a professional negligence claim, and PI usually responds for the party whose design was at fault, subject to the wording. Where responsibilities were unclear, both consultants' insurers may be involved and the outcome turns on the appointments and correspondence. Appointments with net contribution clauses can limit each consultant to their fair share. Insurers may also ask whether the work fell within the business description on the policy: a practice that regularly performs drainage sizing should say so at renewal. See PI for drainage consultants and does landscape architects' PI cover AI errors?.

Practical controls

Practices can keep AI drainage figures in their proper place with these steps:

agree in writing who sizes each SuDS feature and who checks levels;
treat AI volumes as a check on, not a substitute for, the engineer's calculations;
use site infiltration test results, not assumed values;
re-run sizing whenever a feature shrinks in design development;
show exceedance routes on landscape drawings and coordinate with the engineer;
carry establishment and maintenance needs into the specification and maintenance plan.

Drainage land also needs reserving early in generative masterplans.

How Apex helps

Apex arranges PI for landscape practices whose work overlaps with drainage design. A broker can check that your business description and limits reflect the SuDS work you actually do, and how the policy would treat an AI-assisted sizing error. See the AI in landscape architecture overview.

Sources

Frequently asked

Can a landscape architect size SuDS features?

Only within their competence. LI Rule 6 limits members to services they are competent to deliver, and hydraulic sizing often sits with a drainage engineer. Practices may design the form, levels and planting while the engineer sizes volumes, with the split recorded in the appointment under R4g(c).

Who is liable if an AI-sized rain garden floods a property?

Whoever held the design responsibility for sizing, which depends on the appointments and correspondence. If both the landscape architect and engineer were involved, both may face claims. PI usually responds to the negligent party's share, subject to the policy wording and any net contribution clause.

Do I need to tell my PI insurer I do drainage design?

It is sensible. Insurers rate cover on the activities described in the proposal, and drainage sizing carries different risk from planting design. Under the duty of fair presentation, significant changes in the work you do, including new AI tools for technical tasks, are worth disclosing at renewal.

Check your PI covers how you use AI

Tell us about your firm and the work you do. A broker will review how your current PI treats AI-assisted work, or arrange new cover. No fee for a quote. Or call 0117 325 0027.

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Apex Insurance Brokers Limited is authorised and regulated by the Financial Conduct Authority. Registered in England and Wales, company number 07014570. This page is general information about how AI is used in the profession and how insurance may respond. It is not legal, regulatory or insurance advice on your circumstances, and it does not guarantee that cover will be available or on what terms.