CIRIA C821 Explained: Community Maintenance of Flood Risk Assets

CIRIA C821 is a free three-part guidance suite, published in 2025, on how community groups can help maintain local flood risk assets and how the authorities responsible for those assets should work with them. Its value is the line it draws: the work a volunteer can safely and lawfully do on a ditch, a screen or an embankment, and the work that has to stay with an authority, a landowner or a contractor.

Plenty of parish councils and flood action groups already pull branches out of a beck or rake a grille before a storm. Far fewer have written down what they are permitted to do, who agreed it, and who carries the cost if something goes wrong. C821 is the first UK guidance to answer those questions in one place.

The survey behind the guidance found 69 flood volunteers already maintaining assets in England and Scotland, and 21 of them had been at it for more than ten years.

What is CIRIA C821?

CIRIA C821 is Enabling community maintenance for local flood risk management, published by CIRIA in 2025 under project P3235 and free to download. It was written under contract by a consortium led by HR Wallingford with Eunomia, the Flood Hazard Research Centre at Middlesex University, Abertay University and the National Flood Forum. Funding came through the Flood and Coastal Erosion Risk Management Research and Development Programme, with staff support from the Environment Agency's flood and coastal risk management directorate.

The funding list tells you who thinks this matters: the Environment Agency, Flood Re, Hillingdon Council, Network Rail, Severn Trent, Thames Water and the Thames Regional Flood and Coastal Committee. A steering group of 28 people from councils, water companies, the Rivers Trust, the Wildfowl and Wetlands Trust, Natural Resources Wales, SEPA and the Scottish Flood Forum guided the drafting, and 29 named community groups contributed their own experience.

What does community maintenance actually mean?

Community maintenance is voluntary work by a group of local people to watch over and sustain the performance of flood structures, channels and basins in their own area. CIRIA sets the definition out formally, and it repays close reading, because every limit in the guidance follows from it.

The guidance sorts flood volunteering into four kinds of work: knowledge, such as catchment walkovers, gauge readings and citizen science; campaigning, such as awareness work and flood planning; physical work, such as clearing channels, managing vegetation and operating small gates; and virtual work, such as reading remote sensors and keeping the group's records. Community maintenance sits almost entirely in the physical category, with a foot in the knowledge one, because you cannot sensibly maintain an asset you have not been watching.

Three qualifiers matter, and groups trip over the first one most often. The work is done by a group rather than by an individual acting alone, for the benefit of the wider area rather than for one owner or operator, and with the knowledge and support of whoever owns the asset.

None of this replaces technical assessment. Where a development, a planning application or a discharged condition has to demonstrate what happens to water on a site, that is a job for a flood risk assessment for planning, not for a work party.

Which flood assets can a community group maintain?

Watercourses, small trash screens, swales, basins, rain gardens, woody dams, embankment surfaces and road gullies are all in scope, along with short pipe runs that can be cleared from outside. The list is more generous than most groups assume.

• Watercourses. Any stream, river or ditch, along with its banks.
• Short pipe and culvert runs. Only where a blockage in a culvert can be cleared from outside, for example with rods.
• Small trash screens. A trash screen over an opening, and only where a risk assessment says the access is safe.
• Vegetated and engineered channels. Swales, grassy channels and rills.
• Open water storage. Basins, ponds and field corners set aside to hold flood water.
• Infiltration features. Soakaways, gravel trenches and porous paving, but surface work only, such as sweeping and weeding.
• Rain gardens and woody dams. Including small embankments and overflow structures inside a sustainable drainage scheme, and the leaky dams used in natural flood management schemes.
• Earth embankment surfaces. Grass and turf protection, and minor levelling of the crest.
• Flow control structures. A weir or an orifice, subject to the limits on modification below.
• Road gullies. Surface cleansing only, which is the point where community work meets the everyday problem of keeping surface water drains clear.
• Ancillary items. Life-saving equipment, fences, gates and signs linked to flood assets.

The exclusions are just as specific. Anything underground that needs confined-space entry is out, as are geocellular and tank storage, pitched green roofs, motorway and A-road trunk drainage, anything on or beside railway land, reservoirs, and coastal defences. Coastal work is left to the coastal authorities and the guidance does not cover it.

What is off-limits to volunteers?

Four classes of activity are excluded outright on health and safety grounds: work in subsurface or confined structures, such as clearing a culvert or an underground tank; work on a structure while it is operating, which rules out raking a trash screen during a storm; anything needing specialist training or equipment, such as major desilting, large embankment repairs or reinstating pipework; and lone working of any kind.

The CIRIA guidance adds practical limits on top. Volunteers should not stand or move in water deeper than about half a metre, should carry a wading stick where the bed is uneven or the water is not clear, and should never work in a watercourse that is in flood. Chainsaws are for people with a current qualification, not for whoever happens to own one.

On rehabilitation work the rule is blunter still: a group should not carry out maintenance that changes the asset, and large-scale desilting or raising an embankment goes to a contractor or the authority every time.

There is a middle band. Restoring an embankment profile by filling settlement hollows and rutting, installing coir rolls to hold a bank toe, and planting near a channel are all things a group can do, provided the authority has been consulted first, the work will not reduce the channel's capacity, and a risk assessment says it is safe.

Who still carries the legal duty?

Nothing in C821 moves a legal responsibility. Statutory duties stay with the risk management authorities and with landowners, and the CIRIA guidance is explicit that authorities must not use it to press a community into taking work on.

That matters because the ownership picture is fragmented. A single village stream can pass from a main river maintained by the Environment Agency to an ordinary watercourse overseen by the lead local flood authority, through land where the duty sits with the riparian owner under the Land Drainage Act 1991, and past an internal drainage board district with its own byelaws. Those roles are set by the Flood and Water Management Act 2010, and we have set out the full picture of who is responsible for managing flood risk in England separately. Before a group touches anything, it needs to know which of them owns the length in front of it.

Many of those bodies hold permissive powers rather than duties, which means they may act but are not obliged to.

Do volunteers need a permit or consent?

For routine work on smaller assets that are not main river, a formal permit is often not required, but the landowner's agreement always is. Five checks settle it.

1. Establish who owns the asset and the land the group will work from, using Land Registry records and, for newer estates, the planning documents on the council's portal. The Environment Agency's guidance on owning a watercourse is the plainest summary of what that ownership brings with it.
2. Get the landowner's written permission, and renew it each time the group returns.
3. Ask the lead local flood authority whether the work needs ordinary watercourse consent, and the Environment Agency whether it needs a flood risk activity permit on a main river or a high-risk asset.
4. Check whether a lawful development certificate is needed from the planning authority. That applies to rehabilitation work rather than to routine clearance.
5. Confirm the timing against the wildlife constraints below before fixing a date.

C821 also encourages groups to ask for proportionate paperwork: a simplified proforma rather than a full application, and a licence covering several years where the same work repeats annually. C821b includes an Environment Agency channel-maintenance consent form as a worked example for authorities to copy.

Insurance and liability: where does a group stand?

There is no statutory answer, so cover has to be arranged by the group. C821 says plainly that nothing in current policy or guidance settles who is liable when volunteer maintenance causes damage, injury or flooding, which makes this the weakest part of the whole picture.

Three risks need covering: injury to a volunteer, loss or injury to a third party caused by the group's work or advice, and loss or damage to the group's own equipment. Cover usually comes by one of two routes. A group can be treated as an agent of another body, most often the parish council, and sit under its policy, though not every body will agree to that. Or it can insure itself, commonly through The Conservation Volunteers scheme, which most of the groups surveyed had used.

Read the exclusions before relying on either: volunteer policies are frequently limited to hand tools, which is why so many groups bring in a qualified local contractor for chainsaw work instead of buying their own.

The Martock group in Somerset holds public liability cover paid for by the parish council, extending beyond the parish where the group acts on its behalf with the landowner's permission, and takes time-stamped photographs of the assets it touches in case a claim is ever made.

How do you set up a community maintenance group?

Agree what the group is for, choose a legal structure, write a constitution, get the parish council behind you, and map who is responsible for each asset before touching any of them. CIRIA C821a sets that order out for groups starting from nothing, and it is worth following, because most of the difficulties groups report — permits, insurance, landowner access — get easier once the group has a name and a constitution.

1. Agree what the group is for. Maintenance is rarely the only aim; awareness, a community flood plan and lobbying for a scheme often sit alongside it.
2. Choose a structure. An informal group is quick to start but struggles to get insured or funded. An unincorporated association with a written constitution is enough for most, and gives the group a bank account and access to grants.
3. Write the constitution. Name and status, objectives, membership, meetings, committee roles, finances, amendments and dissolution.
4. Fill the roles. Chair, secretary, treasurer, a communications lead, and task-specific officers for particular assets.
5. Get the parish or town council behind you. Formal endorsement makes funding applications far easier.
6. Map who is responsible for what. Contact each authority, arrange a joint site walkover, and write down what each one does and does not do on your stretch.
7. Put the relationship in writing. A memorandum of understanding or terms of reference with the authority, naming contacts and covering how the group escalates anything beyond its scope. On the Exe Estuary, one such agreement covers residents closing flood gates when a flood warning is issued.
8. Start by watching. Observe and monitor first, so the maintenance you plan is the maintenance the assets actually need.

Most groups are small. The survey found them typically 5 to 20 people, occasionally up to 35, with 2 to 20 turning out on a given work day, and mostly retired. Some work ad hoc; the more established run 20 or more activity days a year.

When can the work be done without breaking wildlife law?

Timing is not a courtesy. Protected species are covered by the Wildlife and Countryside Act 1981, and the penalties are real: disturbing a pond that holds great crested newts can bring a fine of up to £5,000 an offence and a prison sentence of up to six months, with the vehicle used to commit it liable to forfeiture.

• Nesting birds. Every wild bird is protected. Do not remove emergent vegetation, shrubs or trees during the nesting season, which for most species runs through spring and summer.
• Water voles. Work in vole habitat in March and April, before the young are born, or in August and September when numbers peak. Cut no more than about a third of the bankside vegetation in a year.
• Great crested newts. Breeding runs roughly from February to July. Newts are easily confused with unprotected species, so stop work and take advice if any turn up.
• Invasive species. Take the regulator's advice before cutting or moving them, and clean tools and boots afterwards.
• Burrowing animals. Note burrows in embankments and basin slopes when you survey, and ask the regulator how to deal with them rather than acting.

Survey the site before the first work party: local records, the MAGIC mapping service and the regulator's local office will usually tell you what is present, and where the picture is unclear an ecologist's note is a good deal cheaper than a prosecution.

What happens when the Environment Agency stops maintaining a defence?

The Agency withdraws maintenance where the cost of keeping an asset going is judged to outweigh the benefit it delivers. Anyone affected is written to, told what is stopping and why, given the asset's current condition and usually at least six months' notice, and there is a right to challenge both the decision itself and the consultation that led to it.

Among the options the guidance offers to the people left behind by that decision is setting up a community partnership or neighbourly arrangement with others who benefit from the asset. Community maintenance is not a policy aspiration in the abstract; it is one of the answers the Environment Agency gives when it stops mowing an embankment.

The same pressure shows up in the national figures, where the gap between what has been built and what is being kept in good order is the part that matters to anyone living behind a defence.

We have written separately about what a below standard flood defence condition rating actually means, about what the National Audit Office found when it examined the capital programme, and about the 2026 FCERM funding reforms that push harder towards partnership contributions, and about the £1.4bn allocated for 2026/27. Read together with more intense rainfall, they explain why CIRIA C821 exists now rather than a decade ago.

Where community maintenance ends and professional assessment begins

A well-run flood group changes what a catchment knows about itself. Level records, dated photographs of flood extent, and trash lines marked shortly after a flood are exactly the observations hydraulic models are short of, and authorities will take them.

What a group cannot do is answer the questions a planning authority asks. Whether a site's levels work, whether a scheme displaces water onto a neighbour, whether a defence still performs to the standard it was built for and what residual flood risk is left behind it: those need survey, modelling and a chartered opinion.

If your group's monitoring has turned up a drainage problem that needs designing rather than clearing, we can prepare a surface water drainage strategy for planning. And if a development is proposed on the ground your group has spent years watching, talk to our chartered flood risk consultants before the application is decided rather than after.