Blue Ribbon Network policies and water space

The Blue Ribbon Network is the London Plan's name for the capital's water space and the land beside it, covering the Thames, the canals, the docks, the tributary rivers and the reservoirs. Development on the water or on a site that fronts it is judged against policies that treat the water as infrastructure rather than as a view, and the practical consequence for the blue ribbon network in London is a priority for water dependent uses and a set of expectations about frontage, ecology and public access.

What the network covers

The designation is deliberately broad. It takes in the tidal Thames and its foreshore, the canal network, the enclosed docks, the River Lea and the other tributaries, and the open water of reservoirs and large ponds.

It also includes the land alongside, because the way a riverside building meets the water determines whether the water reads as a public asset or as a service yard. So a scheme set back 20 m from a canal is still assessed against these policies.

Different parts of the network have different managers, and that matters more than the policy wording in day to day terms. The tidal Thames has a harbour authority, the canals and many docks have a waterway authority that is also the landowner, and the rivers bring the Environment Agency in as a flood risk and water quality body.

Water dependent uses and the priority they get

The structural principle is that uses which need the water come first. A boatyard, a passenger pier, a moorings basin, a water sports centre, a freight wharf and a lock keeper's facility can only exist on the water, and once that space is lost it is not recreated.

So the policy sequence runs from water dependent uses, through uses that benefit from a waterside location and contribute to it, down to uses that merely happen to be beside the water. A residential block with a blank ground floor facing a canal is at the bottom of that hierarchy and will be asked to change.

That priority bites hardest on marine support space. Boatyards and slipways occupy unglamorous sites with high land values beside them, and an application to replace one will need to show that the facility is not needed or cannot be retained, in much the same way the wharf safeguarding test works. Our note on industrial land in London and no net loss sets out the equivalent evidence standard for employment land.

Development alongside canals and rivers

The recurring design issues are the same on almost every waterside site.

• Active frontage at the water's edge, with entrances, windows and uses that face the water rather than turning their backs on it.
• Servicing, bin stores and plant kept away from the water frontage, which is where they usually end up on a first draft.
• Height and massing that does not enclose a narrow canal corridor or overshadow the towpath for most of the day.
• Public access along the frontage, continuous where possible and connected to the wider network at both ends.
• Retention of historic structures, including walls, steps, bollards, cranes and mooring rings, which are frequently the only surviving evidence of the water's working past.

Overshadowing of a towpath is worth modelling early. A continuous wall of building on the south side of an east to west canal removes the sun from the towpath for the whole winter, and an Overshadowing Study showing the effect at the equinox and midwinter is the evidence that shapes the massing rather than defending it later.

Culverting is resisted and de-culverting encouraged. Where an application affects a watercourse, treat opening it up as the starting assumption and justify anything else.

Moorings and residential boats

Moorings raise a planning question that catches people out. Where a vessel is permanently moored and used as a dwelling, the use of the water space can amount to a material change of use requiring planning permission, even though the boat itself is not a building.

The tests are factual. Permanence of the mooring, the degree of physical connection to the bank through services and access, whether the vessel moves, and whether the space is used as residential accommodation rather than as a berth for a cruising boat.

Residential moorings also need the practical infrastructure, and that is where applications fail. Each berth needs a safe access and gangway, refuse and recycling storage within a reasonable drag distance, water and electricity, a pump out or holding tank arrangement, parking or a clear statement that there is none, and a postal address. Set those out berth by berth rather than in general terms.

Consent from the harbour or waterway authority is separate from planning permission and neither substitutes for the other. You need both, and that body's view on berth spacing and access will usually be decisive on layout.

Ecology and water quality

Water space supports species that are easy to miss in a standard appraisal. Bats commute along canal corridors because the corridor is dark and full of insects, and lighting a towpath to urban street standards severs that route.

So lighting design is an ecology matter on these sites. A lighting scheme with a defined dark corridor, warm colour temperature, shielded optics and no spill onto the water surface is the usual answer, and a Lighting Assessment against the relevant obtrusive light guidance is the document that evidences it.

Bank treatment is the second issue. Vertical sheet piling supports almost nothing, while a reprofiled bank, a floating reedbed or a shelf at water level supports a good deal. Those measures also score in the biodiversity metric, so the ecology and the policy pull in the same direction. A Preliminary Ecological Appraisal by an ecologist should cover the aquatic margin rather than stopping at the top of the bank.

Water quality matters during construction as much as in operation. Expect conditions on silt management, concrete washout and fuel storage near the water, and a construction method statement that deals with works over or adjacent to the channel.

Flood risk in a waterside scheme

Being beside water does not automatically put a site in a high flood risk zone, and being behind a defence does not take it out of one. The Flood Risk Assessment has to deal with the source that actually applies, which on the tidal Thames is tidal flooding behind a defence and on a canal is usually a breach of the canal itself.

Canal breach is the scenario most often missed. A canal held above the surrounding ground level is a raised body of water, and a breach assessment for development below it is a reasonable thing for a lead local flood authority to ask for.

Finished floor levels, safe access and the design life of the development are then the same questions as on any defended site.

Who to consult before you design

Pre-application engagement on a waterside site is worth more than almost anywhere else, because the constraints come from bodies that are not the planning authority.

Speak to the harbour or waterway authority about berthing, access and works over water. Speak to the Environment Agency about flood risk, water quality and any permit for works in or near the channel. Speak to the authority responsible for the towpath about access, surfacing and lighting. And where a passenger pier or freight use is proposed, the transport body with responsibility for river services will have a view on capacity and on pier spacing.

Get those positions in writing before the layout is fixed. A waterside scheme redesigned after an objection from the waterway authority is an expensive lesson in sequencing.

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