By Trevor Timpson
The first of the sluice gates has been lifted into place
Some tidal creeks in east London are in the middle of changes that will see them become a major freight route once more.
Perhaps, as enthusiasts hope, they will finally become a "new Amsterdam".
They are the Bow Back Rivers and they lie to the east of the River Lea as it approaches Bow Creek and the Thames.
North of Stratford High Street, most of the Bow Back Rivers have already been enveloped by the huge construction site that is the Olympic Park, and it is hard to see them because their waterside paths have been blocked off.
Further south, it is all very much quieter. The factories once served by fleets of barges and lighters have mostly gone. Where streets of houses line the water, they turn their backs on it.
Vessels used to work up on the tide, then settle on the mud to unload and load.
Now, at low tide, the mud and the rubbish have the Bow Back Rivers to themselves.
"If you go there now at low tide you'll see a 15-foot drop into a patch of mud covered with rusty motor cycles and shopping trolleys," says Colin Edwards, an officer of the Inland Waterways Association's London Region.
But the channels are destined to carry up to 1.75 million tonnes of construction materials to the Olympic sites.
British Waterways says 350-tonne barges using a new £18.9m lock will save local roads from tens of thousands of lorry journeys off local roads.
The Prescott Channel (above) was built as a flood relief in the 1930s
Sir William Prescott (inset) chaired the Lee Conservancy Board
Now the channel will be a major Olympic supply route
Two new wharves will be constructed on the Bow Back Rivers within the Olympic Park, and the vessels will also be unloaded by crane.
The first of the 21-tonne sluice gates has now been lifted into position next to the lock site, on the Prescott Channel near Bromley-by-Bow. Later this month the 17-tonne lock gates will also be lifted in.
For British Waterways it is the fulfilment of hopes which originated before London got the Olympics - and whose long-term effects are meant to last long after 2012.
"It's been fantastically interesting," says senior project manager Mark Stephens. "I've worked on it for four years now since the conceptual stage - it's been a really great thing to be involved with."
He says the lock will be ready for the first barges in October.
North of the lock, the water level in the Bow Back Rivers will be constant and not tidal - changing their nature and keeping the mud out of sight.
In the 1930s the Lee Conservancy Board put in water-control measures - including the quarter-mile long Prescott Channel, named after the board's head, Sir William Prescott, to allow flood water to be diverted through the area.
LEA OR LEE?
"Lea" is the old name for the river and for its valley
It is usually spelt "Lee" when it refers to the Lee Navigation, canalised for boat traffic
But sluices meant to control the Prescott Channel were no longer needed after mills whose wheels were turned by the tide ceased operation.
The sluices stuck and the incoming tide poured over them, and local children swimming in the channel dubbed the place "the waterfall".
Eventually, the sluices were taken out. Locks between the Bow Back Rivers and the Lee Navigation were left unused and blocked.
But the idea that the area could be a sort of Venice of east London had already been born.
"You will see the elite in blazers and straw hats, pulling their skiffs up and down," enthused the Stratford Express in 1933.
"Lots of people who live there haven't realised what a beautiful place is on their doorstep," says Andrew Mawson, who has worked in promoting enterprises in the area for many years.
Drive the economy
A crossbench peer, Andrew Mawson said in the House of Lords in January that the Olympics had given extra impetus to the Water City ideal.
"The Olympics have the potential to act as a catalyst to lift the game on the £20bn of development that will take place down the valley over the next 20 years," he said.
He told peers he had long hoped that they could "turn round the fortunes of the Lower Lea Valley and build what we called the Water City - a practical vision that would use many miles of waterways in the Lower Lea Valley to lift land values and once again drive the economy of east London".
Non-commercial vessels will also benefit from the lock project and the constant water level, says Colin Edwards of the Inland Waterways Association.
"The impounded level is a blessing because previously you had to have a set of tide tables to know you had enough water to float and not enough to stop you getting under the bridges," he said.
In the long run, British Waterways hopes to see "a new East End Amsterdam which is fully accessible for boats and people and incorporates wildlife habitats and high quality waterside parkland."
One local estate agent was quoted as saying a canal view would add £15,000 to the price of a third- or fourth-floor property in the area.
For others, though they welcome the Prescott Lock project, doubts remain.
Near the Lock is the House Mill - one of the biggest tide-powered mills ever built, it ground grain for gin manufacture from the mid-18th century until 1941.
The River Lea Tidal Mill Trust is undertaking a £2,500,000 appeal to get the tide turning the mill wheels once more below the grade-one listed building - and to add turbines for the generation of electricity.
The new lock will be an advantage, says Beverley Charters of the trust - because the water needed for the mill will not run away up the Prescott Channel, as it has since the old sluice was taken out.
"If we get water going through in the right places and not up through the floor it might be superb for us".
But high spring tides already flood the floor of mill just above the wheels on two or three days a month, she says.
Incoming tide water
Surely blocking the Prescott channel and Three Mills Wall River against the incoming tide cannot make this any better?
"We have undertaken extensive modelling and the current works will have no effect on the potential for flooding," British Waterways insists.
The Environment Agency adds: "Systems are also in place so that, should we feel it necessary for the purposes of flood risk management we can direct British Waterways to operate the structures (e.g. lower the weirs and open the lock) and to restore the channel to its un-impounded state.
"We don't believe that these structures will reduce flood risk, but we are satisfied that the flood risk is not worsened."
Controlling the water level in the Bow Back Rivers has meant installing a weir on the Three Mills Wall River a couple of hundred metres above the mill.
It leaves some people wondering if enough space will be left to store incoming tide water to power the mill when it is let out.
"We really did want them to build it further up; we begged and pleaded for it to go further up," says Beverley Charters. "We believe that we're the largest tide mill in the world - and we end up with the smallest tide."
But British Waterways says the wheels will turn, and that water coming through the weir can be used to supplement the tide water.
An appeal aims to get the tide to work again beneath the House Mill.
Water in the tidal pool above the mill would drain down very quickly, says Mark Stephens. "But it would be constantly topped up by the water on the other side of the gate - which would allow you to mill throughout the low tide period."
Del Brenner, a member of the London Waterways Commission which advises Mayor Ken Livingstone, has his reservations about the Water City vision of the future.
To his way of thinking "British Waterways have taken their eye off their main role - they're not a property developer; they're a navigation authority".
Still, he says the new Prescott Lock is "a wonderful piece of engineering... I just hope it realises its full potential".
Mark Stephens, of British Waterways, says there is no doubt that it will. After the Olympic construction campaign and Stratford International station, he says, there will be the redevelopment of Stratford itself, the building of Crossrail, and a new "super-sewer" from nearby Abbey Mills to Beckton.
And if the need for big barges should ever end, the lock could be adapted to make it more suitable for small craft, he points out.
"The restored waterways could be used to carry waste and recyclates from new homes established in the area, as well as attracting increased leisure boat activity - trip boats, water taxis, floating restaurants, houseboats and visiting craft," says British Waterways.