Dave Cross has been trawling the depths of the Ouseburn River to find out why the Ouseburn Barrage has been out of use for most of its life, and why we should expect to see it closed much more often in the future.

In 2004, Newcastle City Council applied to the Secretary of State for Transport, Department for Communities and Local Government, for an Order which “would authorise Newcastle City Council to construct a tidal barrage with moveable lock gates across the Ouseburn and to execute ancillary works, including dredging of the upstream Ouseburn.”

This was followed by an extensive public enquiry, which heard a great deal of evidence, much of it in opposition to the  barrage. Ultimately, the Order was granted in 2007, works commenced, and the barrage was completed and formally opened (or should that be ‘shut’?) in 2009.

Ouseburn Barrage closed

A barrage of enquiries

Since then, it has been open more than closed, which has led to much speculation and many enquiries asking:

  • Why has the barrage been open for most of the past seven years?
  • Was it a useful allocation of public funding?
  • Does it not keep out high tides?
  • Is it broken again?
  • What happens to the wildlife in the tidal Ouseburn River?
  • What is the barrage for?

We can now add another question to the list: 

  • Why will the Barrage be closing this month?

The barrage is constructed as a pair of lock gates, so that vessels can pass through one gate and close it behind them, then allow the water levels to equalise at the second gate before opening it and sailing through it. Of course, this procedure only works when the tide in the River Tyne is high enough to float the vessel. The mechanism won’t operate if the tidal level is too low. Due to the publicity around barrages elsewhere which exist to protect land against flooding, such as in the Thames Estuary, many people have assumed that the Ouseburn Barrage would do the same. But not only was it not intended to protect against incoming rising water from the River Tyne, it was specifically designed to permit the high waters of a normal ‘spring tide’ to flow over the weir alongside the barrage bringing sea water into the Ouseburn River basin as the tide comes into the Tyne from the North Sea.

Back in 2004, the City Council set out its reasons for constructing the barrage:

  • to contribute to the delivery of local and regional policy and strategic objectives;
  • to significantly contribute to achieving the regeneration objectives of the Lower Ouseburn Valley area as set out in the Ouseburn Regeneration Strategy;
  • to solve the problems of a poor quality estuary environment at low-tide including visual appearance, unpleasant odours and access to the river;
  • to improve navigation by recreational vessels upstream of the barrage by retaining the river at a permanent level just below high tide;
  • to increase developer confidence by increasing the attractiveness of the degraded riparian brownfield sites currently blighting the river water frontage;
  • to enhance the river environment for local people, visitors and wildlife including protected species; and
  • to promote wider economic benefits in the valley by encouraging greater investment and visitor interest.

 Adding that the construction of the barrage would “act as a catalyst for regeneration and to improve the local environment in the Lower Ouseburn Valley”.

It was an innovative and unique design. Not only do the lock gates slide up and down, above the height of most vessels (providing a higher clearance than is available under the nearby Lower Glasshouse Bridge), but an electronic microcontroller regulates the operation, determining what action to take using ultrasonic detectors which record the water levels on both sides of the lock gates. Canal locks which exist into tidal waters are not unusual (e.g. the Caledonian Canal at Forth William and Inverness) but the electronic regulation and the mechanical interlocking is unique,

 

It’s not broken! It’s just out of use

It was dogged with problems in the early years, with a fail-safe lock-out arrangement which meant that (more often than not) it would default into a non-operational state, but in recent years it has been held out of action with good reason. There has been a lot of work to do in the river which is only possible when the water level is low. In the past year, the barrage has been kept open except for the weekend of the Ouseburn Festival and for a special visit due to:

  • The housing being developed on the east bank has required rainwater run-offs to be built under ground and entering the Ouseburn through conduits ending in the river wall;
  • the large stone steps leading down into the water near the Tyne Pub had slipped away from their alignment and were unsafe requiring repairs;
  • lack of maintenance to the river retaining wall for such a long time required a full survey of the wall at low tide;
  • the potential residential development on the west bank at ‘Lower Steenberg’ required a more careful examination of the underground rainwater ducting and works and the development of plans to reinforce the river retaining wall.
  • Other tasks included breaking up a large block in the riverbed which obstructed the navigation channel near the Tyne pub, to allow repairs to some of the floating wildlife refuges, and to assist the extensive works to repair the Ouseburn Culvert, particularly the box section between the current exit of the culvert and the former exit.

In addition to all the repairs and remedial work, there is the question mark over the ability of the barrage to discharge heavy rainwater adequately, which during the intense rains of 2012 it did not. During intense rainfall, it enters ‘flood alleviation mode’ and the gates will automatically open and close in steps to regulate the flow into the Tyne. Since then, changes were made to the mechanism and to the software (the code was completely re-written), but until we experience another period of equally intense rainfall, it will remain in ‘test mode’.

The impact of high volumes of rainwater on top of the impounded river is quite different from the impact on a tidal river, and the usual calculations for river flow (Mannings Equation for those interested in further reseach) don’t help us to calculate the flow of rainwater flowing downstream when simultaneously tidal seawater is flowing upstream. So until this unique design, and its operational procedures have been re-tested under stress conditions, then there remains a risk of flooding to properties, which is of course the most persuasive argument for caution in re-introducing the barrage into action. Excessively high water also puts boat moorings at great risk. Some moorings have already failed, one boat was sunk and another broke away. One rose up and floated over the top on top of the retaining wall and was left stranded there when the water level receded.

When the barrage was designed just ten years ago, the intense levels of rainfall over a short period of time that are experienced these days were never anticipated. e.g. five occurrences of an event deemed to occur “once in a hundred years” in 6 months. It’s a local example of the impact of actual climate change.

 

Muddy waters

We have found that when the barrage is closed for even just a few months, the build up of silt in the river bed becomes problematical. It reduces the navigation depth, and reduces the channel area available for discharging rainwater. It also smells dreadful. We had hoped that by leaving the river tidal for a few weeks, then the ebb and flow of sea water would wash some of it out, but it is now quite clear that a few days of heavy rain does a lot more to remove silt than a few weeks of tidal flow. Consequently, it is being proposed that the river is left tidal for about a quarter of the year to assist in controlling the build up of silt. There does remain, though, a large ‘hill’ of silt at the foot of the Cluny slipway, and which is suspected of containing contaminants and as a consequence of that suspicion, it cannot be disposed of cheaply.

Finally, some people noticed that once the barrage was opened following its closure for a few weeks last summer, that water was escaping from the foundations of the John Dobson built 36 Lime Street. That building was designed to have its foundations submerged by the tide twice a day, and water doesn’t escape like that when the tide falls, so questions were being asked about the effect of prolonged submersion of the foundations. Impounding the river for a sustained period appears to silt up the apertures and it doesn’t drain properly until a good few tides ‘push and pull’ at the accumulated silt to clear out the apertures. Sadly, inspection access under the building cannot be found, and so the impact is hard to assess and mitigation techniques are only a guess.

 

Life on the river

While the river remains tidal, there is plenty of food for those whose life depends on scouring the river bed for small shrimp, eels or fish. The swans come upstream ahead of every tide to feed on whatever they find. The most spectacular residents while the river has been tidal have surely been the kingfishers and otters. It’s not clear how many of these species will continue to find the Ouseburn a useful habitat and source of food when it is impounded again by the barrage.

 

Closing the Barrage

The Ouseburn Barrage will be brought back into operation this autumn, maintaining a high water level, which will vary only when it rises though heavy rainfall upstream or high tides back-filling the river basin from the Tyne.

The issues around the use and condition of the lower Ouseburn river and the Barrage are overseen by the Ouseburn River Users’ Group who will be watching the next stage with interest. This group include Newcastle City Council’s Chief Engineer, the Port of Tyne Authority, the Environment Agency, Newcastle Motorboat Association, Royal Yachting Association and some other boat users and owners of adjoining properties.

Dave Cross

Ouseburn Trust Trustee and Chair of the River Users' Group