Thames Barrier visit and return boat trip

Thames Barrier Information Centre Visit and Talk, with return boat-trip and an exclusive one-and-a-half hour introduction, on Saturday 21 July, departing Westminster Pier.

From the announcement in the Spring Newsletter:

July is the heart of summer, so why not join us on a very summery day out? Two events only rarely available to the general public have been combined for the ANS:

The first is the rare chance to get off the Thames Services groups excursion boat at the Thames Barrier pier; only once a day, on 9 weekends a year, does a boat stop there to let passengers off. The Barrier is an astonishing construction, and best appreciated from a boat; and there is so much to see along the river, including pubs frequented by Samuel Pepys and Oscar Wilde, squeezed between new buildings rising up at an astonishing rate.

The second is a talk exclusively for the ANS at the newly renovated Information Centre, about the Barrier, the history of the Thames, the risk of flooding in London, and the environment and wild life of the river. The exhibition has been updated, and the cafe and terrace have been enlarged, and there is more space for group talks, and of course it offers a unique view of the Barrier (which, unfortunately, no-one is allowed onto).

Did you know that the Barrier was built by a consortium including a Dutch construction firm (BAM)? Or that it was only expected to be used 2 or 3 times a year, but it is already averaging 6 to 7? In the wet winter of 2013/14 alone it was opened and closed 50 times, thereby preventing London from both fluvial and tidal flooding – maybe you own a house which was saved from flooding by the barrier! This and many other interesting facts will be touched upon in the talk.

Our boat will depart from Westminster Pier around 10.30, and arrive at the Information Centre around 12. You can either have lunch in the cafe, which will offer a simple menu, or bring your own lunch which can be eaten on the picnic tables outside or the grass banks of the Thames. If you would like to eat in the cafe, it is advisable to book your choice ahead of arrival. If you indicate this on your form, a menu will be forwarded to you as soon as it is available so you can be certain your choice is in stock.

Apart from the talk, there is plenty of time to look at the Barrier, and have a wander through the Barrier Park behind the centre. Our boat will come and pick us up again at 3pm. On the way back it will stop at Greenwich and St Katherine’s Dock, for those who fancy adding some more interest to the trip. We should be back in Westminster by about 4.30. The commentary on board is not intrusive, but will keep you interested all the way.

 

From the report in the Autumn Newsletter:

Visit to the Thames Barrier, by riverboat from Westminster

Report, by Alan Denney, of the visit on Saturday 21 July

Our riverboat trip started at Westminster Pier and our group of 26, led by Evelien and John, headed for the upper deck of the ferry to enjoy the seemingly everlasting sunshine of London. Our trip took us downriver enlivened by a commentary from one of the crew members given in his own inimitable East End way, with the appropriate laconic style and wry humour.

We arrived at the Thames Barrier and were greeted by our guide Pam Hildrew who allowed time for the essential (and tasty) cup of coffee. Pam then talked to us about the Environment Agency and their many roles including flood defence and their mission to inform and educate about their role. She explained that the Romans built Londinium on what is now Ludgate Hill but London spread onto much lower ground where there is an ever-present flood risk, which is currently a risk to at least 1.3 million people, not to mention the property, infrastructure and national economy. She mentioned floods in Pepys time, again in 1928 and lastly in 1953, from which the need for the barrier originates.

The barrier was completed in 1982 and was first used in 1983 even before its official opening by the Queen. Since then it has been closed to prevent London flooding 183 times, including five times last winter. What necessitates closure is the combination of naturally high and predictable tides combined with a surge which comes from low atmospheric pressure. Closure is planned about 36 hours ahead of time using complex forecasting and prediction methods.

The barrier is part of an extensive system of barriers (including 35 major gates and 100 minor gates) as well as passive defences to protect the whole of the tidal Thames and Thames Estuary and the whole system is co-ordinated between all emergency agencies. This is a significant change from 1953 when there was no prediction of the flooding which devastated Essex and the Thames Estuary and much of the Netherlands, with no warning.

The brief for the barrier was developed when the docks were open in the East End with the daily movement of hundreds of large ships. This defined the need for the gates to be sub-surface, as well as setting the minimum width for the central channels of the barrier. Pam explained that the main gates are ‘rising sector gates’; they sit flush with the river bed, are curved in section and are raised by push-pull action from hydraulic cylinders moving a beam which rotates the circular plates to which the gates are attached.

The concept came to Charles Draper, one of the draughtsmen at the designers, Rendal Palmer and Tritton, when he was using a simple type of tap. Simplicity and robustness were built into the concept. Each of the large 61m wide gates weighs 3,700 tonnes. The shallower, less navigable channels close to each bank are closed with ‘falling radial gates’.

The gates are hollow and are flooded. Given that the system must not fail there is multiplication of systems, in hydraulics, instrumentation and power generation. The word used was ‘resilience’. There are 90 staff, including 40 engineers. Twelve are required to close both this barrier and the companion one, which seals Barking Creek. However an important principle in the operation is that the decision to close is taken by one person working from the information given by his team.

Operational security, maintenance and future-proofing are part of the mission. Every two months there is an extensive co-ordination check and once a year there is a grand closure of the entire system, which is advertised on the web site for the public to witness (this year it is on 23rd September). Maintenance in the salt water environment is continuous, apart from the stainless steel cladding, which has never needed to be touched since installation.

Pam showed us the model of the operation of the rising-sector gates and we then watched a fascinating ‘walk-through’ video of the site. The height from the top of the stainless steel housings for the hydraulics to the bottom of the foundations, with the parked gates, and tunnels for the services, was equivalent to the height of Nelson’s column. We fully appreciated that from the amount of walking up and down stairs involved in the virtual tour! We then looked at the fascinating exhibition with displays and videos about the Thames and the construction of the barrier. We went outside for a walk to see the barrier close-up, with the bright sunshine reflecting off the stainless steel. In ideal conditions we could appreciate the iconic architectural form of the piers and housings for the drive mechanisms, which was derived from the bows of a ship.

We had time for lunch and a group photograph and at 3pm our ferry turned up to return us to Westminster, again in bright sunshine and again with an amusing commentary.

Our thanks go to Evelien for organising such an educational and interesting tour. It was a great day out.