Pages 28 to 33. Future Tidal Barrier at Boston. The following information was obtained at an Environment Agency exhibition in the town, 11 November 2014.
The barrier will be located across the River Witham, a little downstream of the access lock into the Black Sluice Navigation, thereby managing the tide in the Witham and making access to the Black Sluice available for a longer period each day. This will be more important when the Fens Waterways Link, via the Black Sluice, is completed to the Nene near Peterborough, via the rivers Welland and Glen - making a navigable circular route of the fens waterways.
Although the new barrier will be an aid to inland navigation its primary function is to prevent flooding in Boston, the town suffering greatly during the east coast tidal surge in December 2013 when over 800 properties were extensively damaged.
will rise up to block the water flow, and sink down to allow the natural
flow of the tides, plus passage of boats through it.
A bird's-eye view of the planned barrier, raised up across the River Witham. Downstream is on the right.
From inland the Witham is already controlled by the Grand Sluice and its lock, on the western edge of Boston, holding the levels of freshwater. The stretch between the Grand Sluice and the planned barrier passes through the centre of the town and is currently fully tidal, therefore resulting in extensive, some say "unsightly", mud-banks, during much of the day. Therefore, many factors have to be considered when deciding on the levels at which the water will be held between the two control points, and at what times - boats going to/from the North Sea via The Wash and the lower Witham, those to/from the Black Sluice lock, fish habitats, high river flows from inland, the positive effect on the appearance of Boston's riverside areas, and the crucial flood-prevention in Boston and surrounding areas.
No definite decisions have yet been made about water-level management but it's likely that the new barrier will be closed during daylight hours. The morning high tide will flow up to the Grand Sluice, as it does now, but its waters will be captured by the barrier when the levels have fallen to the desired level. On the rising evening tide, when the levels are equal on both sides, the barrier would be opened. The high and low tide would then occur naturally through the town overnight. However, the barrier would not operate during high river flows, so allowing maximum discharge of freshwater out to the North Sea. No decision has yet been made on the levels which will be held in the freshwater Witham above the Grand Sluice. It may also be that annually, from 1 November to 1 April, the barrier will only operate when a tidal surge is predicted.
Nov 2014 - late 2015. Preliminary designs and the preparation of a Transport and Works Act Order (TWOA).
Late 2015 - spring 2017. TWOA application considered by the Secretary of State.
Summer 2017 - late 2019. Multi-functional Boston Barrier and associated works completed.
The "associated works" will be raising the lowest sections of the Witham's banks upstream of the new Boston Barrier.
An Environment Agency video, using a 3D-printed model and a graphics mock-up, shows the planned enviroment of the barrier and a boat passing through. tinyurl.com/omytyk5
The barrier closed, with raised river banks.
We wait to see - but the prevention of tidal-flooding aspect of the scheme will ensure something is done.