Our work: Millbrook footbridge and tumbling bay weir

Published:: 23 June 2024

The weir at Millbrook in full flow — Millbrook weir in full flow | © National Trust/Nina Elliot-Newman

The River Wey and Godalming Navigations bring together a network of 16 locks, 13 weirs, 56 bridges, 11 mooring lines and 20 miles of towpath, along with many other structures. The tumbling bay weir and footbridge at Millbrook sit within the vast network, as just one of many parts of the navigations the National Trust looks after.

Guildford's much-loved weir

Millbrook tumbling bay weir lies in the very heart of Guildford town centre.

It is believed that there has been a weir on the site since the 12^th century, put there by mill owners to control the water levels in the pound above in order to power their mill wheels. Today, the weir plays an important role in maintaining water levels along the River Wey.

How the structure works

The tumbling bay is a fixed crest weir which allows water to tumble over from one level (or ‘pound’) to the next, giving the site its much loved rushing sound. The structure also contains a set of three sluice gates which can be raised or lowered manually to adjust water levels. A footbridge previously ran over the weir channel, linking the footpath onto an island of green space, with the towpath continuing beyond.

Water levels over the weir vary at different times of the year, from a slow trickle in summer to a constant torrent during wetter months, when up to two million litres or water per hour might cascade over the crest.

The collapse of the weir

In 2019 the structure which dates back to the early 1900s collapsed during a period of very high water. The Trust worked with Guildford Borough Council to put in an essential temporary repair to make sure that water levels could be maintained and to keep the navigations open to river users.

However, the footbridge is still closed, with a short detour in place for walkers and cyclists to rejoin the towpath at Guildford Rowing Club or the Yvonne Arnaud Theatre.

Engineering options

Since taking over sole responsibility for the site in 2023 we have been working to find a way to restore access to that part of the towpath again. We have commissioned a team of specialist local engineers to look at different solutions, including putting in a temporary bridge, replacing the weir structure, or getting to the towpath by a different route.

During 2024 engineers will be carrying out a geotechnical investigation of the banks and the land around the site to check if it is stable, and a structural survey of the old sluice gate structure of the weir, to see whether they would be safe to build against. This work can only be done at certain times of the year because of the varying water levels.

You may also see members of the team on site as they carry out a topographical study of the wider area, as well as an environmental survey and a flood risk assessment.

What happens next?

This is a complex project, and we want to find a solution that will stand the test of time.

The work of our specialist engineers will help us plan how we can restore a permanent footpath at Millbrook, so that walkers and cyclists can once again enjoy the full stretch of the towpath.