Enviroment Agency: the case for the modernisation of the Northmoor Weir

Managing the Thames

We are responsible for managing the freshwater section of the River Thames, from St John’s Lock in Wiltshire to Teddington Lock in West London. We manage the natural environment of the river, while also working to reduce the risk of flooding to people and property along its banks. We also maintain the river for navigation purposes, allowing boats to pass along its length.

Northmoor Weir

The weir at Northmoor Lock dates back several centuries. It retains a head of water upstream, creating enough depth to allow boats to navigate the river. After the 2007 floods an assessment concluded that the weir at Northmoor should no longer be operated manually due to the high risk of injury to operators.

With an inoperable weir we would have less control over water levels, and flood risk to the local area would increase.

Removing the weir permanently would prevent boats from travelling along the river, and would also adversely affect the biodiversity and natural appearance of the river.We will therefore replace this weir with motorised gates starting in April 2010. This will allow us to operate the weir safely and effectively.

Northmoor is one of five Thames area weirs to be replaced by October 2011.

Consultation

We initially consulted on replacement options in summer 2009. We have made some changes to our design based on responses received at that time. We have produced an Environmental Report which will be on our website www.environment-agency.gov.uk/paddlerymer  from 3 March. We would welcome your comments on the report by 24 March.

Important elements of the work include:

•  replacing the weir in two halves – one half in 2010 summer season, the other half in 2011; 
•  building a temporary dam around each half of the weir at the start of each summer season;
•  some minor coppicing of trees on the river bank to allow access;
•  providing temporary access to the lock island until completion in 2011;
•  reconstructing the concrete base of the weir; 
•  installing new piers and motorised weir gates;
•  stone cladding parts of the existing abutments;
•  providing a new access walkway with new handrails.  

Some of this work will require the use of cranes mounted on barges.
The construction work will take place between 8am and 6pm Monday to Friday, and 8am to 1pm Saturday.  No work will take place on Sundays or public holidays.

Temporary disruption and managing the risk of flooding 
There will be a temporary increase in noise and dust because of the construction work. This may affect the lock keeper’s cottage and boaters using the lock and moorings. We will ensure that disruption is kept to a minimum.
Construction vehicles will use the access road from Badswell Lane. Access roads will be kept free from mud and construction material at all times and we will have measures in place to minimise dust.
There will be a temporary increase in traffic through the village, but the number of vehicles is unlikely to be high. To minimise the impact on the local community, we will employ the following management measures:  

•  deliveries will be co-ordinated to impact as little as possible on the local traffic;
•  people will supervise the movement of construction vehicles and machinery;
•  speed limits will be enforced for site vehicles on private land; 
•  modern machinery will be used to minimise noise and disturbance. 

During the work we will create a temporary dam to allow us to replace the weir. If high levels of rain at this time make flooding of properties likely, we will remove part of the dam to allow potential flood water to flow downstream. 
We will also use our knowledge of past floods to provide protection for properties at risk of flooding.
If the river rises above the level of the banks, we will put warning signs in place for boaters and people using the Thames Path.

Benefits for the future
Replacing the weir will protect the local community from that increased flood risk.
It will enable us to operate the weir safely and effectively for many years to come, to manage river levels and ensure the smooth passage of boat  traffic along the Thames.

For more information contact:
Paul Fraser, Project Manager 
paul.fraser@environment-agency.gov.uk
Tel: 08708 506506