Ouse Washes Section 10 Works information page

Closes 30 Oct 2020

Opened 13 Jun 2019

Overview

The purpose of this page is to provide information on how we comply with the Reservoirs Act 1975 and how we maintain the protection from flood risk for homes and businesses along the Ouse Washes.

Click here to provide your views on the Welney Wash Road barrier work timings.

The Ouse Washes Flood Storage Reservoir, is a 90,000,000m3 flood storage reservoir located in Cambridgeshire. It is approximately 30km (19 miles) long and up to 0.8km (0.5 miles) wide providing 1,900 hectares (approximately 4,700 acres) of land between the banks. The Dutch Engineer, Sir Cornelius Vermuyden, originally created the Ouse Washes in 1653 for the purpose of storing flood water.

Earith Sluice regulates flow entering the Old Bedford River and the Ouse Washes.  Welmore Lake Sluice and pumping station maintain a defined water level in the Washes. The Ouse Washes is confined by the Middle Level Barrier Bank (Old Bedford) and the Cradge Bank (Hundred Foot River). Together these structures form the flood storage reservoir and are registered under the Reservoirs Act 1975 (the Act).

aerial view of the ouse washes floodedAerial view of the Ouse Washes flooded

The Ouse Washes is one of the largest remaining areas of lowland wet grassland in the UK and holds notable environmental value as a Site of Specific Scientific Interest (SSSI), Special Protection Area (SPA), and a Ramsar site.  It is also important from an agricultural aspect and is heavily grazed during the summer. This grazing serves a dual purpose as it facilitates the management of the Washes by controlling vegetation and maintaining the effective transfer of floodwater; it also acts as an effective technique to manage the grassland habitats providing best conditions for the vast array of bird species visiting the area.

The Ouse Washes is maintained by the Environment Agency (river, embankments and other structures), private landowners and the Hundred Foot Washes Internal Drainage Board (riparian habitat). 

A qualified civil engineer completed an inspection of the Ouse Washes in 2013 and recommended a number of Measures in the Interests of Safety under Section 10 (6) of the Act. These resulted in a project to raise the Middle Level Barrier Bank to address changes to the bank crest level caused by settlement.

Ouse Washes diagramDiagram of the Ouse Washes

There are 3 roads that cross the Ouse Washes. These roads are called wash roads and are located at Earith, Sutton Gault and Welney.  When the Ouse Washes is flooded these roads are under water.

Welney Wash Road barrier construction works (2021)

The Welney Wash Road crosses the Ouse Washes Flood Storage Reservoir and creates a low point in the Middle Level Barrier Bank. This low point increases the flood risk to the local community and the chance of a breach in the bank if water levels were to overtop it.

When the Washes is flooded and the water level on the Welney Wash Road reaches a predetermined level, Norfolk County Council highways team closes the road. When the water level rises to a higher, preset level, we have to build a temporary flood barrier across the road to stop the water spilling into Welney village. The last time we created such a barrier was in the winter 2012/13. Installing large sandbags is costly in terms of labour and waste.

 

Aerial view of the Ouse Washes and the Welney Wash Road flooded

As part of the bank raising work we are doing to comply with the Reservoirs Act, we need to provide a more robust barrier on the Welney Wash Road where it intersects the Middle Level Barrier Bank.

We have sourced a demountable barrier option that will provide the robust flood protection solution and will be bespoke to Welney. We will store and deploy it from our Ely depot.

We will build a short concrete support wall on each side of the road by Welney to join the temporary barrier. We will also build a concrete slab across the road to attach the barrier whilst it’s in use.

We will ask for permission from Norfolk County Council Highways team to close the road during that period to do this work. 

Our objectives

Our objective is to ensure we comply with our duty under the Reservoirs Act to reduce the risk of an uncontrolled breach of water from the reservoir.

The Middle Level Barrier Bank protects surrounding areas from flood water stored in the reservoir. Our recent assessment of the bank height shows that flood water could overtop the bank at isolated locations in the equivalent of a 1% probability event. Overtopping could lead to erosion and subsequent collapse of the bank. Under the Act, the Middle Level Barrier Bank needs to be safe for a 0.1% probability event. Where communities are adjacent to the bank, the Middle Level Barrier Bank needs to be safe for a 0.01% probability event.

What are we doing?

We are raising the Middle Level Barrier Bank between Earith and Welmore Lake Sluice. Other associated works include:

  • building the foundation and walls for fitting a demountable barrier at Welney (we will be asking for your views on the timing of this work below);
  • building a new wall at Welches Dam Pumping Station;
  • extending a retaining wall at Sutton Gault;
  • decommissioning the Black Sluice culvert (near Earith).

We started construction work in 2017 and expect to finish in 2022. Because of the importance of the overwintering and breeding bird populations on the Washes, we can only work on the bank during a short period in the summer to autumn months. This is from mid-July to the end of October each year. We have allowed further two years for the areas of newly seeded grass to establish during 2023 and 2024. The grass plays an important role in the stability of the bank and it needs to be well established before we can allow public access back onto the bank. 

Grass growing on the banks

How is the work developing?

We started work in 2017 whilst still finalising the detailed design. We phased the works in different locations as the detailed design became available.                                            

Year 1 works (2017)  - We found material in the bank that was different to what the ground investigation results showed. When we analysed this material over the winter period (2017/18) we found that we could reuse most of this material but not all. The material that we could use needed further treatment before it was ready and this was time consuming. The material we could not reuse we stockpiled and removed from site.

Due to these ground conditions the design changed and we needed to import more material. This additional work, along with long periods of wet weather, delayed the first section of works and extended the 3-year programme to 4 years.

Year 2 works (2018) - As we progressed through the second year of construction, the weather was favourable and we completed all the work from the first year and the second year's work without any delays.

Year 3 works (2019) - This was a challenging year. The design evolved and the bank profile changed, increasing the footprint of the Middle Level Barrier Bank. Our contractor employed more resources and used larger machinery to import and place larger quantities of material at Welney and Mepal.  However, the exceptionally wet weather during September and October caused delays when the clay material we are placing on the bank became too slippery and dangerous to continue working.

Because of this, we couldn’t complete the work near Welney in 2019.  We will need to return in 2020 to complete the bank works. Subsequently we will complete the barrier works across the Wash Road in 2021 (year 5).

Year 4 works (2020) - We will continue the works near Welney that we couldn’t complete in year 3. The increased footprint on the bank has reduced the space the contractor has to work in. They will need to use smaller machinery to manoeuvre in the workspace safely, particularly near Welches Dam. This means we will be importing smaller loads of material which will increase the time to complete this section.

The amount of material we need to complete the project has increased from 320,000 tonnes to 487,000 tonnes. All these changes have increased the overall construction programme from 4 years to 6 years.

We are monitoring settlement on the bank works that we completed in years 1 and 2 to ensure that it is as expected. Once we have collected sufficient survey data we can determine whether we need to  top up years 1 and 2 as either part of these works or as part of future maintenance works.

bank worksBank works

Public footpaths

The grass is important on the reservoir bank. As the grass grows, the roots help to stabilise the bank and reduce erosion. We use a mixture of different seeds to get a variety of different grass species.

 Over the winter and spring months we regularly inspected the banks and grass growth on sections of work that we had completed. The grass is growing and the footpath diversions will stay in place until there is sufficient cover on the bank.

Next steps

We are planning to do the Welney Wash Road barrier wall construction in 2021.

We are asking for your views on timing options 

For further information contacts us via the Public Liaison Officer on 07534 457348

Events

  • Public drop-in event - Eartih

    From 25 Jun 2019 at 16:00 to 25 Jun 2019 at 20:00

    Join us to find out about the progress of the works and what we are planning for this year.
    Rectors Hall, Earith, PE38 9PX
    You can contact our Public Liaison Officer, Monica Stonham, for further information on 07534 457 348

  • Public drop-in event - Welney

    From 26 Jun 2019 at 14:00 to 26 Jun 2019 at 20:00

    Join us to find out about the progress of the works and what we are planning for this year.
    The William Marshall Centre, Hurn Rd, Welney, PE14 9SD
    You can contact our Public Liaison Officer, Monica Stonham for further information on 07534 457 348

  • Weekly surgeries

    From 23 Jul 2019 at 10:00 to 31 Oct 2019 at 17:00

    Find out more about the work we are doing during the following surgeries:

    EARITH ON WEDNESDAYS
    AT RECTORS HALL
    10am - 12pm

    MANEA ON THURSDAYS
    RSPB WELCHES DAM
    10am - 12pm

    WELNEY ON THURSDAYS
    LAMB & FLAG PUB
    3pm - 5pm

  • POSTPONED TO JUNE 2020

    From 18 Mar 2020 at 15:30 to 18 Mar 2020 at 19:30

    Join us at this event to provide your preferred option on the timings to do the Welney Barrier construction work. We will also showcase the work up to date and what's next for this summer's work. At the William Marshall Centre, Welney, Hurn Rd, Welney, PE14 9SD

Audiences

  • IDBs
  • Local authorities
  • District and parish councils
  • Environmental bodies
  • Land owners
  • Farming associations
  • Drainage associations
  • RFCCs
  • Elected representatives, including MPs

Interests

  • Flood management