Overview

Lowdham Cocker Beck Flood Alleviation Scheme

Key Facts about the Lowdham Flood Alleviation Scheme

• 195 properties better protected from flooding
• 1% Annual Exceedance Probability Standard of Protection
• 20% Biodiversity Net Gain target
• Enabling works start – 30 January 2023
• Main construction start – Spring 2023
• Fully operational – Autumn 2024

What is a Flood Alleviation Scheme?

A Flood Alleviation Scheme (FAS) is a scheme of work to manage flood risk, reducing the likelihood and impact of flood events to property and infrastructure. Risk management authorities in England, such as the Environment Agency, are committed to reduce risk from flooding and work in partnership to deliver the programme of flood and coastal erosion risk management (FCERM) schemes.

Why does Lowdham need a FAS?

In recent years the village of Lowdham has seen repeated property flooding occurring in 1999, 2007, 2012, 2013, 2019 and in 2020. The Cocker Beck is the source of fluvial flooding in the village, and is surrounded by properties and infrastructure, offering limited space for defences and flood storage. A FAS was constructed in 2000, using the recreation ground in Lowdham for flood storage. Unfortunately, it has proved insufficient in protecting properties from recent, large-scale flooding.

Recreation ground storage during the February 2020 flooding. (Source unknown)

What measures are included in the proposed FAS?

The Lowdham FAS explored the options to alleviate flooding within Lowdham and identified that upstream storage would be the most effective. A single site has been selected near Lowdham Grange, which is optimal for storing up to 87% of flood flows from the Cocker Beck and its tributaries.

Proposed Flood Storage Reservoir location.  (EA, 2022)

A reservoir to store flood flows is proposed for the site, which will remain dry most of the time, only filling with water when the Cocker Beck rises in certain flood conditions. The design will account for the effects of climate change throughout the lifetime of the proposed reservoir.

Due to the scale and position of the proposed flood storage reservoir, it will be classified as a Category A Reservoir under the Reservoirs Act, 1975. The Environment Agency will be the operator of the reservoir once constructed, to ensure it meets all statutory requirements and remains safe into the future. 

Clay to construct the earth embankments for the reservoir will mostly be excavated from the site itself. This offers a significant reduction in both cost and carbon emissions during construction, as well as reducin the need for vehicular movements, which could potentially have been disruptive for the community. Excess soil excavated to create the storage area will be used during the final landscaping of the site.

Proposed flood storage reservoir layout. (Arup, 2022)

Very careful consideration of the whole life carbon impact is being taken through the design process, and planning for both the construction and operational phase of the reservoir’s lifetime. We are trialling low-carbon concrete, which we plan to use throughout the reservoir structures apparatus if suitable.

Lowdham FAS Biodiversity Net Gain

The Scheme is aiming to achieve a 20% Biodiversity Net Gain (BNG), introducing new habitat enhancements for ecology local to the site. From December 2023, a minimum requirement of 10% BNG will have to be achieved by all developments, as part of the enactment of the Environment Act 2021.

A combination of on-site and off-site measures will be used to mitigate the development of the site and reach the 20% BNG target. We will be expanding existing woodland, creating new woodland on site, and enhancing existing habitat such as hedgerows and grassland.

In recent years, the spread of Himalayan Balsam, which is an invasive species that can dominate the banks of watercourses, has accelerated throughout the Cocker Beck catchment and can be found at the proposed reservoir site. We will be treating Himalayan Balsam in the Cocker Beck catchment, working in partnership with Nottinghamshire County Council.

Himalayan Balsam presence in the Cocker Beck circa early 2022. (NCC, 2022)

Lowdham FAS Progress

4th November - Submission of Full Business Case (FBC) to Large Project Approval Group (LPRG). The FBC is the final review of the scheme where the recommendation is made by LPRG for the investment decision to continue to site. The review process requires all major permissions and consents (planning permission) to be secured and all funding confirmed. The Team have been in close consultation with LPRG to secure special permission to continue through assurance while finalising the funding and the permissions and consents. The submission of the FBC is the significant milestone in the progress of the scheme and the furthers a scheme for Lowdham has gone before.

8th November - Full Planning Submission to Newark and Sherwood District Council (NSDC). Following the geometry changes to the reservoir basin design through this summer the Team have reissued the planning application to the local planning authority. The application has now been validated and can be found using planning reference 22/02188/FULM on the NSDC planning portal website (https://www.newark-sherwooddc.gov.uk/your-council/planning-services/)

Scheme progress through the Treasury Green Book Gateway Review process. (EA, 2022)

The Scheme is currently in the Full Business Case stage, and we are working through the detailed design. The Scheme is in the process of securing the licences, consents and permissions ahead of construction, and we are continuing environmental monitoring for protected species at the site. The table below sets out the key milestones for the Scheme.

 

1. Access and site establishment works
2. Earthworks and structures

The initial start on site will see our construction partner Jackson Civil Engineering establish the site compounds and setup the utilities such as electricity and a water supply. The first phase of the vegetation clearance will be completed ahead of the 2023 bird nesting season, clearing the north-eastern portion of the site to allow construction of the Control Structure.

All works are to be completed under supervision of an Environmental Clerk of Works (ECOW) who will continue the environmental active monitoring throughout the construction period.

Lowdham FAS phasing for vegetation clearance. Phase 1 is the northeast of the orange line (Arup & EA, 2023)

The second phase will commence after the 2023 bird nesting season concludes in September and will be followed with the start of the embankment earthworks and river channel re-alignment.

 

The Lowdham Cocker Beck Flood Alleviation Scheme is being delivered in Partnership with:

       

 

Flood Wall Repair

We have recently completed capital maintenance of a flood alleviation wall in Lowdham, along a 215m stretch of the Cocker Beck. The work reinstated the existing flood wall, where the watercourse flows adjacent to the playing fields in Lowdham, between Main Street and Epperstone By-pass. 

 

 

 

Our work on the Flood Wall has reduced the likelihood of flooding by diverting flood water to the storage area (playing field). We have reinstated the Flood Wall to its designed flood protection level and lowered the level of the storage area to provide additional capacity. This work will complement the proposed capital scheme to create additional upstream storage. 

Drone image of the Lowdham Flood Wall works. Environment Agency 2022

Lowdham Flood Wall works. Environment Agency 2022.

You can find details of our current maintenance programme in the area by searching for Lowdham on our Asset Management website or downloading the Cocker Beck maintenance schedule. 

 

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