How our teams manage flood risk and water levels on the Gwent Levels

Overview

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The Gwent Levels are a historic landscape of international significance that are characterised by a complex network of fertile fields and historic water courses (known locally as reens) that stretch across 180Km.

Running alongside the Severn Estuary,  this historic landscape is made up of several unique habitats that contribute to the special wildlife interest here and requires careful management.

Our management role

Our teams play a key role in managing flood risk and water levels across the Gwent Levels.

Our Internal Drainage District team help to maintain approximately 105km of the water courses and drainage channels; whilst our Integrated Workforce and Engineering teams maintain approximately 40km of raised sea defences and associated structures between Chepstow and Cardiff.

They also maintain approx. 64km of main rivers and the flood storage reservoir at Peterstone.

Using permissive powers, the teams can carry out maintenance, improvement or construction work on the watercourses, to help manage flood risk to people and properties and protect the environment.

To ensure they are carrying out the work as effectively as possible, the teams have an annual maintenance programme, to carry out vital work which includes:  

• Grass cutting
• Sea outfall inspection
• Weed control
• Minor construction work

All of these activities are carefully managed and we consult our in-house biodiversity specialists to determine the best time for maintenance work to be carried out and to obtain the necessary legal permissions to undertake such works.

We plan our works to take account of this advice, whilst ensuring we meet any legal requirements. This helps ensure we balance maintenance requirements with the needs of the Gwent Level’s habitats and species.

Grass cutting

Throughout the ‘growing season’ in March to October our internal teams and contractors cut the grass at these sites to help keep the flood defences we maintain in good working order to protect local communities from the risk of flooding.

These banks help provide a vital defence against flood risk, and regular maintenance helps us to ensure that  embankments are resilient when they are needed.

It also allows us to monitor for any signs of damage from livestock; illegal activities, such as off road vehicles; or burrowing animals.

Before any mowing begins, a site supervisor will walk the site, carefully looking for nesting birds and other wildlife.

Peterstone Reservoir requires more regular cutting due to the Reservoirs Act so engineers can check the integrity of the banks. The necessary ecological checks are undertaken prior to each cut.

At a small number of locations we are trialling ‘cut and collect’ methods, where we remove grass arisings away from the sea wall to reduce nutrient input and encourage a greater diversity of herbs and grasses. Cuts are undertaken as early and late in the growing season as possible to retain a nectar resource for pollinators, including the rare the shrill carder bee – for which the Gwent Levels is a stronghold.

Sea outfall inspection

There are over 20 sea outfalls on the Gwent Levels, which are inspected and maintained to help keep them in good working condition.

They are regularly inspected for blockages and debris  to help prevent the risk of flooding.

Weed control

As part of our management and maintenance work, we also have an annual programme of herbicide spraying and de-weeding.

This helps to tackle any Invasive Non Native Species (INNS) identified on the reens and embankments - such as Himalayan Balsam,  Japanese Knotweed and Giant Hogweed.

Affected areas are sprayed directly using an approved formulation of herbicide, suitable for treatment adjacent to the watercourse.

All spraying is carried out by qualified operators in suitable weather conditions. 

De-weeding is undertaken annually using heavy plant machinery to remove a build-up of weed from within the watercourses. This is to allow for effective conveyance of water and minimise flood risk.

Minor construction work

Occasionally you will see our staff undertaking small scale construction activities such as fencing or repairs to our structures and assets. These works will be assessed and planned to minimise any disturbance to the local environment and will use sustainable products where necessary.

Useful links

Living Levels: Recapturing, enhancing and celebrating The Gwent Levels