Avonmouth Severnside Enterprise Area (ASEA)Ecology Mitigation and Flood Defence Project

Introduction…The Avonmouth Severnside Enterprise Area is one of six strategically important employment areas in the West of England. 12,000 new jobs will potentially be created here by 2026. In order to help this development continue there is a need to:

• Manage flood risk to keep pace with climate change and sea level rise.• Ensure sufficient wetland habitat is created to protect the internationally important habitats

and species of the Severn Estuary site.

These measures should also have benefits for the local community.

South Gloucestershire Council, Bristol City Council and the Environment Agency are working together to identify where works are required and to secure funding to ensure they can be delivered. The project is at an early stage and these boards provide an overview.

Study area…The study area extends from Avonmouth Docks in the South to Austin the North. We will be focussing on five key areas.

In areas 1, 2 and 3 we will be looking at what flood defence works may be required.

In areas 4 and 5 we will be looking at ways to provide habitats for birds.

Map 1 – Study area

© Crown Copyright and database rights 2016 Ordnance Survey 100024198

Avonmouth Severnside Enterprise Area (ASEA)Ecology Mitigation and Flood Defence Project

Flood defences…We are looking at how best to ensure the Enterprise Area and existing residential properties benefit from a consistent standard of flood protection. We are using flood models to identify low spots in existing defences and to look at options required to address these in the future.

Any works to the flood defences would depend on securing the required funding and are likely to be delivered in phases, as part of a long term project. The areas of greatest need are likely to be tackled first.

Area 1 – SevernsideThe defences at Severn Beach are in good condition. We are looking at whether we will need to increase the height of the defences to keep pace with sea level rise and climate change.

Area 2 – Avonmouth DocksWe are working closely with the Port to look at flood defences on their land and how these could be managed into the future. This would benefit Avonmouthvillage.

Area 3 – Chittening WarthWe are looking at options to continue to manage the flood risk in this area. There are important ditches and streams (known as rhines) which flow into the Severn Estuary that need to be considered.

Avonmouth Severnside Enterprise Area (ASEA)Ecology Mitigation and Flood Defence Project

Flood defence types…Where we think works to the existing flood defences may be required, there are a number of different methods we could use. Each method has its own advantages and disadvantages. It may be that different methods will need to be used in different locations.

We could work on the existing defences by:

• Building up the existing flood banks (or embankments). Any additional land take would need to be on the landward side to avoid building on intertidal habitats.

• Adding structures to the top of the existing sea wall, where the existing defence is in good condition.

• Using metal walls (called sheet piles) to give extra height. These are particularly suitable where there is a limited amount of land as they are narrow and do not take up much space.

Adding structures to the top of an existing defence may be an option in some locations.

Sheet piles are narrow, impermeable and can go deep into the ground to cut off water flow. This is an option that may be suitable in some locations. Measures can be taken to help improve their appearance.

One option is to increase the height of the existing flood banks. The new slopes could either be vegetated or made from hard landscaping materials.

In some areas the habitat in front of the defence is legally protected and this will affect what kind of defence is used and how it is built.

Avonmouth Severnside Enterprise Area (ASEA)Ecology Mitigation and Flood Defence Project

Ecology…

A key part of the project is to provide new habitat for birds. This needs to include:

• Wet grassland to encourage wading birds such as lapwing, common snipe and curlew.

• Open water to encourage wildfowl such as gadwall, teal, mallard, shoveler, pochard and tufted duck.

These are all species which are protected by the various designations that cover the Severn Estuary.

Providing these habitats will ensure the Enterprise Area fulfils its economic potential without impacting upon the internationally recognised wildlife of the Severn Estuary.

We are looking at Area 4, Hallen Marsh and Area 5, Northwick because they:

• Already function as wildlife corridors.• Are low-lying with wet ground.• Are relatively open.• Are close to the Enterprise Area and Severn Estuary.

Some of the wading birds we aim to encourage. Top – common snipe. Bottom - lapwing

Some of the wildfowl birds we aim to encourage. Top – shoveler. Bottom - gadwall

Acknowledgements:Shoveler - Hugh Venables licensed under the Creative Commons Attribution-Share Alike 2.0 Generic license, via Wikimedia Commons. Gadwall – Andrew Dunn licensed under the Creative Commons Attribution-Share Alike 2.0 Generic license, via Wikimedia Commons.Common snipe - Marek Szczepanek licensed under the under the Creative Commons Attribution-Share Alike 3.0 Unported license, via Wikimedia Commons.Lapwing - Charlesjsharp licensed under the under the Creative Commons Attribution-Share Alike 3.0 Unported license, via Wikimedia Commons.

Avonmouth Severnside Enterprise Area (ASEA)Ecology Mitigation and Flood Defence Project

Wetland habitat types…

Open water and wet grassland can be formed by:

• Diverting water from the existing ditches (known as rhines) onto the fields.

• Pumping water from the ditches to wet the fields.• Widening the existing ditches to create larger areas of

standing water.• Digging down to access groundwater to create new ponds

or scrapes.• Building low banks to trap rainwater.

The wetland habitats and any works to the ditches would be designed so that they do not increase flood risk to houses, businesses or other infrastructure.

We are working with landowners, Natural England, ecologists at the Councils and the Lower Severn Internal Drainage Board (who manage the network of rhines) to identify the most effective measures.

An important consideration is to ensure the wet grassland can continue to be farmed in a way that is compatible with the new habitat.

These photos show the type of wet grassland required to support the important birds of the Severn Estuary.

This shows the type of open water habitat required to support the important birds of the Severn Estuary.

Avonmouth Severnside Enterprise Area (ASEA)Ecology Mitigation and Flood Defence Project

Programme…This project has a long and detailed programme.

Opportunity for comment…

• Spring 2017 – Public events will provide everyone with an opportunity to discuss our more developed proposals.

• Email – Please feel free to email us at any time ASEA@environment-agency.gov.uk

• During the planning process – Where planning permission is required there will be a further opportunity for everyone to comment.

Please keep an eye on our website for further details

www.insouthglos.co.uk (Enterprise Areas – Avonmouth Severnside – Flood and Ecology)

Indicative timescale2016 2017 2018 2019 +

Surveys

Select schemes

Public consultation

Apply for planning

Apply for funding

Construction