Coggeshall, Feering and Kelvedon Flood Alleviation Scheme – information page

Overview

Following our public drop-in events with the Coggeshall, Feering and Kelvedon communities in summer 2019, we have continued work to finalise the design for the Coggeshall, Feering and Kelvedon flood alleviation scheme, which aims to protect these communities from further flooding.

As part of the design process, we have undertaken modelling of the River Blackwater upstream of Coggeshall. The outputs from this have helped to inform and refine the design of the scheme, including the dam, ensuring it will significantly reduce flood risk to the villages of Coggeshall, Feering and Kelvedon and benefit the surrounding communities. 

This scheme is designed to reduce the risk from river (known as fluvial) flooding from the River Blackwater, which floods because of intense or prolonged periods of rain falling across a large upstream catchment area, causing water levels in the river channel to rise and overflow into the floodplain.

Note: Surface water (also known as pluvial) flooding is caused by periods of heavy rainfall, causing water to flow over the land before reaching a river or draining into the ground. This risk will need to be managed separately. River flooding and surface water flooding do not always happen at the same time. View the Environment Agency’s updated risk of flood from surface water maps.

Once the design stage is complete, a planning application and supporting Environmental Impact Assessment (EIA) will be submitted to Essex County Council for their consideration and approval following their formal process,

Once the planning application is submitted to Essex County Council, everyone will have the opportunity to comment on the scheme. Background details about the scheme, including the original presentation boards explaining some of the changes made to the scheme’s design, are included on this web page.

There is also a video presentation to support the documentation that explains the scheme and planned phased construction. This is hosted on YouTube: https://www.youtube.com/watch?v=pfULOeddT-c

Coggeshall flooding in 2001

Background

In October 2001 Coggeshall, Feering and Kelvedon suffered from significant flooding. Since then, in May 2012 and February 2014 the villages experienced further flooding. Due to changing weather patterns, associated with climate change, the villages are expected to experience more frequent, more damaging flooding in the future.

In 2006 we commissioned a study to explore whether a scheme would be viable for the villages. The study demonstrated that the cost-benefit ratio for this area was low, resulting in options being too expensive to fund through our Flood Defence Grant in Aid (FDGiA) money. The study also highlighted the need to complete a hydrological model of Robins Brook, a “Main River” under our jurisdiction, before considering a future scheme. This work was completed in 2013 allowing us to carry out further investigation.

Out of the 8 options we consulted on in 2015, the scheme that received the greatest public support was that of providing flood storage within the River Blackwater. However, this option could not go forward for several reasons. Firstly, initial costs were estimated to be unaffordable, with no corresponding funding source available. Secondly, it failed to achieve the required levels of flood protection, as there is insufficient storage capacity within the Blackwater Valley.

In 2015 we approached Blackwater Aggregates to ask for their support in developing a low impact and sustainable flood alleviation scheme within the Blackwater Valley, which could provide the necessary 1% annual probability (1 in 100) flood storage across land under their control. Through our discussions it became apparent that by working together a long-term solution could be found.

The proposed flood alleviation scheme

Artist impression of the finished scheme

The flood alleviation scheme will reduce the impacts of flooding from the River Blackwater to the villages of Coggeshall, Feering and Kelvedon, through the creation of a dam and extended flood storage area. It will include:

1. Dam: A clay embankment (or dam) will cross the valley next to the football ground. The height of the dam will be approximately 5m at its highest point, as it crosses the river, and will reduce in height to taper into natural ground levels on either side.
2. Increased upstream storage area: Following the construction of the dam, we will be able to store more flood water upstream of its location within the valley, using the existing flood plain.
3. Extended flood storage area: An extended flood storage area will be created next to the river (to increase the storage capacity of the floodplain). This will be created by removing the underlying aggregates from the footprint of the site and large quantities of London Clay from the base. Once landscaped and restored, the new flood storage area will form an extension to the natural flood plain that will mean more flood water can be stored during a flood.
4. Connection point: The connection point between the existing floodplain and the flood storage area will run along the edge of the existing willow plantation. The ground levels across the flood storage area will match levels within the existing flood plain, which will allow flood water to naturally rise and fall as a flood occurs and subsides.

The scheme has been designed to hold more than 3 million m³ of flood water during an event. This will greatly reduce the volume of flood water reaching the villages of Coggeshall, Kelvedon and Feering, during a 1% annual probability (1 in 100) flood from the River Blackwater. When the river is flowing normally, the flood storage area will be dry and maintained as a floodplain meadow.

What has changed since the 2019 public drop-in events?

• The extended floodplain has been designed to provide bio-diverse habitats, connected to the existing floodplain  
• The shape and profile of the restored side slope, across the southern side of the Blackwater valley, has been shaped to provide differing side slope angles, sympathetic to the site’s setting and future land uses
• A crossing point will be established over Cuthedge Lane, midway between Deeks Cottage and Haywards   
• Permissive footpaths have been incorporated into the design of the scheme which will provide new links around the site, based on agreements with landowners and discussions with the Public Rights of Way Officer
• Additional areas of broad leaf woodland will be created across the site which will connect existing habitats with the flood alleviation scheme
• The dam itself has been made wider at its base following further analysis of the structure and local ground conditions. This has resulted in changes to the dam and realigned section of the river

We have considered the feedback from the public consultation events we held in 2019, and where possible made changes. Key to any changes is agreement from the local landowners. If the scheme is successful, we hope to build on the project and promote further opportunities for ourselves to work with local stakeholder groups, to explore other local initiatives which may be incorporated into the scheme, through partnership working.

Project funding

This project has received £1 million from central government ‘Grant in Aid’, plus £0.5 million in Local Levy (via the Environment Agency), and up to £8 million in direct funding contributions through the Blackwater Aggregates partnership. Blackwater Aggregates normal quarrying operations across the site will ultimately support in the delivery of a flood alleviation scheme, which would cost in excess of £25 million for the Environment Agency to deliver without the partnership approach.

If planning is approved for the scheme, the Environment Agency has already secured a further £2 million for future costs and ongoing maintenance of the scheme.