Greater Manchester - Wigan Flood Alleviation Scheme

  • Phase 1: Walls

  • Phase 2: Dam

  • HydroBrake installed to help control flood flows.

  • Phase 2: Dam in operation

Overview

The Wigan Flood Alleviation Scheme was constructed by the Environment Agency between 2007 - 2011 to reduce the risk of flooding to 750 properties from the River Douglas and its tributaries in the town of Wigan.

The first phase of the works was completed in 2008 and involved the construction of new and raised flood defence walls and embankments on the River Douglas through central Wigan. The first phase of the scheme raised the standard of protection to 1 in 20 years, or 5% risk of flooding in any one year.

This phase involved the construction of 1 kilometre of reinforced concrete flood walls and 300 metres of earth embankments in the Poolstock area of Wigan. Alongside the walls a riverside footpath was contructed at a higher level to allow for views of the river to be maintained given the increased wall heights.

The second phase of the works was completed in 2011 and involved the construction of an earth dam across the River Douglas Valley forming an upstream storage reservoir. This further increased the standard of protection to 1 in 100 years, or 1% risk of flooding in any one year.

These phase 2 works involved the construction of a 150 metre long, 8 metre high earth embankment dam across the River Douglas in the Swinley Area of Wigan. The Coppull Lane Flood Storage Area formed by the dam can store up to 400,000m3 of flood water, which is equivalent to 160 Olympic swimming pools. This work involved changing the river alignment to allow for normal flows to pass through the new 100 metre long concrete culvert constructed beneath the dam. The Dam includes a footpath across the top which connects into the existing footpaths along the Douglas Valley connecting Wigan Town Centre to the Haigh Hall Estate.

Benefits


The Wigan Flood Alleviation Scheme combines traditional flood defence walls and embankments next to the River Douglas in Wigan Town Centre and upstream storage in the steep sided River Douglas Valley at the Coppull Lane Flood Storage Reservoir. The scheme provides a 1 in 100 year standard of protection to over 750 properties in the town of Wigan.

Since construction was completed in 2011 the scheme has successfully protected properties from flooding following heavy and prolonged rainfall in both June and September 2012. During both events the walls and embankments in the town contained flood waters and the Coppull Lane Flood Storage Reservoir held back over 6 metres depth of water. Flood events of this magnitude could potentially have lead to significant flooding of hundreds of properties, within the town of Wigan.

The scheme has also had a positive impact on the environment in Wigan. The scheme maintained a flood plain at Parson’s Meadow which is an important nature reserve area within Wigan including wetland habitat. The Phase 1 works also introduced improved footpaths and cycle routes in the town centre that now provide views of the river. The roads next to the Phase 1 works have since been altered as part of a highway improvement scheme in Wigan. The Phase 2 works involved the creation of a habitat enhancement area immediately downstream of the Coppull Lane Flood Storage Reservoir which included the creation of ponds and the planting of thousands of trees and shrubs. The Phase 2 works also included the improvement of footpath connectivity been Wigan Town Centre and the Haigh Hall Estate.

Further Information


The flood storage reservoir uses the innovative technology of HydroBrakes to control flood flows. The HydroBrake technology is a passive control solution that requires no operation or manual input for it to be effective. The HydroBrake is essentially a cone on its side with an inlet in the side, and outlet at the bottom end. The shape of the HydroBrake is the reason it controls flood flows as it contains no moving parts. The principle is essentially the same as removing the plug from a bath and the vortex formed controlling the amount of water passed through the HydroBrake.

The Coppull Lane Flood Storage Reservoir contains 2 of these HydroBrakes, which have a combined capacity larger than any other HydroBrake installation in Europe to date.

Contacts


John Greenway, Environment Agency

enquiries@environment-agency.gov.uk

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