Irwell Vale, Strongstry and Chatterton Flood Risk Management Scheme (not currently progressing)

Scheme Overview

Update Winter 2023 – The proposed Irwell Vale, Strongstry and Chatterton Flood Risk Management Scheme has been going through its appraisal in line with government guidance leading up to Outline Business Case (OBC) submission. Unfortunately, due to a significant gap of c.£9m in available funding, a decision has been made to halt the scheme. The Environment Agency and its partners understand this is extremely disappointing to all those involved in the scheme and in particular, the local residents of all three communities.

The Environment Agency appraised the flood protection options for the 3 communities. The appraisal consisted of the evaluation of a long list of options, community engagement, identification of the preferred option being ‘linear defences’, refinement of the preferred option including the identification of associated constraints and opportunities, and site surveys and investigations.

The Preferred option (linear defences) was determined by taking into consideration technical feasibility, cost, economic benefit, buildability and environmental impacts. The surveys included Heritage surveys, Environmental/Ecological surveys, topographical surveys and Ground Investigations. The output of these surveys and investigations were reviewed and informed further hydraulic modelling of the flood risk to the communities. The agreed final concept would have fed into an Outline Business Case which has to go through an assurance process internally.

Click the ‘Drawings of proposed alignments and defence heights’ section within the ‘Consultation’ sub-section of the ‘Historical Information’ section on the left to view the schemes proposed alignments and defence heights.

Historical Information

The works outlined in this section were carried out prior to the end of 2023.

Flooding Sources

The communities of Irwell Vale, Strongstry and Chatterton are hydraulically linked by the River Irwell and are at risk from fluvial (river) and pluvial (surface water) flooding. The Environment Agency, with support from its partners are assessing these risks. As the valley is steep sided, the flood events tend to be extremely flashy meaning the communities do not get much warning before a flood event. The communities have a long history of flooding with most recent events being in 2007, 2012, 2015 and 2020. These were linked to high river levels in the River Irwell.

The Environment Agency has worked closely with the community to try and understand the flooding mechanisms and a post-event review was developed by the Partnerships and Strategic Overview (P&SO) team in April 2017 following the events of Boxing Day 2015.

The surface water flooding is associated with the capacity of the existing drains and flooding from non-main rivers. There are multiple areas where surface water is a risk and a surface water pump was installed at southern end of Meadow Park in Irwell Vale in 2019/20 to assist with the dispersal of surface water from the rear of Meadow Park into the River Irwell. The risk of surface water is being included as part of the wider FRMS appraisal process.

There is also a groundwater flood risk impacting the Meadow Park area in Irwell Vale.

Funding and Partnership Funding

The scheme had been leading with a total scheme estimated cost of £14.7m. However, the Environment Agency were aware of increased costs associated with inflation on construction costs, increased temporary works costs and the need to construct new flood storage areas to mitigate for pass forward flow of the river Irwell downstream, due to the proposed construction of linear defences in Irwell Vale. These cost increases, in addition to new government legislation on Biodiversity Net Gain (BNG) resulted in the cost estimate increasing to £23m. The Environment Agency understand this is a significant increase and are really disappointed this has maintained the funding gap.

Part of the Outline Business Case (OBC) includes the “Partnership Funding Calculator”. The Environment Agency must use this to calculate what percentage of total scheme costs the Government is prepared to pay for. The Partnership Funding Calculator prioritises reducing the flood risk to residential properties because this is primarily what the Government make funding available to us for. They currently estimate that the Government contribution to this scheme is £5.1M which means private contributions will be required to fully fund the scheme. To date, contributions have been secured through the ‘Regional Flood and Coastal Committee Local Levy’, ‘Asset Replacement Fund’ and ‘Frequently Flooded Communities’. Further contributions would be required to fund the scheme.

Previous Public Consultation

This Environment Agency consultation is now closed. However, the consultation documents are available to download below but are for information only.

Community Drop in October 2023

Please click here to download the Environment Agency slide pack containing the community update.

Latest Newsletters

Irwell Vale, Strongstry & Chatterton Flooding Update Newsletter July 2022
Irwell Vale, Strongstry & Chatterton Flooding Update Newsletter August 2021

Images

Previous flooding at Irwell Bridge in Irwell Vale (Aitken Street)

Previous flooding at Lumb Bridge looking towards Meadow Park in Irwell Vale

The Flood Hub