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Flood Alleviation Scheme

Update – April 2014

Leeds Flood Alleviation Scheme Fly Through, via YouTube, is now available to view on this web page. The Crown Point Weir animation can now be accessed by using the external link under the external links heading.

Woodlesford
The Woodlesford Enabling Works have been awarded to BAM Nuttall Limited. The works are programmed to start on-site the week commencing the 10 February 2014 for a duration of 22 weeks.

Knostrop Quay (KQ) Arm /Old Mill Lane Basin Adjacent to the H2010 Development

We are aware of some concerns by local residents living near to this section of Knostrop Cut. Alterations to the area are being investigated to take into account comments and feedback received from stakeholder groups.

To facilitate the conveyance of water out of the city centre during a flood event we need to remove a length of Knostrop Cut which contains the Trans Pennine Trail (TPT) cycle route.  The removal of the cut, and re-grading of the canal along this length, is an essential component of the scheme which compliments the movable weirs, enabling us to lower the height, and in some instances eliminate the need for physical flood defences throughout the city centre.  

In light of this we are proposing to divert the TPT onto the left bank of the River Aire, crossing an additional bridge in the vicinity of KQ Arm/Old Mill Lane Basin and then back again over a new bridge to be located near to the Knostrop Weir.  

Stakeholder engagement had raised concerns that the diversion was diminishing the quality of the TPT in this area and a request was received asking that we consider improvements to the route.

Taking into account the feedback, work is being undertaken to consider further options to reduce the impact on the TPT route 

‘LFAS - Draft TPT Diversion At Knostrop Cut’ showing the opportunities and constraints of the TPT diversion option is available to download from the documents section of this page.

One option being considered involves diverting the TPT across the KQ Arm/Old Mill Lane Basin and the lock to by-pass a length of TPT which currently loops around the wharf passing an industrial building and a substandard bridge crossing. The footway in this area is narrow, poorly maintained and generally not complementary to the high quality TPT aspirations. Additionally KQ Arm/Old Mill Lane Basin traps litter and is difficult to maintain due to siltation. 

If this option was to be implemented it would be achieved by either providing a wetland area or a high quality landscaped garden space behind the footway diversion.


Further discussion with stakeholders is necessary to fully evaluate the TPT route options in this area before we will be in a position to consult members of the public on any proposals. We would like to reassure residents of the H2010 development that there will be further consultation on the draft details before the plans are finalised.
 

General Scheme
 

Planning permission for the flood defences in the City Centre and Holbeck, including the removal of Knostrop Cut, has recently been granted.  Detailed design work for these parts continues to be progressed and the design and build contract is programmed to be tendered in April 2014.
  
Throughout June and July 2013 Leeds City Council consulted businesses and members of the public regarding proposals for the Leeds Flood Alleviation Scheme. Approximately 3000 leaflets were distributed via a letter drop to residents in the area either contained within or located in close proximity to the proposed scheme and through our stall at the Leeds Water Front Festival on the 29th and 30th of June 2013.The aim of this consultation process is to inform and engage stakeholders to give opportunity to influence the scheme and their surroundings.

 

The leaflet contained a questionnaire and sought the views and opinions of businesses and members of the public. The questionnaire was also made available online via a link from this webpage to our ‘Talking Point’ community engagement service. The consultation questionnaire period has now come to a close. A summary of the feedback received is now available to view (LFAS Feedback September 2013.pdf) in the documents section of this page.

Background

Flood risk is increasing throughout the UK and Leeds is no exception. In recent years Leeds city centre has come very close to flooding several times.
At the moment there are no formal flood defences along the River Aire. The River Aire has a steep profile with over 25 tributaries upstream of the city and a fairly narrow flood plain.  With high annual average rainfall and a rapid response to rain, this means that the City of Leeds is vulnerable to flooding.
There is also a significant risk of surface flooding from drains and sewers that cannot discharge when the river is high.
To protect businesses, homes, buildings, the transportation network and the city economy in the future, we need to put flood defences in place.

History

Flood records start in the mid 18th century and the worst recorded flood was in 1866 when a metre high wall of water ran down Kirkstall Road into the city.  In 1946 there was flooding recorded all along the River Aire.  The largest recent event  was in autumn 2000 when water levels came within 10cm of flooding the city centre to the extent suffered in 1866.  Since then, there have been smaller floods in 2002, 2004, 2005, 2007, 2008 causing disruption to those living, working and commuting into, out of and through the city including closure of the railway station.
It has been estimated that over 4,500 properties are at risk of flooding and approximately £450m of direct damage would be caused by a major flood from the River Aire in Leeds.

Previous Scheme Proposals

The Environment Agency previously considered a comprehensive scheme for the River Aire from Newlay Bridge in Kirkstall to Woodlesford using flood defence walls.  This would have provided protection against a flood event that was likely to occur once every 200 years (such an event has a 0.5% chance of occurring in any given year). This scheme was estimated to cost over £190m and was deemed unaffordable.
Previous consultation to the proposed 200 year flood defence scheme had indicated that the flood defence walls were poorly received in some areas. This was due to the wall height required to achieve the 200 year flood event level of protection, some of which were 2metres high along the side of the river in the city centre.

New Scheme Proposals and Project Details

Now Leeds City Council, working alongside the Environment Agency, British Waterways and other partners, are planning proposals for protection against flood event likely to happen once every 75 years in Leeds City Centre between Leeds railway station and Knostrop Weir (such an event has a 1.3 % chance of occurring in any given year).

A plan, showing the area at risk from a 1 in 75 flood event is available to download - "Leeds City Centre 1 in 75 Flood Event Risk Boundary".

The new 1 in 75 flood event protection scheme would:

  • Remove the existing weirs at Crown Point in the city centre and at Knostrop Cut and install moveable weirs that can be lowered when the river is high, causing the water level to drop. An animation showing the typical operation scenario of the Crown Point weir can be seen in the video clip above.
  • Construct landscape defences such as low embankments, terracing and riverside walls; at low points along the riverbank.
  • Remove Knostrop Cut to merge the Canal and River Aire which will create additional flood water storage and help to lower water levels in flood conditions.
  • Provide flood defences along a length of Hol Beck located on Water Lane.
  • Provide defences to Woodlesford in the form of low level embankments to achieve a protection against a flood event that is likely to occur every 200 years.

Planning permission for the movable weirs has been granted. Details for this can be viewed by clicking here.

A leaflet showing a general overview of the full scheme - "Leeds Flood Alleviation Scheme Leaflet" is available to download.

Larger visualisations of the images above may be viewed by downloading the link on this page.

The new scheme is being designed to be environmentally friendly, and by providing the moveable weirs and removing the cut it means that the walls will be considerably lower in height and the numbers will be significantly less than those originally proposed by the Environment Agency in the 1 in 200 year scheme.  Many of the walls will be in the form of terracing/seating etc. to blend in with the local environment.

The removal of Knostrop Cut 'island' will necessitate the removal of trees which are growing on the manmade 'island' in the river which forms part of the Transpennine Trail (TPT) footpath and cycling route. The TPT will need to be relocated to the north bank of the river when the 'island' is removed.

An Environmental masterplan for the north bank of the river at Knostrop including ecologically appropriate design for habitat creation and associated tree planting will be implemented when the defences are constructed. The overarching aim will be to enhance the River Aire Green Corridor and to provide opportunities for biodiversity and for leisure including cycling and walking, improving links for people and wildlife between the city centre and the wider Lower Aire Valley.

Funding and Programme

The scheme is estimated to cost in the region of £50.5m and is being funded through a partnership supported by Defra and the Treasury, Leeds City Council and local businesses.

The works are due to commence on site in 2013/2014 and are projected to be completed in 2016.

Frequently Asked Questions can be downloaded.

The following documents are also available to download in the documents section of this page:

  • A leaflet showing the general overview of the full scheme - Leeds Alleviation Scheme Leaflet
  • Location Plan - Full Scheme Overview (CC-001)
  • Scheme Overview - City Centre (CC-002)
  • Scheme Overview - Knostrop Cut (CC-003/CC-004)
  • Scheme Overview - Woodlesford Defence Proposals (CC-010)
  • Scheme Overview - Holbeck Flood Defence Proposals (CC-011)
  • City Centre Flood Defence Proposals (CC-005 to CC-009)
  • Landscape Drawings (Location Plan/Landscape Drawings) (CC-200, CC-201-CC218)
  • LCC 1 in 75 Flood Event Risk Boundary - added 13 February 2014
  • Contract Drawings CC0001-CC0007 - Added 12 March 2014
  • Contract Drawings CC0008-CC0012 - Added 12 March 2014
  • Contract Drawings CC0013-CC0018 - Added 12 March 2014

 


Frequently asked questions

What level of protection is provided by the scheme?

​The aim is to provide a 1:75 standard of protection against flooding.

What do we mean by flood risk?

​The chance of a flood happening can be expressed as).

Generally, the higher the figure used in the description of the flood risk, the less chance of it happening.  So for example:

An area with the chance of flooding of a 1 in 75 (1.3 percent) in any one year has less chance of flooding than anothe either; a ‘chance’ (i.e. a 1 in 75 chance of flooding in any one year) or a ‘probability’ (i.e. a 1.3 percent annual probability of floodingr village with a 1 in 25 chance (4 percent) in any one year.

It is important to understand that a 1 in 75 chance of flooding in any one year does not mean that level of flood will happen once every 75 years.  Nor does it mean that if the flood hasn’t happened for the last 74 years, it will happen this year.  ‘Any one year’ means exactly what it says, in that the risk is expressed on a yearly basis.  A flood may also occur more than once in a year.

Why has this level of protection been chosen?

​The current agreement Government has with the Association of British Insurers (ABI) is that ABI members make flood insurance for domestic and small businesses available as a feature  of standard household and small business policies if the flood risk is no significant ( this is generally defined as no worse as 1 in 75 annual probability of flooding). 

How does the introduction of movable weirs improve flood protection?

​The river level is held artificially high by the existing weirs which were built to allow navigation. The proposed movable weirs will, in a flood event allow the river levels to drop by up to 1.0m

Will flooding risk be increased further downstream?

The scheme will have an immeasurable effect on the risk of flooding downstream of Thwaites Mill. There are large areas of designated floodplain from the Mill downstream.

Will boaters be affected by the proposals?

No, the weirs will only be lowered during actual events and when the speed and depth of water in the navigation is too great for boats to navigate.

How long will it take to build the defences?

The aim is to have the first phase of works completed by June 2015.

What about flood protection upstream of Leeds Station?

The scheme will protect the city centre section and not sections upstream of the train station. Future phases will include addressing flooding upstream of the station, however, these will be subject to the availability of future funding.