Summer 2003

Flood Defences in the River Alt Area

The Environment Agency has started a review process, looking at the flood defences in the area surrounding the River Alt - referred to as the Alt catchment. It forms part of an overall plan to make sure that our current operations are reliable, efficient, up-to-date and in line with modern thinking.

The first strategic stage of the review is now complete. This factsheet summarises the main findings and provides a plan for the way forward.

The River Alt Catchment
The Alt catchment is around 15 miles long by 6 miles wide - 90 sq miles in total. The catchment can be readily split into two main areas: the Upper and Lower Alt.

The Upper Alt has mixed land-use, with rich agricultural land and urban areas, including Huyton, Knowsley, Kirkby, Aughton, Maghull and Aintree. Flood risk is generally very limited here due to the lie of the land and good planning to avoid any development too close to the river.

The Lower Alt covers the area from Maghull to the coastline between Crosby and Ainsdale, within which the main urban development is Formby, situated on a slight rise in the ground. Much of the remainder of the Lower Alt catchment is very low-lying land and so, in turn, the risk of flooding is higher. A number of flood defences have therefore been built over the years to help protect the area:

  • A 20 mile network of embankments protecting farmland.
  • A network of drainage ditches in the areas behind the embankments, much of the water from these ditches gets pumped into the River Alt and Downholland Brook.
  • A very large pumping station at Altmouth (the mouth of the Alt River), which acts as a barrier to prevent tidal flooding of the Lower Alt area.

    The Situation
    The likelihood of flooding is low if all the flood defences perform as intended. However, there are concerns over reliability of the existing defences to perform for years to come, especially as the Altmouth Pumping Station was built over thirty years ago. It is now time to review whether this station is still the best way to provide flood defences. We need to be sure that the flood defences provide value for money, are environmentally sound, and meet the needs of the catchment as a whole both now and in the future.

    The Way Forward
    A number of possible ways forward have been considered, but two feasible options have now been identified:

    to continue with the current defences, relying on a system of embankments and the Altmouth Pumping Station.


    to move to another method of flood management, which would involve returning some land to natural floodplain (known as 'managed realignment'). It is very likely that a tidal barrier at Altmouth would still need to be retained. This option would involve creating wetlands, ideal for wetland birds such as avocet, black tailed godwit, lapwing and little ringed plover.

    What happens next?
    When compared with the current defences, managed realignment has the potential to offer a number of benefits. However, there are advantages and disadvantages for both options, so we will be carrying out further work before making a final proposal.

    It is important to remember that we are only at the very initial stages of investigations and throughout the review process we will be speaking with all relevant local parties. We will listen to and take into account any views or concerns raised.

    The Environment Agency expects to make an interim recommendation on the proposed way forward in 2004 and a final recommendation by Summer 2005. In the meantime, we will keep you up to date about any important developments. Throughout all of the review process, you will have the opportunity to tell us your views or concerns.

    If you have any questions or comments please contact:

    Philip Hunter (01925 622048) or Kevin Keating (01925 622043), Atkins, Thomson House, Birchwood Park, WARRINGTON. WA3 6AT
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