Sefton - Lunt Meadows Washland

  • Bursting of the River Alt banks, July 2010.

  • Extent of River Alt flooding, July 2010.

  • Raised embankments of the River Alt.

  • Flooded farmland in Lunt, July 2010.

Overview

Lunt Meadows Washland is a 75 hectare area of the River Alt floodplain owned by the Environment Agency. It is sited adjacent to an area of raised bank suspected to be the first point of overtopping in a flood event. In July 2010 the River Alt bank did breach in this location and an area of 80ha was inundated to a maximum depth of 1m.

The River Alt catchment is an “upside down” catchment, with its headwaters in the urban sprawl of Liverpool, flowing out across rural North Merseyside to the Altmouth pumping station, where it joins the Irish Sea. Through rural areas the Alt is raised above the surrounding land and entrained by earth embankments, part of a major land drainage/flood protection scheme carried out in the 1960s. This includes 6 smaller “satellite” pumping stations lifting water up from the surrounding land into the Alt.

This land is primarily high grade and intensively farmed. The urban upper catchment means heavy rainfall events are rapidly transferred into the river via the drainage network. The water quality in the Alt is poor and is currently failing by European standards.

In 2006 full planning permission was granted for a flood storage scheme at the site as a showcase of how flood risk can be managed with washland schemes, alongside the reconnection of the flood plain and re-wetting of dwindling peat supplies. Washlands are designed to operate as river levels rise, allowing water to spill from the river into controlled areas and reduce the risk of flooding to nearby properties. At Lunt Meadows the Environment Agency have constructed a low level inlet from the river, diverting a constant flow of water through the reedbed system before flowing back into the River Alt through an outfall. Essentially the site acts as a giant Sustainable Urban Drainage Scheme (SUDS), using natural land management techniques managed by Merseyside and Lancashire Wildlife Trust.

Benefits


As the spillway operates and water starts to fill the storage area, the flood peak level is reduced. Locally this should reduce water levels and allow surface water drainage networks to operate more effectively, reducing the impact of this flooding source on property. Local areas such as the Dovers and Whinney Brooks have previously been affected by flooding.

With increased urban development in the catchment, including a washland in the flood risk management system for this area will lower peak water levels and reduce the pressure on the existing embankments during any given flood.

The scheme has been developed to emphasise the habitat creation opportunities and create a wetland/washland rather than a pure flood storage area. The project is listed in the North West River Basin Management Plan because of the wider environmental improvements that it offers. The scheme consists of a mosaic of reedbed, open water (including ponds), wet grassland, hay meadow and floodplain grazing marsh. These are all important Biodiversity Action Plan habitats and will be a significant biodiversity resource both locally and regionally.

Previous water vole surveys have found some of the highest densities in the country and the proposed habitat creation will further enhance the population. It will also provide nesting opportunities for several key bird species, create new spawning habitat for fish coming in from the River Alt and attract invertebrates, for which there is a scarcity of habitat within the area. The site offers a tranquil natural resource for the local communities and to the neighbouring urban fringe.

In addition, the scheme could deliver water quality improvements by filtering flood water from the Alt through a series of reedbeds to trap out the pollutants which are currently causing the Alt to be failing its water chemistry standards.

The Alt catchment has been intensively farmed for many years and current practices are not sustainable; draining and ploughing of the peat soils expose them to the air and accelerate their degradation. In some areas the peat has been ploughed out and the sandy subsoil means farmers may have to change the crops they grow or cease farming altogether. A washland such as Lunt Meadows offers a method of preserving peat deposits and the potential to be an exemplar site for alternative farming practices in a catchment dominated by intensive arable and salad crops.

Further Information


Lunt Meadows is the second largest wetland in North Merseyside and the long term site management will create the conditions for an essential ‘stepping stone’ for wildlife within the agricultural plain, connecting nationally important wetlands in the region that are otherwise widely separated from each other.

During initial excavations, what is thought to be a stone-age settlement was discovered and ongoing recovery works have shown it is a site of national archaeological importance; one of only a handful where evidence of permanent settlement from over 8000 years ago still exist.

Contacts


Robert Ide, Environment Agency

enquiries@environment-agency.gov.uk

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