By Matthew Hatchwell and David Grzywacz
Pictures by Matthew Hatchwell and Tim Stonor
Anyone who has walked along the Westbrook between West Street and Chart Mill or near the footbridge between Beech Close and the Knole in recent years will have noticed the bundles of brushwood (“faggots”) that have been placed in some of the wider, slower flowing sections of the stream. The purpose of the faggot bundles is to concentrate the water into narrow channels whose more rapid flow prevents the accumulation of silt and helps to restore the original chalk stream character of the Westbrook.
The low flow channels in the Westbrook south of the West Street culvert have created a new island for nesting birds and other wildlife. Marsh marigolds abound, ringed here by flag irises
and thriving clumps of water starwort in the stream.
One of the features of chalk streams like the Westbrook is that, in their natural condition, they flow relatively fast over gravel beds that provide the ideal habitat for the wildlife species that make them so important for biodiversity. Changes made to the Westbrook over the centuries mean that the gradient of the streambed has been reduced and – especially in its lower reaches – a considerable volume of silt has accumulated. This has drastically altered the bed of the Westbrook with a build-up of silt and mud smothering the natural gravel bottom and driving out the unique chalk stream plants and animals it once supported. The problem of siltation has been compounded by the impact of water abstraction near the original course of the Westbrook south of Ospringe, which has reduced significantly the amount of water in the stream.
Only about 300 chalk streams exist in the world, most of them in southern Britain. They provide a unique but threatened habitat for a distinctive range of plants and animals and must be protected and restored wherever possible.
Ecological monitoring of the Westbrook shows that the area of highest biodiversity is the short gravel-bottomed section downstream from the Chart Mill where the water flows fastest. Caddis fly larvae, for example, which are characteristic of chalk streams and intolerant of silt, are relatively abundant in that gravelly section but absent from the heavily silted ones closer to Stonebridge Pond. Over time, low-flow channels in the stream will promote faster water flow, flushing out the silt and thus exposing the gravel streambed and enhancing biodiversity in the stream. The stream with its combination of faster meandering channels and still waters behind the faggots will create a wider mix of habitats enriching the stream’s diversity. Behind the faggots the still areas will become colonised by water plants such as marsh marigold, flag iris and water cresses binding the silt in these areas.
Ecological monitoring experts from the Environment Agency look for insects and other aquatic life in water samples from the Westbrook.
Chalk stream restoration and ecological monitoring on the Westbrook is led by the Friends of the Westbrook and Stonebridge Pond with support from a range of partner organisations. The Environment Agency has been particularly supportive in recent years, providing assistance to install eel passes on the sluices between Stonebridge Pond and Faversham Creek; funding to support the creation of low-flow channels in the Westbrook and to conduct a study of chalk streams along the north Kent coast (see Faversham Life, January 5, 2024); advice on using citizen science to monitor water quality in the Westbrook and Faversham Creek; and most recently by providing hands-on assistance to extend low-flow channels to new sections of the stream.
The work of the Friends was recognised in 2022 with a Queen’s Award for Voluntary Service, the equivalent for community organisations of an MBE for individuals.
An Environment Agency working party helps the Friends of the Westbrook and Stonebridge Pond install a new low-flow channel
Over time, faggot bundles rot down and need to be replaced. Silt and woody debris accumulate in areas of standing water behind the faggot bundles, plants take root, and a narrower, faster flowing watercourse emerges.
The same factors that caused the siltation of the Westbrook have created a similar problem in parts of Stonebridge Pond and surrounding channels, where the water is now just a few centimetres deep in some places overlying a thick layer of silt. In the past, any accumulation of silt was prevented by the regular flushing caused by the water mills that drove the gunpowder industry along the Westbrook and on the site of the Stonebridge allotments. The narrow channels or leats that crisscross the allotments were originally 2-3 metres deep, so the shallow layer of water hides a large volume of silt that will clog the system altogether unless action is taken soon. Removing all the accumulated silt and the possible contaminants that lie buried in it would be very costly. Consequently a number of other options are being explored that would protect Stonebridge Pond as a much-loved community amenity at the same time as allowing the restoration of the Westbrook as a globally important chalk stream.
An edited version of this article appeared on the Faversham Life blog (www.favershamlife.org) on March 8, 2024.
Faversham's waterways and the Westbrook stream from a map of 1896-8. Courtesy National Library of Scotland
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