Hitting the reset button

Hitting the reset button

Natural Heritage Project Officer Alex Jones writes about the importance of hitting the reset button on Coventry's River Sherbourne

As the Natural Heritage Project Officer for the Sherbourne Valley Project I have spent the last 9 months or so getting to know the River Sherbourne and working out the best ways of making it better for wildlife. Two things that I have been looking for are places to create or enhance wetland habitat and finding and logging the locations of weirs in the catchment and working out whether they could be removed.

Both of these issues have implications for the wildlife of Coventry. Coventry’s current lack of quality wetland habitat results in a lower overall biodiversity for the city, this is because wetland provides the perfect home for some of Britain’s most iconic species; otter, water vole, cuckoo and numerous specialist insects and plants. It also takes away a myriad of benefits to people.  Wetlands perform a vital role in the attenuation of water. To explain this simply, wetlands act like a sponge holding up water which can play a role in the alleviation of flooding. In addition to this, wetland habitats act as excellent areas for people to experience wildlife, with which come health benefits such as reduced levels of stress, depression and anxiety. According to the Wildfowl and Wetland trust ‘Blue Spaces’ provide greater health benefits than even green spaces

The presence of Weirs in a watercourse has negative effects on riverine wildlife too because weirs act as a barrier to the movement of species such as migrating fish to their spawning grounds in addition to causing a number of issues regarding the normal processes of a river. In short the presence of a weir (or in the case of the Sherbourne, many weirs) can prevent a river from behaving in the way it naturally would and providing its usual functions.

As part of my search for areas that the Sherbourne Valley Project could seek to improve in Coventry for Wildlife and People, I have been visiting all of the parks and green spaces in the catchment in addition to visiting each of the 19 weirs to look for potential. Given the current state of the Sherbourne, an urban river catchment described as ‘Heavily Modified’ by the Environment Agency and scoring as ‘Poor’ for ecology and ‘Failing’ for chemical pollution Under the Water Framework Directive (the system used in the UK and Europe to assess the health of rivers) I had anticipated this task not involving many pleasant strolls through the countryside; imagine my surprise when I performed my first site visits to Coundon Wedge to visit a weir on the North Brook.  

Coundon Wedge is already a great place to enjoy nature and a really special place to be able to visit within walking distance of Suburban Coventry. As an avid bird watcher I have been astounded by the site species list that I have managed to build up there over the last 9 months, of which some personal highlights have been Raven, Cuckoo, Skylark and of course the Coundon Parakeets. I can already see the potential for improvements for wildlife to the area.

The weir in North Brook is very interesting and offers the potential of an exciting approach to its mitigation and a rare opportunity to combine a weir mitigation project with meaningful habitat improvements. The North Brook as it runs through the wedge takes an unnatural right angled bend before a steep drop to the weir below.

Looking at old maps of Coundon wedge it becomes clear that the brook must have been modified at some point well over 100 years ago. The process of rerouting the brook all those years ago has created a wet ditch that runs through the fields adjacent to the current course of the brook; this is something that we would describe as a ‘Paleochannel’ - simply put this is the channel that the river originally ran through. The presence of this channel suggests that there may be the potential of returning the North Brook to its original course and if this can be achieved it will provide fantastic dual gains for this area of Coundon Wedge.

It will functionally remove the weir in this location from the watercourse and secondly (most excitingly) it will ‘wet up’ the fields and help already emerging marshy habitats to further develop providing a boost to habitats in the area and a larger, better area of wetland to establish, providing homes for wetland species and somewhere for local people to access and gain the benefits from exploring and enjoying the area. 

This approach is known as ‘Stage Zero Restoration’ the ‘Stage Zero’ refers to allowing the river to return to the first stage in its development and, once again, begin to behave like a river or brook should, having been left to develop naturally. I like to look at it as hitting the reset button for the North Brook; after well over 100 years of it being made to follow a course set out of it by human convenience it will be able to flow through the course that it cut for itself once more and restore the habitats of Coundon Wedge back to their former glories.