The proposal is to open up the 280m Moorlands Road culvert by creating a meandering channel with backwaters (to temporarily store flood water) including a variety of in-stream habitat, seeding species rich meadow mix on the banks and tree planting and making improvements to the public access of the site.

 

Culvert proposal

The Merriott catchment which is currently classified as having poor ecological status, because of low fish numbers due to little available fish habitat, barriers to fish migration and historic pollution events. One such barrier is a 300m-long culvert between the flood alleviation scheme and the mill house near Moorlands Road. We are proposing to open up the culvert and restore an open meandering stream with habitat and flood attenuation features as well as provide fish passage easement thought the Merriott flood alleviation scheme.

The culvert field flooded in roughly the location where the new channel would be

Detailed design

The detailed construction design was drawn up by Ghyston Engineering and Hydro-Morph and includes:

  • Cross sections and long sections defining the meandering channel allowing fish passage, floodplain connection and including suitable substrate for habitat creation and erosion reduction.
  • Engineered step-pool ramps that gently lower the stream bed from the alleviation dam to the open channel at the upstream end as well as from the open channel back into the culvert at the downstream end—passable for native fish.
  • A number of backwater areas to provide flood storage and wetland habitat.
  • Engineering drawings for a ford to allow for vehicle and livestock crossing. Construction phases, instructions to contractors, utilities and health and safety considerations.
  • Planting and habitat creation plan including securing logs in the stream, tree planting on the banks and seeding a diverse meadow mix on disturbed ground.

The overview design plan can be viewed by clicking here.

 

Proposed public access improvements

The current footpath will be improved by: 1) levelling and spreading stone on the surface towards the Flood Alleviation Dam and 2) removed the hedge on the culvert side in places of low habitat value, which will widen the footpath, improving the view of the field and removing the current ‘tunnel feel’ and allowing use of the footpath in all weathers.

The landowner is offering to create a permissive path through the field along the northern boundary of the stream so that walkers can enjoy the newly created wildlife areas. Please enjoy the field responsibly and adhere to the permissive path. A permissive path is granted by the landowner rather than it being a statutory right and the landowner has the right to remove a permissive path. The map below shows the suggested improvements.

The map below shows the line of the permissive path, and click here for details on the planned improvements on the existing public footpath.

 

Flood risk modelling

Flood risk modelling was contracted out to Edenvale Young. For flood events between 1 in 2 and 1 in 100 year storm events, the models predicted flood reduction. The functioning of the alleviation dam, protection for events up to 1 in 25 years, remains unaffected. For extreme flood events (those in excess of 1 in 100 years when the existing flood alleviation dam would be overwhelmed and Merriott already flooded) the model predicts a nil effect with possible minor increases in depth in certain areas (up to a maximum of 4cm flood depth on top of the baseline flood depth of >0.5m) and respective decreases elsewhere. Please note that the model’s inaccuracy level is ±2cm.

 

Planning Application and Consensts

Planning Application was submitted in May, you can view the planning application including all engineering drawings by clicking here. We are expecting the decision latest mid September 2020.

An application for Ordinary Watercourse Consent has also been submitted with the Somerset County Council.

 

Preliminary ecological surveys

We carried out preliminary ecological surveys and the current guidance from the planners is that no further surveys are required. The grassland is semi improved with a few areas that are species rich, which will be avoided during construction. The hedge between the footpath and the culvert field is mainly made up of non-native or non-valuable species. The few isolated bushes of spindle and dogwood in the hedge, as well as all other trees on site, will be retained. The site provides suitable habitat for reptiles like slow worms and grass snakes. Phased strimming will encourage reptiles out of construction areas. Whilst the potential of bats using the culvert was assessed as low, we are organising an emergence survey. Construction may mean a temporary loss of habitat for bats, but the scheme will overall enhance the habitat. The site currently is not suitable for water voles and otters, and there is no evidence of badger activity.

 

Funding

The Merriott project is funded by a scheme under the Rural Development Programme for England (RDPE – EU funding) called the Water Environment Grant (WEG). The scheme is being designed to support delivery of projects to improve ecological status of rivers in England. The Merriott project attracted the funding because of its poor ecological status. The UK was underspent in the RDPE budget from the EU. If the remaining budget is not spent, it would have to be sent back to the EU.

The original development of this project was funded through the Hills to Levels Multiple Benefits Project, a partnership project between FWAG SW and the Environment Agency, funded by the Environment Programme (Water Environment Improvement Fund WFD GiA).

View from the Flood Alleviation Dam in high flows

 

Community Engagement

Three articles were published in the Merriott Messenger which goes out to all households in Merriott. The first article, in autumn 2018, introduced the project and invited to a community event held in Merriott village hall on 24th September with more than 40 members of the public attending. The second article, in autumn 2019, discussed the results from the Flood Risk Modelling and again invited to a community event held at the Kings Head Pub on 18th November 2019. A third article, summer 2020, is updating on progress such as the detailed design, planning and footpath improvements.

 

Monitoring and view to the future

Whilst the funding ends, post construction and the management responsibility falls to the riparian landowners. FWAG is not planning to walk away from the site, but to monitor the site and provide ongoing habitat management advice. Monitoring will include:

  • Assessing which species develop on the site
  • Understand / map the stream’s natural evolution: use drone footage and cross sections before, during and after construction, after the first winter etc
  • Monitoring water levels in the channel and backwater areas to check whether they temporarily store flood water on the floodplain
  • Assessing whether adaptive management is required and securing funding for those

Looking to the future, we are hoping this site will be suitable to attract maintenance funding through the Government’s Environmental Land Management Scheme (ELMs). The schemes vision is to provide public funding for public goods, in this case thriving plants and wildlife, flood attenuation and beauty and engagement with the environment.

This project is part of a wider catchment initiative which is looking at removing further barriers to fish migration to allow migration between the two tributaries of the Merriott and potentially reintroducing brown trout form the Parrett into the upper catchment to re-establish sustainable populations.

 

Thank you to all landowners involved: for their time, effort, and cooperation and for giving up land, and to anyone else who has helped this project to progress.

For further information contact Sabine McEwan on 07769321135 or [email protected]