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Measuring the effectiveness of River Restoration - the Eddleston Water project

28 October 2015

Authors: Scott Mackenzie, Mike Thornton, Hugh Chalmers and Chris Spray

Introduction

Section events offer CIEEM members the opportunity to learn new skills from experts in their local area. An event looking at river restoration at a catchment scale was organised by the Scottish Section in partnership with the North East England Section and Tweed Forum. The event took place on the 28 October and focused on the restoration of the Eddleston Water, a meandering gravel river which is a tributary of the River Tweed; a Special Area of Conservation. CIEEM members from a variety of organisations including academics, charities and private organisations attended the day. Attendees spent the day visiting locations across the Eddleston catchment, seeing first hand the completed works on the river, with discussion and information from those involved in the restoration and management directly.

Site History and Selection

Eddleston Water is a 69sq kms catchment, flowing some 17 kms south to join the Tweed at Peebles. The river was subject to heavy management in the 19th century, with straightening of the watercourse, primarily to build a new road to Edinburgh leading to a loss of a third of its length, and increasing the risk of flooding downstream. The restoration project has the twin aims of improving the habitats of the degraded river and reducing the risk of flooding to local communities through the introduction of natural flood management (NRFM) techniques. In addressing these issues, the project meets obligations from the EC Water Framework Directive (WFD) and EU Floods Directive, as well as working to maintain sustainable livelihoods for the local farming community. At the start of the project in 2010 the ecological status of the waterbody was classified as being ‘bad’, largely due to hydromorphology.

The project is funded from a large variety of sources, including Scottish Government, the Scottish Environment Protection Agency (SEPA)’s restoration fund, the Scottish Rural Development Programme, commercial and business contributions, as well as grants and, crucially contributions from the land managers themselves. Chaired by SEPA, the project is managed by Tweed Forum, along with Scottish Government and Dundee University. Other partners include British Geological Survey, Forestry Commission Scotland, Woodland Trust, Scottish Natural Heritage, Tweed Foundation, Forest Carbon and landowners. It forms one of a number of projects and initiatives led by Scottish Government and SEPA to understand the effectiveness of river restoration for habitat improvement and flood risk reduction.

Partnerships

Hugh Chalmers MCIEEM of the The Tweed Forum, gave CIEEM members a look into the successes and challenges of the project. Crucial to the project’s success has been getting local stakeholders involved, particularly landowners who needed to grant permission to undertake the works on their land. They needed to be convinced of the project’s vision and allow areas of their land to be set aside, be subject to restoration works and then, ultimately to take on the responsibility of managing the area. Hugh’s background as an agricultural advisor in the local area was integral to this achievement, as is the wider role of Tweed Forum in establishing relationships with landowners and in building trust with all stakeholders involved.

Methods and Successes

The project began in 2010 with a scoping study by Dundee university to identify where and which forms of intervention (soft engineering) could be possible across the whole catchment. A number of these NFM techniques were then proposed to improve both the WFD status and to reduce flood risk. These techniques are not implemented everywhere along the catchment as land use and habitat types determine which method is used in any one location. For instance, in some tributaries, mire habitats dominate the flood plain, and therefore peat dams and appropriate tree planting have been used to restore peatland hydrology, in other locations debris dams have been introduced, whilst elsewhere the straightened river has been re-meandered.

These techniques were deployed in various parts of the catchment to hold up water, preventing flooding downstream. Re-meandering of the straightened river to slow flow and improve hydrological status has occurred in three lengths so far, with more in progress. This method required the construction of a new channel, as well as fish capture and, where necessary the transportation of both substrate and macrophytes from the original to the new channel. The approach led to an increase in river length by 150m, resulting in the formation of natural gravel bars, and the recreation of beds of macrophytes.

Another technique implemented in this scheme has been the placement of log jam flow restrictors, which are designed to allow fish passage up the river, but still hold water during flood events. Tree planting within the flood plain is another method which has been used to ensure the longevity of the improvements, with the vision of the trees falling into the streams in the future, forming natural flow restrictors long after other current methods deteriorate. Extensive tree planting along the river banks down stream of this area has also been implemented to retain water through intake and transpiration.

Monitoring and Going Forward        

Fundamental to the ethos of the whole project has been to measure the costs and benefits of all this work. Before any work started on the ground, a very detailed fluvial audit was undertaken by cbec ltd, and an extensive hydrological network of river gauges was put in place, along with weather stations covering the whole catchment. Individual interventions are also monitored and modelled, with the site of the main re-meander sections being the locations for very detailed hydro-morphological and matching ecological studies, using a BACI approach, with contrasting ‘control’ sections up and down stream. The Eddleston is now the most intensely monitored catchment in Scotland, with other studies on the fish, the macrophytes, the birds, the attitudes of farmers, the history and the detailed mapping of the catchment ecosystem services (both current and historical using air photos from the 1940’s).

The financial costs of all the work has been recorded as it progresses, as have the impacts of the different measures on the habitats and flood hydrographs. Already the river’s ecological status has improved from ‘bad’ through ‘poor’ to ‘moderate’ as a result of the restoration programme. Other work shows the time of peak flood levels can be reduced by over an hour and the floodplain hold greater amounts of water. In the long-term, the ultimate test for this project will be to understand to what extent the restoration work can mitigate against flooding events during periods of heavy and prolonged rainfall, and how the habitats recover. The project has received positive feedback throughout and has just won further support from the EU through a successful INTERREG bid, and it is hoped that its success will lead to this approach being implemented throughout Scotland and potentially the rest of the UK.

The Eddleston Water Project is managed by Tweed Forum and led by the project team of SEPA, Scottish Government and Dundee University, with partners including British Geological Services, Scottish Borders Council, Forestry Commission Scotland, National Farmers Union (Scotland), The Environment Agency, Scottish Natural Heritage, Tweed Foundation, Forest Carbon, Woodland Trust, local businesses and, especially local landowners.

 

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