Erosion is one of many natural river processes. Problems arise where the rate of erosion is considered too rapid to be acceptable and can be problematic for a number of reasons, for instance loss of valuable agricultural land, risk to local infrastructure and sedimentation downstream.
Sustainable Riverbank Protection Clifton-on-Bowmont, Scottish Borders Erosion is one of many natural river processes Problems arise where the rate of erosion is considered too rapid to be acceptable and can be problematic for a number of reasons, for instance loss of valuable agricultural land, risk to local infrastructure and sedimentation downstream In upland areas it is often the case that river floodplains, or haughlands, are the most productive land available to a farm business For example the haughland at Clifton-on-Bowmont is currently used for arable crops and is the most productive, and valuable, land on the farm and in the valley Land managers can lose large amounts of their high productivity land to riverbank erosion which can have significant detrimental impacts upon a farm business A loss of such land may mean that a farm business could lose arable fields, as outlined in this case study, or land of high value used for grazing and lambing etc, thus having an economic impact on the business Taking action against riverbank erosion can mean an increase in business resilience in economic terms, whilst also helping a farm business become more resilient to climate change It is predicted that severe storms will become more regular, making aggravated riverbank erosion more likely in the future • Reduction of channel widening that results in shallow flows, especially in summer, which can cause increases in water temperature and reductions in oxygen levels, leading to fish mortality • Development of stable banksides creates habitat for mammals and birds as well as river bank vegetation The more rapidly vegetation can be established on newly stabilised banks, the better The aim of this demonstration site is to trial different bank protection techniques to help inform those interested in implementing such work Riverbank protection works have multiple benefits, for instance the DEFRA Farming and Watercourse Management Handbook Section (available online) states that the additional benefits of erosion control are; • Stabilisation of river banks reduces loss of agricultural land • Reduction of unwanted deposition in other areas • Reduction of excessive sedimentation within watercourses, which silts up gravel beds and destroys spawning and invertebrate habitat Clifton-on-Bowmont Issue Date: November 2012 Contacts: Jennifer Hewitson Northumberland National Park Authority | Tel: 01669 622 071 Tracy Hall Tweed Forum | Tel : 07824 197 016 www.cheviotfutures.co.uk | E-Mail: info@cheviotfutures.co.uk Case Study Clifton-on-Bowmont, in the Scottish Borders, has a number of sections of eroding riverbank, which are presenting a number of management issues to the farm business and also threatening vital local infrastructure The sites have been identified through the innovative Farm Resilience Plan approach, which is being undertaken with individual farm holdings by Cheviot Futures As part of the resilience planning the land manager considered the cost implications of both completing and not completing the work in order to come to an informed decision with regard to taking the work forward Cheviot Futures is implementing a range of green bank protection measures on the site, to act as a demonstration opportunity to compare and contrast the merits (or otherwise) of different approaches This work was supported by a site-specific consultants report This work required authorisation from SEPA (Scottish Environment Protection Agency) and consent from SNH (Scottish Natural Heritage), which is an important consideration when researching similar work on any holding (similar authorisations are required from Environment Agency in England and Natural England) SEPA CAR Authorisation Costs (2012 fees) • Registration level activities £104 (paper application) • Simple Licence activities £594 It is important that a farmer weighs up the cost of implementing such work against the cost implications if no work was completed The section below aims to give detail of four types of riverbank protection being trialled at Clifton-on-Bowmont, including project description, costs and consents required Site one – timber revetment design Detail Costs 35m length of bank protected using a timber revetment design, using vertically piled timbers backfilled with local material and live willow, held in place by hessian Total cost (net costs) = £3,274 Cost per linear metre = £94 This work requires a minimum of Registration level authorisation from SEPA and SSSI consent from SNH Site one before works Site one after works Site two before works Site two after works Site two before works Site two after works Site four before works Site four after works Site two – Filtrexx approach Detail Costs 80m of bank protected using the innovative Filtrexx approach, utilising compost filled socks, pre-seeded with native riparian grasses to facilitate early re-vegetation of the riverbank The work comprises a two to three layer terrace of filled socks, secured using enhanced specification platypus anchors and wooden stakes Total cost (net costs) = £14,885 Cost per linear metre = £186 This work required a Simple Licence level of authorisation from SEPA Site three – willow spiling Detail Costs 80m of bank protected using an enhanced specification of willow spiling work, creating a living barrier of woven willow The technique employs a two tier terrace, with timber toe protection alongside tightly woven native willows plus planted willow material Total cost (net costs) = £10,725 Cost per linear metre = £134 This work required a Simple Licence level of authorisation from SEPA Site four – engineered logjam Detail Costs 35m of bank protected using an engineered logjam approach using vertical and horizontal timbers piled into the ground and secured together with mild steel rods, with backfill comprising locally won sediment, brash and living willow material Total cost (net costs) = £3,400 This work did not require authorisation from SEPA but did need separate SSSI consent from SNH Cost per linear metre = £97 * More photos are available at: www.cheviotfutures.co.uk