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.
Trang 1Issue 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
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
Riverbank protection works have multiple benefits, for instance the
DEFRA Farming and Watercourse Management Handbook Section 7
(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
• 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
Clifton-on-Bowmont
Sustainable Riverbank Protection
Trang 2Clifton-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
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
This work requires a minimum of Registration level
authorisation from SEPA and SSSI consent from SNH
Site one before works Site one after works
Costs
Total cost (net costs)
= £3,274 Cost per linear metre
= £94
Site two – Filtrexx approach
Detail
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
This work required a Simple Licence level of
authorisation from SEPA
Site two before works Site two after works
Costs
Total cost (net costs)
= £14,885 Cost per linear metre
= £186
Site three – willow spiling
Detail
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
This work required a Simple Licence level of
authorisation from SEPA Site two before works Site two after works
Costs
Total cost (net costs)
= £10,725 Cost per linear metre
= £134
Site four – engineered logjam
Detail
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
This work did not require authorisation from SEPA
but did need separate SSSI consent from SNH Site four before works
* More photos are available at: www.cheviotfutures.co.uk
Site four after works
Costs
Total cost (net costs)
= £3,400 Cost per linear metre
= £97
Case Study