Case study:Rottal Burn

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Location: 56° 48' 51.82" N, 3° 1' 46.29" W

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Project overview

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Status	Complete
Project web site
Themes	Fisheries, Habitat and biodiversity
Country	Scotland
Main contact forename	Nick
Main contact surname	Elbourne
Main contact user ID
Contact organisation	Esk Valley Trust
Contact organisation web site	http://www.eskvalleytrust.org/
Partner organisations
Parent multi-site project
This is a parent project encompassing the following projects	No

Restoration of the historic meandering channel

Project summary

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The reach of the Rottal burn between Rottal Lodge and its confluence with the South Esk has historically been realigned and straightened since the 1830’s. In 2003, just prior to the Water Framework Directive coming into force, the stretch was dredged out destroying the existing habitat. The works carried out in 2012 aimed to restore natural river processes and in stream and riparian habitat, specifically for Atlantic salmon and freshwater pearl mussel alongside other fish species. It is relevant to note that the freshwater pearl mussel is dependent on juvenile salmon populations for the completion of its life cycle.

Objectives of the project included: • Restoration of the canalised water course as far as possible to its natural course (to be extended from 650m to 1,100m) • Reconnection of the Rottal Burn with its flood plain • Creation of a diverse riparian and aquatic habitat including the incorporation of the existing wetland habitat into the final restoration design • Reduction in the unnaturally high sediment loading during high flow events which is then deposited in the lower reaches • A return to a more natural flow regime • Attenuation of flood peaks • Visual enhancement of the area • Restoration of sustainable, functional populations of multi-sea-winter salmon and trout and of freshwater pearl mussels • The possibility of transferring freshwater pearl mussels into the burn will be investigated • Development a demonstration site available for future research • Provision of restoration experience which would be transferable to other similar situations within the catchment

Construction works were designed to create the restored channel without any import or export of materials, by using existing gravel embankments to provide any material needed. Large woody debris (trees with rootballs) which were sourced from the local estate, were used to reinforce possible areas of adjustment. A two-phase construction programme was used; Firstly the new channel was constructed and vegetation growth allowed to take hold. Following this flow was diverted into the new channel. Challenges at the site included the remote location, adverse weather conditions and the presence of overhead services. A number of sediment bar features have already formed, significantly improving the habitat, which is confirmed by the presence of salmon spawning in the new channel.

Monitoring surveys and results

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Lessons learnt

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Catchment and subcatchment

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Catchment

River basin district	Sout Esk
River basin	South Esk

Subcatchment

River name	South Esk
Area category	100 - 1000 km²
Area (km²)	564 km²56,400 ha <br />
Maximum altitude category	200 - 500 m
Maximum altitude (m)
Dominant geology	Siliceous
Ecoregion	Great Britain
Dominant land cover	Grassland, Woodland
Waterbody ID

Other case studies in this subcatchment: South Esk restoration

Site

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Name	Rottal Burn
WFD water body codes
WFD (national) typology
WFD water body name
Pre-project morphology	Straightened, dredged (to remove gravels)
Reference morphology	Actively meandering (historic channel identified)
Desired post project morphology
Heavily modified water body	No
National/international site designation	EU - Special Area of Conservation
Local/regional site designations
Protected species present	Yes
Invasive species present	No
Species of interest	Atlantic salmon, The freshwater pearl mussel
Dominant hydrology
Dominant substrate	Gravel
River corridor land use	Rough unimproved grassland/pasture
Average bankfull channel width category
Average bankfull channel width (m)
Average bankfull channel depth category
Average bankfull channel depth (m)
Mean discharge category
Mean annual discharge (m³/s)
Average channel gradient category
Average channel gradient
Average unit stream power (W/m²)

Project background

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Reach length directly affected (m)	11001,100 m <br />1.1 km <br />110,000 cm <br />
Project started	2012
Works started	2012/04/01
Works completed	2012/08/01
Project completed
Total cost category	100 - 500 k€
Total cost (k€)
Benefit to cost ratio
Funding sources	SEPA Restoration fund

Cost for project phases

Reasons for river restoration

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Mitigation of a pressure	Historic straighteneing
Hydromorphology	Quantity & dynamics of flow, Channel pattern/planform
Biology	Fish
Physico-chemical
Other reasons for the project	Improvement of atlantic salmon and freshwater pearl muscle habitat

Measures

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Structural measures
Bank/bed modifications	Adding sinuosity, Bank re-grading, Decrease sedimentation, expansion of river bed on some parts of the river
Floodplain / River corridor	Floodplain reconnection, removal of embankments
Planform / Channel pattern	Creation of sinuosity
Other
Non-structural measures
Management interventions
Social measures (incl. engagement)
Other