Development of a catchment-scale
restoration strategy for the River Till,
Northumberland
Carolyn Mills and Hamish Moir
cbec eco-engineering UK Ltd.
River Till, Northumberland
Edinburgh
Berwickupon-Tweed
Northumberland
National Park
Newcastle
River Till restoration
River Till overview
• Part of River Tweed SSSI and SAC, important for a diverse range of
plant and animal species
• Currently in ‘unfavourable condition’, mainly as a result of physical
modifications.
Strategy to restore ‘favourable condition’ to the River Till required
River Till restoration
River Till overview
• Flows north from Cheviot Hills to join Tweed near Coldstream.
– Rural, agricultural catchment
– Character influenced by glacial deposits and Holocene terraces
• Pressures include:
– Extensive commercial gravel extraction during 20th Century
– Channel realignment and embankment construction
– Land management practices (overgrazing)
River Till restoration
Process-based approach to restoration
• Underlying principle is to restore natural geomorphic process to the
system as much as is practicable.
• Restoration measures must be appropriate to the broader scale
'geomorphic process regime' of the river.
• Ensures that benefits of restoration can be maintained with
minimal intervention over the long term
• Define reference state (how system
would behave under unimpacted
conditions)
• Identify how current modifications
impact on physical process
• Identify restoration measures that
will restore process closer to
reference state
River Till restoration
River Till restoration strategy - approach
Catchment scale approach
1. Develop detailed understanding of fluvial processes
Conceptual physical process model
2. Identify current impacts to physical process
Engineering and land use impact index
3. Determine most impacted locations
4. Develop prioritised restoration options
Maximise benefit from available
funding
Provide process-based context for
subsequent detailed restoration
design
River Till restoration
Data compilation
• Existing data sets compiled into GIS
–
–
–
–
Fluvial audits
EA flood banks
Aerial imagery
LiDAR
• Fluvial audit data standardised
• Targeted field surveys where data gaps identified
River Till restoration
Conceptual process model development
• Semi-quantitative analysis
– Robust basis for restoration recommendations
• Division of river into study reaches
• Indices of geomorphic process derived from data
– Specific stream power
– Sediment supply
– Sediment storage
• Historical analysis at selected locations
River Till restoration
Conceptual process model development
Specific stream power
Sediment
Sedimentstorage
input index
index
River Till restoration
Conceptual process model development
River Till restoration
Conceptual process model development
River Till restoration
Conceptual process model development
Geomorphic process intensity =
specific stream power * sediment storage index * sediment input index
Good correlation with historic channel migration (R2 = 0.89)
River Till restoration
Conceptual process model development
Geomorphic process regime
 Geomorphic process
intensity
 Dominant process
(supply, transport or
storage)
Indication of reach sensitivity
to pressures
River Till restoration
Engineering and land use pressure index
• Locations of engineering and land use pressures taken from GIS
database of field survey data
• Features grouped into categories and assigned weightings
according to severity of pressure
River Till restoration
Engineering and land use pressure index
River Till restoration
Reach impacts
Integration of reach
sensitivity with
pressure severity
Reaches assigned
impact severity class
(very low to very high)
Information about
nature of impacts
Used to identify and
prioritise restoration
recommendations
River Till restoration
Restoration recommendations
Matrix of options
• Degree of improvement to physical process
• Likely cost
• Constraints
Full socio-economic consideration and stakeholder consultation at a
later stage
River Till restoration
Summary
• Process-based, catchment-scale approach used to
develop restoration strategy for the River Till.
• Understanding of spatial variation in process gained from analysis of
sediment input and storage, specific stream power and historic analysis.
• Levels of impact determined from reach sensitivity and degree of pressures.
•
Provides set of recommended measures that are grounded in robust
analysis.
• Ensures that subsequent detailed restoration design is
undertaken in context of system and is physically appropriate.
River Till restoration
14TH ANNUAL NETWORK CONFERENCE
Scaling up our Aspirations for
River Restoration and
Management
The RRC would like to thank the sponsors of the RRC Annual Conference 2013
who support discounted places
rrc@therrc.co.uk
01234 752979
www.therrc.co.uk