General
National Id
United Kingdom_01
Site name
Belford Burn catchment, Northumberland
Summary
Measures to attenuate runoff were installed in the small Belford catchment, in northeast England, in order to reduce the risk of flooding to the village downstream. The installations involved a network of small measures to capture and delay runoff from the rural catchment, including detention basins and overland flow features, as well as sediment capture measures to improve water quality.
Light or indepth?
In-depth
The in-depth description of the case study
NUTS Code
Northumberland and Tyne and Wear
RBD code
UK03
Transboundary
0
Data provider
Katie Hill and Heather Williams, AMEC
Source(s)
NWRM(s) implemented in the case study
Longitude
-1.83175794041
Latitude
55.5986067185
Site information
Climate zone
cool temperate moist
Mean rainfall
750
Mean rainfall unit
mm/year
Average temperature
9
Mean runoff
400
Mean runoff unit
450 - 600 mm
Average runoff coefficient
0,4
Type
Case Study Info
Average slope range
5-10%
Vegetation class
Rural with predominantly pasture and cultivated grasslands.
Monitoring maintenance
Monitoring impacts effects
1
Monitoring location
In-Stream
Monitoring parameters
At the start of the project there was no hydrometry present within the catchment. The Environment Agency has installed a telemetered gauging station within Belford village for Flood warning purposes. In addition they have installed a tipping bucket rain gauge at a farm to help with flood warning predictions. Alongside this Newcastle university installed a raingauge and three flow gauging stations, which will help understand the impact of the features on the flood peak hydrograph as a flood moves through the catchment.
A grab sampling campaign began in 2009 to characterize the sediment and nutrient regime and identify locations contributing to elevated levels of agricultural diffuse pollution.
Four auto samplers were deployed at two online pond features, one upstream and one downstream of each feature. This was to understand if they were retaining sediments and nutrients during storm events.
A grab sampling campaign began in 2009 to characterize the sediment and nutrient regime and identify locations contributing to elevated levels of agricultural diffuse pollution.
Four auto samplers were deployed at two online pond features, one upstream and one downstream of each feature. This was to understand if they were retaining sediments and nutrients during storm events.
Monitoring upstream station
Monitoring was undertaken at locations directly upstream and downstream of some NWRM features.
Monitoring downstream station
Monitoring was undertaken at locations directly upstream and downstream of some NWRM features. There is a WFD monitoring location on the Belford Burn.
Performance
Performance impact estimation method
Laboratory
Performance impact estimation information
For some NWRM features direct comparisons were made pre and post implementation, and also upstream and downstream of individual measures. Impact assessments were undertaken at a number of the indivdiual measures using available observed data. Model interpolation was used to understand the effects of multiple measures using hydraulic modelling.
Design & implementations
Application scale
River
Installation date
2011
Performance timescale
< 1 year
Area (ha)
570
Design capacity description
For this site a suite of small NWRMs are operating in combination, with a total storage of 9-10,000 m3.
The following are approximate maximum storage capacities used on the Belford site, per individual feature:
Overland flow interception: 1000 m3
Online ditch features: 150 m3
Offline ponds: 3000 m3
Large woody debris: 150 m3
Opportunistic measure sites: 3000 m3
As an example, one of the off line ponds implemented (approximately equivalent to 60x20m rectangle) stores approximately 3mm of runoff for 0.74km2 (however it is noted that in some cases the storage capacity reduced over time due to sediment buildup, which is an important consideration for maintenance). A further example was a small 1.2m dam that stores 500m3 of flow.
The following are approximate maximum storage capacities used on the Belford site, per individual feature:
Overland flow interception: 1000 m3
Online ditch features: 150 m3
Offline ponds: 3000 m3
Large woody debris: 150 m3
Opportunistic measure sites: 3000 m3
As an example, one of the off line ponds implemented (approximately equivalent to 60x20m rectangle) stores approximately 3mm of runoff for 0.74km2 (however it is noted that in some cases the storage capacity reduced over time due to sediment buildup, which is an important consideration for maintenance). A further example was a small 1.2m dam that stores 500m3 of flow.
Max water retention capacity
10000
Max water retention capacity unit
m3/day
Basis of design
Relatively short, high-intensity rainfall events. 5-17 year return period
Constraints
These types of measures are most suited for rural headwater catchments. The benefits can most directly be seen in terms of flood protection for small settlements a short distance downstream, although will continue to have a cumulative benefit in the whole downstream catchment.
Modelling has indicated that the measures are most effective for short, high intensity rainfall events, which suggests that they could also be applicable in drier climates, where intense rainfall events are experienced. They are effective for managing overland flow runoff, so may be less suitable in groundwater-dominated areas (although even in those situations could still have benefit for high intensity events that generate overland flow).
Fish passage requirements can pose a constraint to the type of NWRM applied. Fish passage can be restricted by online structures (e.g. in stream dams) so they are more suited to small watercourses and ditches where fish passage is not important or the watercourse runs dry during the summer months.
Modelling has indicated that the measures are most effective for short, high intensity rainfall events, which suggests that they could also be applicable in drier climates, where intense rainfall events are experienced. They are effective for managing overland flow runoff, so may be less suitable in groundwater-dominated areas (although even in those situations could still have benefit for high intensity events that generate overland flow).
Fish passage requirements can pose a constraint to the type of NWRM applied. Fish passage can be restricted by online structures (e.g. in stream dams) so they are more suited to small watercourses and ditches where fish passage is not important or the watercourse runs dry during the summer months.
Favourable preconditions
The upstream characteristics of the watercourse (small channels) are ideal for implementation to these types of NWRM features as the scale of flows to be retained is not large and the size of the feature can be kept small, resulting in little loss of agricultural land
Crop rotation
n/a. Mainly pasture
Public consultation
1
Design contractual arrangement
| Arrangement type | Responsibility | Role | Comments | Name |
|---|---|---|---|---|
|
No information available
|
Design consultation activity
| Activity stage | Key issues | Name | Comments |
|---|---|---|---|
|
Design phase
|
Decision support tools were made availalble to the famers to understand the underlying issues and provide them with adequate knowledge to participate in formulating a solution
|
meetings
|
|
|
Other
|
Famers were taking photographs and videos during flood events of the NWRM during flood conditions.
|
Effectiveness understanding
|
|
|
Implementation phase
|
Field trips were organised for villagers to see the wrok being undertaken
|
Field trips
|
Design land use change
| Land use change type |
|---|
|
Land principally occupied by agriculture, with significant areas of natural vegetation
|
Design authority
| Authority type | Role | Responsibility | Name | Comments |
|---|---|---|---|---|
Lessons, risks, implications...
Key lessons
The implementation of the suite of 35 NWRM features within the Belford Burn has shown how a catchment plan was created that was effective at providing multi purpose benefits (including flooding prevention and water quality improvements). A variety of stakeholders were engaged in the work from identification of the problem to be addressed to the siting and implementation of the individual NWRMs. A challenge is to remain adaptable and flexible, changing materials or NWRMs used to suit specific site conditions, in some cases using existing natural features within the channel such as large boulders, trees and bends to assist with stream control without the need for in-channel structures. Although developed for Belford the approach has generic applicability to many other catchments. Key lessons identified are that:
- A number of NWRMs can be used together, with the materials, location and choice of feature being dependant on local factors including land owner/farmer preferences and local terrain.
- One single NWRM feature only has a small benefit and it is likely that a number may be required together, but this should not ignore the fact that other structural measures may also be beneficial.
- Online features are best suited to smaller channels.
- The effectiveness of networks of NWRMs to attenuate flood depends upon the shape of the hydrograph, often being more effective for flashy short duration flood events.
- Ongoing maintenance and the potential need to recover trapped sediment, which could be of value to famers.
- It is essential to engage stakeholders, as this will encourage uptake by farmers.
- It is crucial to build up the trust of farmers and residents from the earliest opportunity and maintain it throughout.
One important finding has been that different types of measures may be more effective for flood and water quality benefits. At this site, a range of measures has been incorporated in to the overall scheme and hence provides effectiveness for both flood management and water quality improvements (nutrients and sediment). However only using a single type of measure, rather than a range, may not have been so successful in this regard. The need to consider a range of measures distributed through the catchment, to meet multiple objectives, is clear.
- A number of NWRMs can be used together, with the materials, location and choice of feature being dependant on local factors including land owner/farmer preferences and local terrain.
- One single NWRM feature only has a small benefit and it is likely that a number may be required together, but this should not ignore the fact that other structural measures may also be beneficial.
- Online features are best suited to smaller channels.
- The effectiveness of networks of NWRMs to attenuate flood depends upon the shape of the hydrograph, often being more effective for flashy short duration flood events.
- Ongoing maintenance and the potential need to recover trapped sediment, which could be of value to famers.
- It is essential to engage stakeholders, as this will encourage uptake by farmers.
- It is crucial to build up the trust of farmers and residents from the earliest opportunity and maintain it throughout.
One important finding has been that different types of measures may be more effective for flood and water quality benefits. At this site, a range of measures has been incorporated in to the overall scheme and hence provides effectiveness for both flood management and water quality improvements (nutrients and sediment). However only using a single type of measure, rather than a range, may not have been so successful in this regard. The need to consider a range of measures distributed through the catchment, to meet multiple objectives, is clear.
Success factor(s)
| Success factor type | Success factor role | Comments |
|---|---|---|
|
Attitude of relevant stakeholders
|
main factor
|
Identification of a combined approach that was flexible and adapted to the local factors, and the willingness of the regulator to explore new approaches. |
|
Available support tools
|
main factor
|
Availability of the tools for non-expert stakeholders to appreciate and inform solutions |
|
Communication activities
|
secondary factor
|
Crucial in getting "buy -in" from land owners and famers to allow these features on the land |
|
Conducted assessments (incl. economic)
|
secondary factor
|
Interest in a catchment based approach and the requirement for monitoring and modeling investigations did not prevent the work going ahead, but ensured confidence in the outcomes of the work and further understanding of effectiveness of the NWRM approach. |
|
Attitude of the public
|
secondary factor
|
It helps greatly when there is good relationship between the community and farmers. |
Financing
| Financing type | Comments |
|---|---|
|
National funds
|
Environment Agency
|
|
Sub-national funds
|
Northumbrian Regional Flood Defence Committee
|
Driver
| Driver type | Driver role | Comments |
|---|---|---|
|
Past flooding events
|
main driver
|
Severe flood events in small settlements downstream caused this to be considered. The Environment Agency were the main driver behind this measure being implemented, looking for lower-cost solutions to enable protection of small communities where high capital expenditure could not be justified. Other 'normal'flood defence approaches failed cost benefit criteria for support, and would not be suitable within Belford due to shortage of space between the channel and nearby houses. The 'natural' approaches were financially viable for the site, and enabled storing and attenuating flows in the upstream area.
|
|
Other
|
secondary driver
|
Unsuitability of 'structural' measures in the area.
|
Financing share
| Financing share type | Share | Comments |
|---|
Policy, general governance and design targets
Policy description
Belford village has a long history of flooding, often causing damage to properties. An Environment Agency flood defence pre-feasibility study concluded that traditional flood defences were not suitable for Belford because of the high cost, lack of space for flood walls and banks, and the small number of properties at risk, resulting in an unfavourable cost-benefit assessment. There was a desire to deliver an alternative catchment based and more cost-effective solution to the problem. In addition to this, the waterbody is not at Good Ecological Status, and sediment retention and nutrient management as part of the NWRM programme will help to address this.
Quantified objectives
The main objective is to reduce flood risk to Belford village downstream. Some of the measures also contribute to sediment retention, which has the potential to contribute to the waterbody achieving good ecological status, and help towards maintaining the quality of the downstream SPA.
Part of wider plan
1
Policy target
| Target purpose |
|---|
|
Runoff control
|
|
Peak-flow reduction
|
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Increase Water Storage
|
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Pollutants Removal
|
Policy pressure
| Pressure directive | Relevant pressure |
|---|
Policy area
| Policy area type | Policy area focus | Name | Comments |
|---|
Policy impact
| Impact directive | Relevant impact |
|---|
Policy wider plan
| Wider plan type | Wider plan focus | Name | Comments |
|---|---|---|---|
|
Local
|
Water
|
Defence strengthening in Belford Village
|
This strategy was 1 of 3 strategies (including the NWRM measures implementation) where the Environment Agency funded investigation and strengthening wirk to be undertaken at the existing 'structural' flood defences within Belford Village.
|
|
Local
|
Urban
|
Sewer upgrade
|
This strategy was 1 of the 3 strategies (including the NWRM implementation) where Northumbrian Water upgraded sewers to improve the resiliance and prevent surface water flooding.
|
Policy requirement directive
| Requirement directive | Specification |
|---|
Socio-economic
Direct benefits information
There is no quantified information on the socio-economic benefits.
The use of a network of NWRMs in a rural landscape has provided a cost effective means to reduce flood risk downstream. Additional benefits include:
- Storing water in ponds on the fields removes sediment picked up by overland flow which can be returned to the farmer's field.
- Creating wetlands on some of the ponds provides new habitat for wildlife.
- The increased habitat and improved water quality is leading to an increase in the biodiversity in the catchment.
The use of a network of NWRMs in a rural landscape has provided a cost effective means to reduce flood risk downstream. Additional benefits include:
- Storing water in ponds on the fields removes sediment picked up by overland flow which can be returned to the farmer's field.
- Creating wetlands on some of the ponds provides new habitat for wildlife.
- The increased habitat and improved water quality is leading to an increase in the biodiversity in the catchment.
Costs investment
120000
Costs investment information
Construction costs only. 85,000 - 120,000 euros
Approximate costs per feature:
Barriers: €900-2,000 per m (dependent on material)
Woody debris: €120-1,200 per feature
Offline Ponds: €6,000 per feature (less if multiple ponds in close proximity)
Approximate costs per feature:
Barriers: €900-2,000 per m (dependent on material)
Woody debris: €120-1,200 per feature
Offline Ponds: €6,000 per feature (less if multiple ponds in close proximity)
Costs land acquisition information
No land aquisition was required as all measures were in-channel or on buffer strips, causing minimal disturbance to farmers' land.
Costs operation maintenance
Due to the nature of the NWRM, operational costs will be minimal, but there are maintenance requirements. There is also some additional cost associated with optimisation following implementation, e.g. Raising the outflow from a pond to increase its capacity
Costs operational information
Small costs are envisaged, but no quantative indication available. Management of features is done by combination of Environment Agency, Northumberland Rivers Trust and Natural England.
Costs maintenance information
Sediment clearance is important e.g. At sediment traps. Maintenance is also required of log/debris dams, which may need repairing or replacing over time
Costs disposal decommissioning information
Minimal costs
Compensations annual information
A one-off payment was made by the Environment Agency to famers for having access to the site for measure installation.
Information on Economic costs - income loss
There is some minor land loss associated with the construction of ponds. However any costs associated with this could be offset in part by benefits of sediment recovery and re-use. No quantification is avaialble
Ecosystem improved biodiversity
1
Information on Ecosystem improved biodiversity
Overall there is increased habitat for wildlife (water features), however the overall ecological performance is difficult to quantify and required further evidence.
Ecosystem provisioning services
1
Information on Ecosystem provisioning services
Minor loss of agricultural land for ponds, however in most cases these are usually located on field margins, in corners or in buffer strips to minimise impact.
Some benefits from re use of sediments that are removed from the NWRMs as part of the maintenance, although further investigation is required on the effectiveness and benefits of this.
Some benefits from re use of sediments that are removed from the NWRMs as part of the maintenance, although further investigation is required on the effectiveness and benefits of this.
Ecosystem impact climate regulation
Not relevant for the specific application
Biophysical impacts
Information on retained water
The estimated total for the suite of NWRMs is around 10,000 cubic metres in total.
Information on increased water storage
There was no storage previously.The estimated total for the suite of NWRMs is around 10,000 cubic metres in total.
Information on runoff reduction
Little net change in total runoff
Peak flow rate reduction
30
Peak flow rate reduction unit
%
Information on Peak flow rate reduction
An individual NWRM may only provide a very small reduction in the peak flow, but in combination larger peak flow reductions can be observed. This value is for a MODELLED system representative of Belford with total storage of 19,250 cubic metres, for the reduction of peak flow at the downstream end of the network of measures: 15-30% peak flow reduction.
Maintenance baseflow
0
Information on Increased infiltration
Possible increases in infiltration due to water being retained within the upper catchment for longer before flowing downstream.
Information on Increased Evapotranspiration
There is an increased extent of open water, but effects on evapotranspiration are likely to be insignificant since the retention times are low.
Ecosystem erosion control
0
Information on Ecosystem erosion control
Does not directly affect erosion, but does allow sediment to be captured and re-applied to fields, resulting in lower net loss
Water quality overall improvements
Positive impact-WQ improvement
Information on Water quality overall improvements
An investigation was begun in 2009 to assess effectiveness of features to reduce losses of sediment and nutrients. Parts of the catchment already had high concentrations of SS, P and NO3. The overall, cumulative impact of all the NWRMs has been found to be difficult to prove, and to require extensive monitoring. However some findings included:
- It was identified that online ponds were not retaining pollutants during the rising limb and peak of flood events.
- Overall conclusion was that online features are functioning to reduce chronic losses of Suspended solids but are less effective in storm events.
- Different features operate to retain pollutants under contrasting flow conditions.
The study area covers the upper 50% (approximate) of the associated WFD waterbody. Therefore it is likely that the improvements identified in water quality (e.g. phosphate) due the NWRMs will contribute to overall improvements in the Ecological status of the waterbody.
- A multi stage NWRM (constructed following findings of initial NWRMs) that included a sediment trap and willow barriers works effectively to reduce sediment and nutrient losses from the catchment during storms
- It was identified that online ponds were not retaining pollutants during the rising limb and peak of flood events.
- Overall conclusion was that online features are functioning to reduce chronic losses of Suspended solids but are less effective in storm events.
- Different features operate to retain pollutants under contrasting flow conditions.
The study area covers the upper 50% (approximate) of the associated WFD waterbody. Therefore it is likely that the improvements identified in water quality (e.g. phosphate) due the NWRMs will contribute to overall improvements in the Ecological status of the waterbody.
- A multi stage NWRM (constructed following findings of initial NWRMs) that included a sediment trap and willow barriers works effectively to reduce sediment and nutrient losses from the catchment during storms
Water quality Improvements Phosphorus (P)
26
Water quality Improvements (P) unit
% reduction pf pollutant
Information on Water quality Improvements (P)
Multi stage NWRM measured over a 24hour storm event. 26% TP reduction, 25% soluble RP reduction
Water quality Improvements Nitrogen (N)
15
Wq Improvements n unit
% reduction pf pollutant
Information on Water quality Improvements (N)
Multi stage NWRM measured over a 24hour storm event. 15% NO3 reduction
Water quality Improvements Total Suspended Solid (TSS)
40
Water quality Improvements (TSS) unit
% reduction pf pollutant
Water quality Improvements (TSS)
After a large runoff event a retention bund. Estimated 0.99 tonnes of sediment captured (retention bund)
Multi stage NWRM over a 24hour storm event. 40% SS reduction (multi stage NWRM)
Multi stage NWRM over a 24hour storm event. 40% SS reduction (multi stage NWRM)
Soil quality overall soil improvements
N/A info
Information on Soil quality overall soil improvements
No information available. Unlikely to be significant changes