General
National Id
United Kingdom_02
Site name
River Quaggy, South East London
Summary
River restoration and flood management measures were implemented on the River Quaggy in London. The measures were necessary due to increasing urban development in the river valley and natural flood plain, with an associated increase in fluvial flooding. A suite of measures was implemented between 1990 and 2005, including de-culverting a reach of river and creating associated floodplain; building a detention basin; set-back flood defences; channel re-profiling. This scheme took a catchment-scale view in order to develop the best solution, and worked with a multi-disciplinary team as well as having extensive community involvement.
The in-depth description of the case study
NUTS Code
Inner London
RBD code
UK06
Transboundary
0
Data provider
Heather Williams and Katie Hill, AMEC
Source(s)
NWRM(s) implemented in the case study
Longitude
0.030134
Latitude
51.455042
Site information
Climate zone
cool temperate moist
Mean annual rainfall
600 - 900 mm
Mean rainfall unit
mm/year
Mean runoff unit
450 - 600 mm
Type
Actual Test Site
Light or indepth?
In-depth
Mean annual runoff range
150 - 300 mm
Average slope range
2-5%
Vegetation class
Predominantly urban: hardstanding with grass turf in some areas
Monitoring maintenance
Monitoring impacts effects
1
Monitoring location
In-Stream
Monitoring parameters
A number of parameters were monitored during different stages of the scheme.
Prior to construction, eleven baseline surveys were carried out including surveys of riverine flora, trees, bats, fish, invertebrates, birds and mammals to inform designs in progress and enable the process of environmental impact assessment.
Water Quality and Sediment sampling was also undertaken during the work.
Socio economic surveys have been undertaken since the completion of the scheme to monitor visitor numbers to the site follwoing the NWRM implementation. Other Social, economic and heath studies have been undertaken.
Prior to construction, eleven baseline surveys were carried out including surveys of riverine flora, trees, bats, fish, invertebrates, birds and mammals to inform designs in progress and enable the process of environmental impact assessment.
Water Quality and Sediment sampling was also undertaken during the work.
Socio economic surveys have been undertaken since the completion of the scheme to monitor visitor numbers to the site follwoing the NWRM implementation. Other Social, economic and heath studies have been undertaken.
Monitoring upstream station
An existing monitoring point, located at Manor Park, was used between 1993-1995.
The scheme was implemented pre-WFD, but for maintenance monitoring , standard monitoring points associated with the WFD are now used.
The scheme was implemented pre-WFD, but for maintenance monitoring , standard monitoring points associated with the WFD are now used.
Monitoring downstream station
Up until 1994 there was a Water Quality monitoring site at the bottom of the Quaggy at Lewisham High Street.
The scheme was implemented pre-WFD, but for maintenance monitoring , standard monitoring points associated with the WFD are now used.
The scheme was implemented pre-WFD, but for maintenance monitoring , standard monitoring points associated with the WFD are now used.
Performance
Performance impact estimation method
Laboratory
Performance impact estimation information
A number of surveys and studies were undertaken to understand the performance of the scheme.
Design & implementations
Application scale
River
Installation date
2005
Performance timescale
Immediate
Area (ha)
1750
Area subject to Land use change or Management/Practice change (ha)
7
Size
4300
Size unit
m
Design capacity description
The overall River Quaggy Scheme provides flood protection for a minimum of a 1 in 70 year event.
Sutcliffe park floodplain has capacity for 85,000m3 of flood water
Weigall Road detention basin has capacity for 65,000m3 of floodwater, and the inflow maximum is designed for a 1 in 70 year flood event,
Sutcliffe park floodplain has capacity for 85,000m3 of flood water
Weigall Road detention basin has capacity for 65,000m3 of floodwater, and the inflow maximum is designed for a 1 in 70 year flood event,
Basis of design
Weigall Road:The overall design aim was to achieve a 1 in 70 year level of flood protection
Constraints
These NWRMs are suitable to be used within any urban environment, however will be limited to sites where suitable green areas are available (although some measures can be very flexibly incorporated, for example within gardens). Re-meandering a channel and creation of a detention basin are constrained by the avaialbility of land of a size suitable.
Favourable preconditions
Sutcliffe Park: the existing watercourse was culverted underground, and provided the ideal oportunity for flood risk management that would combine with river restoration, with existing recreational ground providing a suitable environment.
The urbanised nature of the Quaggy catchment and the direct implications to residential properties and local amenities results in a community that was ready to be involved.
The channels at the back of residents houses downstream of Manor Park are heavily tree lined, and so previous approach of raising the concrete channel wall was deemed unsuitable due to the resultant loss of the trees. A alternative was required,with political desire for storage rather than tree loss, and therefore set back defences were used instead.
The urbanised nature of the Quaggy catchment and the direct implications to residential properties and local amenities results in a community that was ready to be involved.
The channels at the back of residents houses downstream of Manor Park are heavily tree lined, and so previous approach of raising the concrete channel wall was deemed unsuitable due to the resultant loss of the trees. A alternative was required,with political desire for storage rather than tree loss, and therefore set back defences were used instead.
Peak flow rate
5
Design contractual arrangement
| Arrangement type | Responsibility | Role | Comments | Name |
|---|
Design consultation activity
| Activity stage | Key issues | Name | Comments | |
|---|---|---|---|---|
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Design phase
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Before construction meeting and stakeholder involvement
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In the case of the area downstream of Manor Park residents were involved in the designing of the defences put in place in their gardens
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Implementation phase
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During construction meeting and stakeholder involvement
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Implementation phase
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Progress meeting to say how its developing
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Other
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Getting people involve in the 'soft' works
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Schools, community groups etc were involved in soft works - e.g. Bird boxes.
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Design land use change
| Land use change type |
|---|
Design authority
| Authority type | Role | Responsibility | Name | Comments | |
|---|---|---|---|---|---|
Lessons, risks, implications...
Key lessons
The implementation of a number of NWRM within an urban environment has shown how effective measures can be implemented within an already constrained environment, that provides multiple benefits to the environment and local residents. Although developed specifically for the River Quaggy the approach has generic applicability to many other catchments. Key lessons identified are that :
- Communication and a positive attitude are key for this type of project. Early consultation is important as well as continued consultation. This includes active residents/ stakeholder engagement and involvement during design and construction including partnerships, schools and groups, as it not only ensures comprehension of the work but following implementation ensures a feeling of "ownership" and responsibility that continues for the length of the NWRM lifespan. A full-time public liaison officer was employed during the planning and implementation phases
- Design involved multi disciplinary teams of engineers, architects etc that all contributed their specialties to the Quaggy project ensuring visual, social and ecological enhancements were optimised at the same time as managing the flood risk.
- Taking a catchment-scale approach allows greater overall improvement and enabled some measures that could not have been implemented in isolation.
- Communication and a positive attitude are key for this type of project. Early consultation is important as well as continued consultation. This includes active residents/ stakeholder engagement and involvement during design and construction including partnerships, schools and groups, as it not only ensures comprehension of the work but following implementation ensures a feeling of "ownership" and responsibility that continues for the length of the NWRM lifespan. A full-time public liaison officer was employed during the planning and implementation phases
- Design involved multi disciplinary teams of engineers, architects etc that all contributed their specialties to the Quaggy project ensuring visual, social and ecological enhancements were optimised at the same time as managing the flood risk.
- Taking a catchment-scale approach allows greater overall improvement and enabled some measures that could not have been implemented in isolation.
Success factor(s)
| Success factor type | Success factor role | Comments | |
|---|---|---|---|
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Communication activities
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secondary factor
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Attitude of the public
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secondary factor
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Surveys have shown that there has been increased usage of the park following implementation |
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Public participation
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secondary factor
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Involvement of the residents etc in the "soft works" e.g. Bird boxes and the design of set back defences in residences gardens downstream of Manor Park. |
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Existing staff and consultant knowledge
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secondary factor
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A multidisciplinary team of engineers, landscape architects, and ecologists worked on the design to ensure that opportunities for major visual, social and ecological enhancements were optimised at the same time as managing the flood risk |
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Other
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secondary factor
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Formation of groups e.g. Local residents groups to bring people together but also act on local issues before they become a problem (e.g Japanese knot weed removal.) |
Financing
| Financing type | Comments | |
|---|---|---|
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National funds
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Environment Agency
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Local funds
|
Whilst the majority of works were financed by the Environment Agency, some of the river restoration works were funded through local partnership funding
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Driver
| Driver type | Driver role | Comments | |
|---|---|---|---|
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Public pressure
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main driver
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The was a public and political desire to have a flood storage area, to ensure that the trees downstream of Manor Park were safeguarded.
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Past flooding events
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main driver
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Flooding events occuring with an existing culverted channel meant that an alternative solution had to be found.
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Financing share
| Financing share type | Share | Comments |
|---|
Policy, general governance and design targets
Policy description
As urban development in the River Quaggy river valley and natural flood plain, near Lewisham in central London, is increasing, fluvial flooding experienced by local residents and businesses has increased. In 1968 the centre of Lewisham flooded to a depth in excess of 1m, and more recent flood events have occurred. A flood alleviation scheme was required that would ensure minimal loss of the remaining floodplain within the catchment.
Quantified objectives
The scheme reduces flood risk to 600 homes and businesses.
Part of wider plan
0
Policy target
| Target purpose | |
|---|---|
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Increase Water Storage
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Peak-flow reduction
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Oher Societal Benefits
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Improved Biodiversity
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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 | |
|---|---|---|---|---|
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Other plans, such as catchment flood managment plan have been implimented since the NWRM was implimented.
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Policy requirement directive
| Requirement directive | Specification |
|---|
Socio-economic
Direct benefits information
Sutcliffe Park: Throughout the project there has been a Community Liaison Officer, employed by the Environment Agency, to link with the local people and particularly the local schools, youth groups and residents' groups. There are many opportunities within the park for community projects, during implimentation and following. E.g. locallised invasive species and sedimentation issues have since been spotted and acted on so not a concern.
The network of boardwalks, pathways and viewing points at Sutcliffe Park were designed to encourage access to the river and ponds, all of which were an integral part of the scheme for community and wildlife enhancements, and there has been a subsequent 73% increase in the number of visitors.
Restoration of the original route of the river will encourage a natural environment to re-establish.
The local community has had real and lasting input to the scheme and will have the opportunity to influence management of the park in the future. Working alongside the community to develop spaces has been one of the most important aspects of the scheme. And lots of people have got involved.
The network of boardwalks, pathways and viewing points at Sutcliffe Park were designed to encourage access to the river and ponds, all of which were an integral part of the scheme for community and wildlife enhancements, and there has been a subsequent 73% increase in the number of visitors.
Restoration of the original route of the river will encourage a natural environment to re-establish.
The local community has had real and lasting input to the scheme and will have the opportunity to influence management of the park in the future. Working alongside the community to develop spaces has been one of the most important aspects of the scheme. And lots of people have got involved.
Ancillary benefits information
Local people have an improved out-door environment which benefits their health and well being
Costs investment
14700000
Costs investment information
This excludes consultancy fees.
Total approximately €14,700,000
Sutcliffe Park and John Roan School site: €4,700,000 to construct
Weigall Road and Eltham Palace Road: €2,600,000 to construct
Downstream of Maor park flood defences: €7,200,000
Total approximately €14,700,000
Sutcliffe Park and John Roan School site: €4,700,000 to construct
Weigall Road and Eltham Palace Road: €2,600,000 to construct
Downstream of Maor park flood defences: €7,200,000
Costs operation maintenance
There are operational and maintenance costs accociated with the scheme
Costs operational information
Operation is required of sluices during flood conditions.
During flood events park gates to be locked and to remain locked whilst park is flooded, and warning notices to be posted at park entrances to advise the public why the park is closed.
As flood waters subside, litter picking is required of the entire flood storage area and clearing of excess debris from habitat areas and structures and clearing excess silt from all areas is required. These are all required to ensure full effective operation of the scheme during subsequent flood events. No information is provided on costs associated with this.
During flood events park gates to be locked and to remain locked whilst park is flooded, and warning notices to be posted at park entrances to advise the public why the park is closed.
As flood waters subside, litter picking is required of the entire flood storage area and clearing of excess debris from habitat areas and structures and clearing excess silt from all areas is required. These are all required to ensure full effective operation of the scheme during subsequent flood events. No information is provided on costs associated with this.
Costs maintenance information
Maintenance is now undertaken by the associated Borough of the Park. For example London Borough of Greenwich for the Sutcliffe site.
Sutcliffe Park: flow control structures within the park have been designed to be maintenance free but channel widths and depths are to be maintained, with 1 visit every 10 years and Annual inspections of vegetation within channels. Similar long term managment approaches are used for the grasslands, wetlands and lake within Sutcliffe park.
Sutcliffe Park: flow control structures within the park have been designed to be maintenance free but channel widths and depths are to be maintained, with 1 visit every 10 years and Annual inspections of vegetation within channels. Similar long term managment approaches are used for the grasslands, wetlands and lake within Sutcliffe park.
Costs disposal decommissioning information
No information provided
Compensations annual information
No known payments made.
Compensations nr beneficiaries information
There were no financial benificaries
Ecosystem improved biodiversity
1
Information on Ecosystem improved biodiversity
Overall there is increased habitat for wildlife (water features), and Sutcliffe Park is now a local nature reserve.
Ecosystem provisioning services
0
Information on Ecosystem provisioning services
Unlikely to be a signficant effect
Ecosystem water supply
0
Information on Ecosystem water supply
Unlikely to be a signficant effect
Ecosystem impact climate regulation
Not relevant for the specific application
Biophysical impacts
Information on increased water storage
The scheme has introduced approximately 150,000m3 of flood storage
Information on Peak flow rate reduction
An individual NWRM may only provide a low reduction in the peak flow, but in combination larger peak flow reductions can be observed. The standard of flood protection for the River Quaggy has been improved from 1 in 5 years (20% probability) to a minimum of 1 in 70 years (1.4% probability).
Maintenance baseflow
0
Information on Ecosystem flood control volume
The increase in floodplain within Sutcliffe Park, and the storage capacity of the detention basin will result in reduced peak flows, as water will be slowed and contained in the upper part of the River Quaggy catchment for longer.
Information on Increased landscape storage capacity
Approximately 150,000m3 flood water storage. The increase in floodplain within Sutcliffe Park, and the storage capacity of the detention basin will result in reduced peak flows, as water will be slowed and contained in the upper part of the River Quaggy catchment for longer.
Ecosystem erosion control
0
Information on Restoring hydraulic connections
The connectivity between the River Quaggy and its floodplain has been restored within Sutcliffe Park by removing the watercourse from its underground culvert, and improving associated floodplain capacity. The use of set-back defences downstream of Manor Park has reconnected the watercourse to floodplain area adjacent to the channel
Water quality overall improvements
N/A info
Information on Water quality overall improvements
No information available, as the NWRM scheme started prior to WFD implementation, and information from the Environmental Assessment is not avaialble.
2009 WFD data indicates that the River Quaggy is of Poor Ecological Potential.
2009 WFD data indicates that the River Quaggy is of Poor Ecological Potential.
Soil quality overall soil improvements
N/A info
