Restoring the River Quaggy in London, UK

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
Longitude
0.030134
Latitude
51.455042
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 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.
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.
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.
Performance impact estimation method
Laboratory
Performance impact estimation information
A number of surveys and studies were undertaken to understand the performance of the scheme.
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,
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.
Peak flow rate
5
Design consultation activity
Activity stage
Design phase
Name
Before construction meeting and stakeholder involvement
Comments
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
Activity stage
Implementation phase
Name
During construction meeting and stakeholder involvement
Activity stage
Implementation phase
Name
Progress meeting to say how its developing
Activity stage
Other
Name
Getting people involve in the 'soft' works
Comments
Schools, community groups etc were involved in soft works - e.g. Bird boxes.
Design authority
Role
Financing
Name
Environment Agency
Comments
Implementation; co-ordination; financial
Name
Quaggy Waterways Action Group
Comments
Support for the scheme, implimentation
Authority type
Private property owners
Role
Initiation of the measure
Name
Land owners
Comments
Provision of land; support for scheme
Role
Implementation
Name
Breheny Engineering
Authority type
Other
Role
Other
Name
London Borough of Greenwich
Comments
Borough Council : Provision of land and subsequent maintenance of Sutcliffe park. The implimentation has direct impacts on their park.
Role
Determination of design details of the measure
Name
Halcrow Group Ltd
Comments
Design consultant on Sutcliffe park
Role
Implementation
Name
Alfred McAlpine
Comments
Construction work at Sutcliffe park
Name
London Borough of Sutton
Comments
Provision of Land as the implimentation has direct impacts on their park. Subsequent maintenance responsibilities.
Role
Other
Name
Community Groups
Role
Other
Name
Quaggy Group (Thames 21)
Comments
Clearance and maintenance
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.
Success factor(s)
Success factor type
Communication activities
Success factor role
secondary factor
Success factor type
Attitude of the public
Success factor role
secondary factor
Comments

Surveys have shown that there has been increased usage of the park following implementation

Success factor type
Public participation
Success factor role
secondary factor
Comments

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.

Success factor type
Existing staff and consultant knowledge
Success factor role
secondary factor
Comments

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

Success factor type
Other
Success factor role
secondary factor
Comments

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
National funds
Comments
Environment Agency
Financing type
Local funds
Comments
Whilst the majority of works were financed by the Environment Agency, some of the river restoration works were funded through local partnership funding
Barrier
Barrier type
Attitude of relevant stakeholders
Barrier role
main barrier
Comments
Local councils were initially opposed to the features that they thought would cause loss of their parks and the amenity value, until they saw evidence to say it improved.
Driver
Driver type
Public pressure
Driver role
main driver
Comments
The was a public and political desire to have a flood storage area, to ensure that the trees downstream of Manor Park were safeguarded.
Driver type
Past flooding events
Driver role
main driver
Comments
Flooding events occuring with an existing culverted channel meant that an alternative solution had to be found.
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
Increase Water Storage
Target purpose
Peak-flow reduction
Target purpose
Oher Societal Benefits
Target purpose
Improved Biodiversity
Policy wider plan
Comments
Other plans, such as catchment flood managment plan have been implimented since the NWRM was implimented.
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.
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
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.
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.
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
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.
Soil quality overall soil improvements
N/A info

Partners

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