Storms Desmond and Eva in late December 2015 led to record river levels in many river catchments, 453 properties and 174 businesses flooded in York. The Environment Agency and City of York Council were successful in attracting funding to renew existing and provide new flood defences. The York Five Year Plan was developed and detailed business cases and designs for schemes in 19 flood cells across the city have been delivered. An adaptive approach to flood resilience has been developed, work programmes to develop increased flood storage and the incentivised delivery of natural flood risk management measures have commenced.
The challenge
The city of York is located in the Vale of York on the confluence of the rivers Ouse and Foss. Centred on this urban core, the administrative area extends to include villages of varying sizes and largely rural land with the River Derwent forming the eastern boundary. The Rivers Swale, Ure and Nidd combine upstream of York to form the River Ouse, a 3000km2 river catchment drains through the Ouse with almost 600 tonnes of water a second flowing through the city centre in significant flood events.
We have experienced a wide range of flood events from our rivers in York - major flooding in 1982, 2000 and 2015. The main river level gauge in the city has one of the longest continual records in the country and peak annual maximum levels show a steady rise in river levels in our city with the vast majority of major events occurring in the last 30 years.
Flood defences built in the late 1980’s and early 1990’s protect the vast majority of communities from flooding on the River Ouse and Foss and their tributaries, but their standard of protection has declined over this period and communities are facing a greater level of risk than before.
However, the walls and embankments in York cannot continue to be raised inconsequentially into the future, the impact on the way in which the city lives alongside its rivers would be irreparably damaged and would not be readily accepted.
The solution
City of York Council and the Environment Agency were aware of the need to improve the cities flood resilience following a number of significant flood events, notably two events in 2012, where our defences performed effectively but river levels were beginning to test the defence levels.
The Boxing Day floods of 2015 were the highest floods on record on the River Foss and the equal second highest on the River Ouse. The flooding followed an intense period of rainfall across November and December due to the impacts of Storms Desmond and Eva. More than 4,000 homes and 2,000 businesses flooded across Yorkshire with 453 properties and 174 businesses flooded in York.
Working in partnership the Environment Agency and City of York Council were successful in attracting funding, funding was allocated to the Environment Agency following the floods to renew existing and provide new flood defences across the city, £38m has been allocated to the Foss Barrier improvements and a total of £64m to the wider flood defences across the City of York.
The York Five Year Plan was developed and detailed business cases and designs for schemes in 19 flood cells across the city have been delivered, and works are complete in all but two locations.
Our city will always rely on some degree of direct and localised physical flood protection, our walls, embankments and pumping stations are essential to manage the scale of river flow during significant flood events. However, an adaptive approach to flood resilience has been developed to ensure these physical interventions still allow the city’s residents, businesses and visitors to safely enjoy our riverside areas. Defence hights have been capped and in some locations glass panels have been incorporated and locations and sizes of floodgates have been carefully considered to allow an unimpeded view of the cities key landmarks when defences are not in operation.
The current defence improvements incorporate levels that manage climate change impacts through to 2039. After this date the defences will continue to provide a level of protection, but this will degrade as future climate change scenarios lead to more rainfall and a resultant increase on river flows through the Rivers Swale, Ure and Nidd and ultimately into the River Ouse as it flows through city.
A programme of catchment scale interventions will be needed to provide this future adaptive climate change resilience.
Catchment scale modelling has commenced. It is envisioned that this will evidence a combination of flood storage and natural flood management measures such as afforestation, upland management, works to river margins and changes to farming practices which will provide a reduction in peak runoff downstream leading to reduced flood risk not just in York but in many other urban settlements in the catchment.
City of York Council have been successful in the award of £6m of Defra funding through the Flood and Coastal Resilience Innovation Programme to develop this work further.
The impact
The York Five Year Plan has developed, at significant pace, improvements to existing defences in the city giving an increased flood protection into the future. Appraisal, design and delivery has been developed in tandem across a number of projects by a multidisciplinary team allowing a range of efficiencies, savings and best practice to be developed.
How is the approach being sustained?
The final construction phases of the York Five Year Plan will complete over the next two years, the schemes assets will continue to be maintained and operated by the Environment Agency, City of York Council and Yorkshire Water. Extensive emergency planning and response plans ensure smooth operation of the defences. Regular review, exercising and investigations ensure the defence measures continue to be fit for purpose for the city.
The need for continued catchment scale interventions is recognised by all key partners, the existing innovation funding will be used to develop the approaches through to 2027, where possible the project will also inform catchment storage needs alongside Environment Agency led work.
A devolved North Yorkshire will be set up during this time with significant aspirations to develop blue/green infrastructure and climate resilience this along with the mature catchment partnerships and a desire to work strategically across administrative boundaries will support a holistic catchment wide approach to climate resilience.
A permanent strategic approach to whole catchment management of flood risk and climate resilience needs will be sought through this work to support the development of long-term funding and delivery strategies.
Lessons learned
Despite ongoing works, the York Five Year Plan has already achieved its major target to better protect 2000 homes and businesses in York. A range of review and lessons learnt workshops were carried out to recognise this and develop a set of recommendations that could be shared with the wider flood risk community and the framework providers that have developed the scheme.
Although resource intensive, the approach of developing a range of flood cells across an urban area in tandem was seen to have delivered significant gains in terms of co-development, shared goals and partnership working. Many aspects of scheme appraisal, design and delivery presented difficult problems with often complex solutions, but all partners were able to work together to overcome these.
The agreed approach to adaptive resilience is indicative of a forward-thinking partnership and will hopefully help in the development of a sustainable and effective strategic level delivery model as the innovation project commences. The sheer size of the innovation work will deliver many areas of learning, but it is too soon to reflect on these at present.