Nottingham Trent Left Bank Flood Alleviation Scheme

Nottingham Trent Left Bank Flood Alleviation Scheme
We have listed below a number of frequently asked questions (FAQs) raised by consultees who responded to the Nottingham Trent Left Bank Flood Alleviation Scheme Scoping Report (November 2017).

Why are we not looking at floodwater storage areas rather than physical defences?

The Scoping Report (Section 4, pages 33-36) describes the appraisal process we have followed to arrive at the conclusion that flood defences are the most suitable option for reducing flood risk to Nottingham.

The Fluvial Trent Strategy, published in March 2004, considered 18 generic flood risk options along the 200km of the Trent, including Nottingham. The Strategy concluded that storage is not suitable as a stand-alone solution to reducing flood risk to Nottingham because high flows are experienced for long periods of time when the Trent is in flood. The Strategy specifically considered a large flood storage reservoir upstream of Nottingham as a possible option. The proposal was for a dam across the floodplain adjacent to Weston-on-Trent to store flood waters upstream. During a flood event, this reservoir would reduce the flow of the Trent through to Nottingham by 50%.

However the option was not taken forward for detailed consideration for the following reasons:

There was not enough available space within the Trent Valley to store the large volume of floodwater in a way that was environmentally acceptable.

The upstream storage would inundate the villages of Barrow and Swarkestone. The complete relocation of these villages would be required.

The solution would not provide complete protection to Nottingham . The proposed storage area is upstream of the Rivers Derwent and Soar and it therefore does not solve the potential problem of Nottingham flooding from these rivers. Therefore, new flood defences, albeit at a reduced height, would still need to be constructed through the city.

 

What are the effects of the Nottingham Left and Right Bank schemes on the outlying areas and villages in the Trent floodplain? What is being proposed to look at these effects?

During the computer modelling for the scheme it became clear that the proposed raising and reconstruction of defences would have an adverse effect on water levels in areas surrounding Nottingham during extreme flood events. The scheme computer model predicted that in the worst case a rise in the 100-year flood level of 0.06m may be experienced in some areas. The Scoping Report (Section 6, page 59 – 60) identified this as an impact of the scheme.

In order to manage this impact we have prepared a ‘Trent Villages Action Plan’ to identify ways in which the adverse effects of the Nottingham schemes on villages in the Trent Floodplain can be reduced. A separate project team has been set up to deal specifically with the affected areas and to assess the viability of a range of flood risk management options for these areas. This project team is based in our Nottingham Trentside office and will operate within the lifespan of the Nottingham scheme.

The work that this project team is undertaking is identifying that real opportunities exist for a wider reduction in flood risk to villages within the Trent Floodplain.

For further information on the work being undertaken by this project team, please contact:

Dave Bartram
Trent Villages Project Manager
Environment Agency Trentside Offices
Scarrington Road, West Bridgford
Nottingham , NG2 5FA

 

Why does the Nottingham Left Bank scheme not extend to cover these outlying villages?

Under the rules set out by the Department for Environment, Food and Rural Affairs (Defra), funding is available for schemes proposed in discrete ‘flood cells’. A flood cell is an area of land that will flood when a breach in defences occurs. We have established that if the Trent ‘s floodwater breached the defences at Sawley, properties on the left bank through Nottingham would be inundated as far downstream as Colwick. The 27km stretch of the Trent ‘s left bank between Sawley and Colwick is therefore a single flood cell. Similarly, Wilford and West Bridgford on the right bank, a distance of 9km, is also a single flood cell. We have therefore sought funding for the left and right bank Nottingham schemes separately.

The areas surrounding Nottingham, including villages downstream of Nottingham lie in separate flood cells. Therefore, we are not able to seek funding to undertake work in these areas as part of the Nottingham Left or Right Bank schemes.

A scheme, or series of schemes, to protect the outlying villages of Nottingham needs to have a viable business case in its own right. A viable business case requires the benefits of providing the scheme to that area needs to weigh up favourably against the costs of providing the scheme.

In order to assess the viability of these schemes, a separate project team as described above has been set up. This team will carry out an appraisal of these areas around Nottingham.

 

Why are the tributaries that flow into the Trent in Nottingham not being included in this scheme? What is the interaction between the Trent and these tributaries?

Section 6.13 (pages 60 and 61) of the Scoping Report describe the Trent ‘s interaction with its tributaries.

The majority of the tributaries flowing into the Trent through Nottingham are small watercourses with a highly urban catchment. These are fast responding and therefore during heavy rainfall, their peak levels have passed before the surge of the Trent arrives, some 24hours later. Our scheme for the Trent , is not going to affect the flood risk along the tributaries. The exception is the Erewash, where we plan to construct some new defences to prevent against the Trent backing up the Erewash and using this as a route for flooding.

As discussed above, Defra requirements state that funding is only available for individual flood cells. For work to be carried out along any of the Trent ‘s tributaries, a separate business case proving the viability of such works is needed.

We do intend to undertake an appraisal into the flood risk along the River Erewash and River Leen. However, this work is not due to be completed until 2007 at the earliest.

 

What are the proposed defences going to look like? Will it affect the existing character of the area?

We appreciate that the defences run through many areas of great landscape character, especially the villages of Sawley, Attenborough, and along Victoria Embankment at Meadows. Private landowners have understandable concern over what the defence will look like through their land, as do the general public where the defences run through parks and gardens. We are employing landscape architects who, in consultation with organisations and interested individuals, will advise on the design of the defence so it will be sympathetic to the existing character of the area. Visualisations of how the defences will look will be included in the Environmental Statement. We will also prepare landscape plans for all scheme areas.

 

I am a private landowner and the proposed flood defences go through my land. When will I get a chance to discuss the scheme in detail?

In the next few months we will be directly contacting all owners and tenants of land which will be crossed by the defences. This will be the start of a consultation process that will continue as the scheme design develops. You will be able to comment in detail on the proposals and ask any questions about how the scheme may affect you. We will also use your comments to help to ensure, wherever possible, impacts are minimised.

 

Will the proposed flood defences affect ground water? What measures will be put in place to combat floodwater rising through drains?

Over the course of the coming months, we intend to undertake computer modelling of the groundwater to confirm the permanent impacts of our flood defences. To calibrate these models and assist in the engineering design, we have recently installed data loggers groundwater level monitors in boreholes to monitor groundwater flow. Our current judgment is that the proposed flood defences will have a negligible impact on ground water. However, this issue will need further detailed analysis and design over the coming months.

A steel flap is typically installed to prevent floodwater rising through drains and discussions are ongoing with Severn Trent Water and the local authorities on an agreeable solution to prevent against the drains ‘backing up’.

 

How are you going to choose the exact alignment of the defence?

The Scoping Report presented several alignment options at each scheme location. The exact line of the defence will be chosen through an iterative process of engineering and environmental considerations. Wherever possible, we will take the views of landowners, organisations and individuals into account. During spring/summer 2006 we will undertake a number of further technical, ecological and landscape surveys to inform this decision making process. We will present our preferred alignment in a consultation document in July 2006. At this time you will have the opportunity to provide further comment.

 

There is real potential to enhance the environment of the River Trent Corridor as part of this scheme, what are you proposing to do?

Many of our consultees highlighted potential enhancement opportunities, in particular for recreation and biodiversity. We will consider all suggestions and where possible incorporate them into our scheme. The scheme we are proposing includes the improvement of local footpaths and recreation areas to create a better quality of life for the people of Nottingham . We are also considering ways in which we can create an enhanced environment for wildlife. These are core components of the Environment Agency’s Vision to ‘Create a Better Place ‘. These opportunities will be described in more detail in the Environmental Statement.

 

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