Rivers Authority Board Paper

Title: SRA Enhanced Programme - Work Items 2017/18

RECOMMENDATION

The SRA Board is asked to:

 Note the work that has been carried out so far to promote works in the Brue catchment.  Recognise the environmental constraints, and the regulatory and financial challenges that exist to promoting this work.  Note the lack of consensus on reduced flooding that can be achieved  Note the intention to develop the model (previously approved)  Approve the proposal for a “Brue Plan” workshop early in 2018 to

investigate the potential for more holistic and proactive approach to managing flooding in the Brue Catchment.

Purpose

To update the Board on the difficulties in delivering planned work in the Brue catchment and propose a new way forward. This paper elaborates on these difficulties and proposes a proactive approach to; identifying where the need to reduce flooding from the River Brue and its tributaries exists, recognising the environmental constraints and opportunities, and delivering good value for money.

Background and context

Funding has been available in the SRA Enhanced Programme and LEP funding for 3 items of work on the River Brue since 2015/16.

 Brue Banks, 2016/17  Brue Desilting 2015/16  Brue Trees. 2015/16

Although there were initial delays as a result of recruiting and retaining staff difficulties, once these were resolved all partners have expended considerable time and effort in investigation, survey and preparatory documents to develop these projects to delivery. Despite this investment, no work has been delivered on the ground.

The principal reasons are

 Challenges around achieving legally compliant schemes as a result of o No consensus that the work will deliver adequate reduction in flooding

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o Concerns over the direct environmental impact at the locations of the works o Concern over the indirect environmental impact of the work across the wider floodplain.  Cost

Latest Status

Brue Banks.

This scheme was proposed to reduce the risk of flooding by restoring raised banks that are in poor condition due to settlement, erosion and burrowing animals. These improvements would also enable safe access for machinery to undertake watercourse maintenance thereby ensuring the channels ability to convey flood flows more effectively within the raised banks.

The initial sum in the budget of £50k was insufficient to provide a design including an Environmental Impact Assessment. An outline cost estimate for delivering work on the ground was estimated by the at 1 million pounds per kilometre. On this basis a paper was submitted to the Board that the project was not economically sustainable given the flood risk to limited numbers of properties.

The Board agreed to withdraw the balance of £40k from developing the project further and asked for further paper outlining alternatives to be brought to them.

Brue Desilting

River Brue desilting is being promoted through the SRA’s dredging strategy. An initial length between and North Drain Pumping Station was selected to be desilted as there are considerable soft silt deposits on the bed of the channel. These reduce the cross section area, raise bed levels and encourage more vigorous growth of aquatic vegetation. All of which can reduce the ability of the channel to convey flood flows. This increases the likelihood of over spilling the raised flood banks into the adjacent low lying areas where flood water has to be pumped back into the River Brue when river levels have receded.

However it has not been possible to achieve consensus between the partner organisations that desilting of the River Brue will achieve a meaningful reduction in flood risk.

Hydraulic modelling using the Environment Agency River Brue Model was proposed to investigate this further but the model requires development to be used for this purpose.

Early discussions with the Environment Agency and Natural raised concerns regarding the direct environmental impact of the work in channel and the indirect

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environmental impact of reduced frequency of flooding to adjacent areas where environmental designations exist. .

Brue Trees

This action is to develop and implement a programme of tree management in the lower reaches of the River Brue to improve conveyance of flood flows and reduce the frequency and severity of flooding in areas which flood upstream. However it has not been possible to reach a consensus between partner organisations that this work will achieve a meaningful reduction in flooding. It was therefore proposed that the EA model should be used to predict the likely impact of this proposal.

The EA River Brue Model was provided to the IDB in December 2016. Since then a review of the model undertaken by the IDB concluded that the model is not suitable in its current form. The EA and their consultants were informed and some modifications were implemented but further development of the model is needed.

A hydraulic assessment and mapping exercise was carried out using a “cut down” version of the model to evaluate the relative flood benefits that can be achieved from channel conveyance improvements in the lower River Brue.

An Environmental Impact Assessment (EIA) Scoping Assessment, Water Framework Directive (WFD) Scoping Assessment and Regulations Assessment (HRA) Scoping Study were submitted to the Environment Agency and .

Following a site visit with the Environment Agency and Natural England in November 2017, concerns were raised over potential loss of and insufficient hydraulic justification for the proposal. Consultation is ongoing with the Environment Agency to clarify any additional assessments and refinements to the approach that may be required for these works to be considered compliant with environmental legislation.

The proposed works have therefore been delayed

Summary

Considerable effort has been expended to promote actions aimed at reducing flooding from the River Brue. However across all “Brue” projects a lack of consensus over the extent and impacts of reduced flooding that can be achieved along with environmental concerns and in some cases costs have caused none of these projects to proceed to delivery.

In these circumstances it must be considered whether or not it will be possible to deliver any flood reduction measures under work stream W1 (Dredging and River Management) in the Brue Catchment without a more holistic proactive approach to catchment function and sensitivities. ITEM 9 Brue Paper December 17v3 .Docx 3

Proposal

Continued efforts should be made to reduce damaging floods within the Brue Catchment. However to ensure that all SRA partners are supportive of future actions before they are promoted through SRA delivery programme(s) a more holistic proactive approach at a catchment scale should be taken to identify flooding issues, opportunities and sensitivities. A workshop with partners is therefore proposed early in 2018 to explore the potential for successful outcomes and start to develop an agreed approach.

A key tool that will be necessary to inform decision making will be the Brue Hydraulic Model and it is further recommended that the EA and the IDB should work together to develop the model to be suitable for this purpose.

Recommendation

 Note the work that has been carried out so far to promote works in the Brue catchment.  Recognise the environmental constraints, and the regulatory and financial challenges that exist to promoting this work.  Note the lack of consensus on reduced flooding that can be achieved  Note the intention to develop the Brue model (previously approved)  Approve the proposal for a “Brue Plan” workshop early in 2018 to investigate the potential for more holistic and proactive approach to managing flooding in the Brue Catchment.

Author: Iain Sturdy (Somerset Drainage Boards Consortium)

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