Member News - Atkins Ltd

Atkins restoration strategy for River Wensum


 

Background

The River Wensum, Norfolk, UK, is a chalk river with both national and international conservation interests, as well as being of great recreational value. It is designated as a Site of Special Scientific Interest (SSSI) and Special Area of Conservation (SAC), and is also recognised as a priority chalk stream habitat by the UK Government. The river remains in unfavourable ecological condition due to a number of factors, including in-stream barriers, impoundments and physical modifications such as widening, deepening and straightening of the channel.

Recognising the importance of taking a holistic approach to river restoration and the diverse range of skills reqluired to undertake such a task, the EA employed Atkins; a multi-disciplinary engineering consultancy, as the lead restoration consultant in 2009.

Since then, Atkins has been tasked to further develop and implement the River Wensum Restoration Strategy (RWRS); a high level catchment scale restoration plan, that was originally conceived in 2007 in response to the UK Government's Public Service Agreement (PSA) target to restore favourable condition to SSSIs by 2010. However, the project driver has since been superseded by the requirement to restore the River Wensum to Good Ecological Potential under the EU Water Framework Directive (WFD).

Project Components

Atkins has provided technical support to identify and tackle issues that were working against the aims of the RWRS. The following components were developed to provide incremental longer term improvements to river form and function:

Feasibility & Environmental Scoping Reports

Atkins has produced 10 Feasibility & Environmental Scoping Reports for 71km of river, including nine SSSI Units that comprise the Wensum, and also a substantial length of channel where the Internal Drainage Board (IDB) is the Operating Authority.

The Feasibility Reporst, which include conceptual restoration designs, build on the overarching RWRS and provide sufficient detail to address constraints on the river's SSSI/SAC condition, and satisfy WFD objectives. They have allowed Atkins' proposals to move away from the opportunistic nature of some projects by taking a holistic approach to river restoration. This has enable Atkins to not only address physical modifications within the river, but also to put forward a number of recommendations to align current river management practices with the RWRS.

Each report covered; the environmental baseline; consultation with key stakeholders; selection of restoration measures using Multi-Criteria Analysis; outline restoration designs; construction cost estimates; Environmental Scoping; consent requirements; and identification of project risks.

The level of detail within these reports enables the EA to use them for decisions on consenting, enforcement, and guidance for maintenance and capital works, as well as the selection of restoration projects against their abilitly to deliver an improvement in river condition.

Atkins has found that engaging local stakeholders early in the restoration process not only allows their feedback to be incorporated into the design, but also builds project momentum and support. Therefore, documents are published on the EA's website to allow direct public access (http://www.environment-agency.gov.uk/homeandleisure/wildlife/114676.aspx).

Detailed Restoration Designs & Supervision

Atkins has provided detailed designs, site supervision and construction advice for 8km of river restoration, including 6 major and 3 minor works that have been developed from the Feasibility Report outline designs.

At the detailed design stage, each project has demanded a bespoke approach to account for the river character, stakeholder needs, budgets and aspirations. Designs aim to provide the appropriate density and variation of hydro-morphological features, utilising a variety of restorations measures ranging from conventional bio-engineering, to large woody debris, bed raising, composite gravel glides, re-alignment (above) and excavation. Designs also seek to maximise the use of on-site materials to reduce both the project's costs and carbon footprint.

In 2012 Atkins designed restoration projects on the River Wensum provided the EA with 84% of its national Operational Performance Measure 4c:Works to riverine SSSIs to meet WFD objectives.

Targeted Maintenance Protocol (TaMP)

The Feasibility Report assessment of the flood rist management (FRM) maintenance works showed that only Targeted Maintenance had a positive influence on the river environment. All orther maintenance, including "Continue as present" options had detrimental environmental effects.

To address this, Atkins produced a Targeted Maintenance Protocol that incorporates cost benefit appraisal for the FRM based maintenance works. This enables the results to be used as 'Performance Specifications' for the 5 System Asset Management Plans that cover the River Wensum and will ensure that FRM works comply with the RWRS objectives, within the timescales set under WFD.

The long term net effect of this protocol is substantial, and reduces the burden of environmental improvement falling solely on river restoration projects. Targeted maintenance also provides efficiency savings to the maintenance body (in this case the EA or IDB).

Mills Operating Protocol (MOP)

With 14 mills affecting about two-thirds of the 71km of rhe River Wensum, managing structure operation was seen as a necessary alternative to structure removal, which can be both politically and financially challenging.

Atkins devised a coherent management protocol, aligned with the RWRS, which established a communication chain between the EA and mill operators. This protocol encouraged the consistent operation of mill structures to control whole river flood risk and provide more appropriate habitat.

Monitoring Protocol

With projects envisaged for several years, it was identified that there was a need for consistent and comparable data that could be economically gathered and used to both inform designs and confirm that restoration project objectives were being met.

To this end, Atkins developed an ecological monitoring protocol that has enabled the project team to empirically measure the success of the restoration schemes.

Atkins Ltd are a member of the Water Industry Forum. For more details on Atkins Ltd including contact details, please click here.

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