SRA Annual Report 2018-19: Pioneer dredging – Oath to Burrowbridge (W1)

In July 2017 the Board of the SRA approved dredging the River Parrett between Oath and Burrowbridge, as soon as a legally compliant and affordable scheme could be found. Planning began in late 2017 and continued throughout 2018-19.

The scheme is being led for Somerset Rivers Authority (SRA) by the Parrett Internal Drainage Board (IDB), working closely with the Environment Agency and Natural England. The SRA is using Growth Deal funding from the Heart of the South West Local Enterprise Partnership.

This dredge is particularly important because it would supplement other dredges of the Parrett and Tone since 2014. It would tie in with other projects, such as enhancing the River Sowy (a.k.a. the Parrett Flood Relief Channel) and King’s Sedgemoor Drain. It would help the SRA to reduce flood risks across a large part of the Somerset Levels and Moors that were badly affected in winter 2013- 14 and summer 2012, particularly Aller Moor, King’s Sedgemoor, Moorlinch, Muchelney, Huish Level, Wet Moor, King’s Moor, and Witcombe Bottom. In total, it could potentially reduce flooding to around 65km2 and benefit around 200 homes.

Design, bathymetric and topographic surveys, numerical modelling and the production of environmental surveys and reports have all been undertaken. Design cross-sections have been produced to sensibly maximise the additional flow achievable in the river within physical, environmental and budgetary constraints.

Modelling has shown that works should be focused on a 2.2km (1.4mile) stretch between Beazley’s Spillway at Stathe and the confluence with the River Tone at Burrowbridge where greatest hydraulic impact can be achieved. It is proposed to remove 22,000m3 of sediment using conventional methods with long-reach excavators on banks. Sediment will be used to widen banks and strengthen the Southlake reservoir dam wall.

In some areas, two-stage channels with marginal berms and areas of shallow water will be created. These improvements could benefit water voles, otters, fish, birds and invertebrates. Special attention has been paid to the need to protect hairy click beetles.

Subject to the results of statutory consultations, the SRA hopes to carry out legally- compliant works in autumn 2019.

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