Design of an environmentally aligned flood alleviation scheme: the Burn of Mosset, Moray, Scotland

• 14.1.

  Introduction

• 14.2.

  Background

• 14.3.

  Option development and appraisal

• 14.4.

  Preferred option

• 14.5.

  Implementation

• 14.6.

  Post-project performance and appraisal

• 14.7.

  Knowledge transfer and lessons learned

• Acknowledgements

• References

• Further reading

Forres, Scotland, has a long history of flooding from the Burn of Mosset, and it was forecast that, without investment in flood risk management, flood damages were likely to exceed £43 million over the next 50 years. The decision was taken to implement a flood alleviation scheme (FAS) featuring an earth-fill dam upstream of Forres, capable of storing up to 3.8 million m³ of water and limiting peak discharges into the urban area to 8.5 m³/s. It was recognised that sediment- and debris-related risks to the performance of the structure had to be managed and Burn Management Works were designed using cutting-edge river restoration techniques for channel rehabilitation and habitat creation to enhance the capacity of the flood basin to store sediment and debris. The FAS was opened on 28 August 2009 and the dam impounded flood water for the first time on 4 September 2009, avoiding approximately £9 million of flood damages to the town of Forres. The Burn Management Works have evolved mostly as expected, although some features have not functioned as intended, and lessons have been learnt concerning the need to allow for unexpected developments when using ‘prompted recovery’ in flood risk management and river rehabilitation.