Not a Bore Issues of Tidal Power in the Severn Estuary

1. Not a Bore? Issues of Tidal Power in the Severn Estuary Agenda University of the West of England 30th June 2008

3. Severn Tidal Power ‘Not a Bore?’Engineering factors and technologies Dr Mervyn Bramley Visiting research fellow

4. Technologies – Tidal range and tidal stream

5. Potential tidal energy capture From tidal range: Power ˜ k1 A H2 H = level difference across barrage / lagoon A = wetted surface area upstream of empoundment From tidal stream: Power ˜ k2V3 V = mean free-stream tidal current

6. Tidal stream array Prototype stage moving to full-scale demonstration Small commercial array up to 5 MW Large array up to 30MW Potential interference with shipping lanes

7. Tidal lagoon – Swansea Impoundment by 9 km length embankment Plan area of 5km2 Mean spring tidal range ˜ 8.5 m Installed capacity 50MW Annual energy output 124 GWh Cardiff Weston barrage ˜ 135 tidal lagoons Estimated cost ˜ £250m

8. Tidal barrage options – different sites Cardiff – Weston Barrage Location: Lavernock Point to Brean Down Length: 16 km (10 miles) Generating capacity: 8.6 GW or 8,600 MW Annual average output: 17 TWh or 17,000 GWh Percentage of UK electricity supply: 4.4% Estimated cost ˜ £15bn

9. Cardiff – Weston barrage A mega engineering project Concrete caissons towed to prepared foundations for sluiceways and turbines Some embankment Shipping lock Connection to national grid Rail or road possibly, but adds considerably to width 200,000 person years of employment – Site works

10. Issues for consideration Are the technologies sufficiently proven and appropriate to be applied at a significant scale in the Severn Estuary? Can the environmental impact of a Severn tidal scheme both during and after construction be adequately mitigated? Can the other uses of the Severn Estuary, in particular ports, commerce and shipping, be accommodated? Could the UK finance and handle a project of the size of the larger Severn barrage proposals? Can the carbon embedded in a Severn tidal scheme be adequately offset by the low-carbon power it generates ? Can we envision a multi-functional scheme and a managed changing environment, or is this our philosopher’s stone?

11. ‘Not a Bore?’A Barrage of Legislation thomas.appleby@uwe.ac.uk Law Lecturer

12. Law views it as land covered by water Needs consent of the owners of the seabed Otherwise compulsory purchase requirements Crown Estate Hanbury Tenyson Family Berkeley Family – Lord Marcher Anyone know where this is? Prize Lot of land covered by water Crown Estate Hanbury Tenyson Family Berkeley Family – Lord Marcher Anyone know where this is? Prize Lot of land covered by water

13. Rights in the estuary Public right to navigate Public right to fish Private fishing rights Private drainage rights Ownership of seabed Public rights of Fishing Public right of navigation Licensed mineral extraction licences Private fishing rights – rivers fixed engines Private rights of drainage Ownership of seabed Public rights of Fishing Public right of navigation Licensed mineral extraction licences Private fishing rights – rivers fixed engines Private rights of drainage

14. The effect of human rights Compensation for interference with those rights Difficult to assess at this stage CompensationCompensation

15. Environmental legislation Habitats Directive Severn candidate ‘Special Area of Conservation’ Requirement to form compensatory habitat for protected features lost to power scheme Special Area of Conservation Compensatory requirements under the Habitats Directive for lost habitat Compensatory Habitat required for area disturbed Special Area of Conservation Compensatory requirements under the Habitats Directive for lost habitat

16. Not that difficult? Capital engineering costs plus Compensation costs for people’s rights Compensation for the environment Cost New Act of ParliamentsCost New Act of Parliaments

17. Severn Barrage ‘Not a Bore?’ Sediment Distribution and Flood Risk Sue Marriott and Chris Spencer

18. Current issues Sediment What types of sediments exist in the estuary and how are they distributed? Where does the sediment come from? Is the sediment contaminated? Flood risk

20. Sediments How will the barrage impact on sediments? Circulation by tidal currents restricted to Bristol Channel below barrage Fine sediment can settle in lagoon behind barrage making water clearer, allowing ultraviolet penetration therefore cleaner water plus photosynthesis and phytoplankton blooms Contaminated sediment from floodplains may build up Build up of sediment may reduce volume of upper estuary

21. Flooding Flooding What contributes to flood risk in the area? What will the effects of the barrage be? Lagoon will raise water tables so river water may not drain away so quickly May cause extra deposition of mud in lower reaches of rivers due to lower gradients reducing capacity Increased flood risk in lower reaches and backing upstream

22. Increased flood risk upstream?

23. Future Sea-Level Rise Sea-level rise will have impacts on coastal areas due to increased erosion and increased flood risk Would also cause backing up of river water in lower reaches Barrage may be opened during high river flows to move water out quicker Erosion energy will be reduced behind barrage Could a barrage help mitigate against future sea-level rise?

24. Issues for consideration Would a barrage result in changes to sediment distribution? Will changes have impacts in the Bristol Channel? What are the implications of raised water tables in the surrounding areas? What is the likelihood of an increase in contamination of estuarine sediment? What are the likely impacts on sediment and flood risk of other tidal power generation options? Costs of extra coastal and flood defences needed due to future sea-level rise vs cost of barrage?

25. Severn Barrage ‘Not a Bore?’The Estuarine Ecosystem david.bird@uwe.ac.uk Environmental Biologist

27. Estuaries support huge numbers of invertebrates – but few species

28. Estuaries support huge numbers of invertebrates – but few species

29. 100+ fish species have been recorded from the Severn Estuary & Bristol Channel

32. Issues for consideration:

33. Questions for the BERR Feasibility Study to Address The following slides provide a list of questions for the BERR Feasibility Study to address as formulated by the participants at the Not a Bore Science Café Event. Some 85 people drawn from the Bristol hinterland attended the Science Café event held at the University of the West of England on 30th June 2008. Following a series of short scene setting presentations participants discussed the implications of tidal power from the Severn estuary. Arising from these discussions are a list of questions that the BERR Feasibility Study should address.

34. Questions for the BERR Feasibility Study to Address Will the evaluation make comparison with the potential impact and input of other low carbon energies such as wind and solar? Will the SEA evaluate the human costs in the areas following changes arising from an energy capture system in the Severn? Given that environmental impact is a necessary consequence of whatever system is put in place, rather than compromise why not go for the project that produces the most power and maximises the low carbon energy potential? Will the SEA evaluate such a scenario? Why is tidal power from the Severn back on the political agenda? Will the SEA and Feasibility Study consider implications for Human Rights? How will the proposed schemes affect local communities? How will a tidal power scheme benefit the South West? Will the preferred scheme be evaluated against other forms of renewable energy? Is consideration being given to smaller community based energy schemes? How will the Feasibility Study ensure that the selected tidal power scheme will not be a white elephant?

35. Questions for the BERR Feasibility Study to Address How confident can we be that the Feasibility Study methodology is not biased in favour of any particular type of technology or size of scheme and that it takes account of the cost effectiveness of non-tidal power alternatives to put the study’s conclusions in context? What are the likely health impacts of a barrage particularly in construction and also through increased risk of flooding. How are the cultural aspects/damage/change to be costed? The Severn bore is a unique natural phenomenon – how can a monetary values be put on it? If a barrage is the preferred option how will sufficient aggregate be sourced to build the structure? Will the Feasibility Study identify the responsible parties to undertake environmental compensation? What will be the impact of any scheme on flood risks?  Will the flood scenarios considered actually be worst case? How will the commercial effect on the Bristol's Docks be taken into account?

36. Questions for the BERR Feasibility Study to Address How is the lack of scientific and engineering knowledge being addressed?  Will ownership of a scheme be considered in the feasibility study?  How certain are the cost estimates? Are allowances made for the legal compensation that will be required? How seriously are the alternatives to a barrage being considered? How much energy conservation could the likely cost of a Weston – Lavernock Barrage buy?  What is the payback period for the carbon footprint? What will be the impacts on the ecology and how certain can we be that the ecological compensation schemes will be able to replace the lost biodiversity? How confident are we that a tidal power scheme will be future proof? Will a scheme be as efficient in 10 years time as the day it is commissioned? What effect will the discontinuous operation of a tidal power scheme have on the supply of electricity and on the maintenance of the site?