Assessment of the Significance of Changes to the Inshore Wave Regime as a consequence of an Offshore Wind Array

Abstract:

This document is the final report for the project titled 'Assessment of the Significance of Changes to the Inshore Wave Regime as a consequence of an Offshore Wind Array'.

Offshore windfarm (OWF) development within the UK is presently in the Second Round of licensing by Defra through FEPA (1985). Many of the Round One licences have already been granted, and of these, the development on Scroby Sands was one of the first. More significantly, Scroby Sands is amongst the few OWFs situated in a dynamic sedimentary environment. It is also close to a coastline which is vulnerable to erosion and which has seen numerous different coastal protection schemes in recent years. Development of the OWF at this site was started in autumn 2003, and electricity production commenced in December 2004.

This report details work undertaken only under contract AE1227. It was anticipated that this work would provide evidence-based research from which to refine any requirements for monitoring of waves that have been included within licence conditions of Round One developments, and that could be included within those conditions for Round Two developments.

The sensitivity analysis enabled by the modelling showed that for a simplistic flat seabed, wave interference patterns were most pronounced for waves approaching the monopile array obliquely, at an angle of 35 degrees. For more realistic bathymetry, this angle was decreased, but more significant was the maximum reduction in wave height from 5% (flat seabed) to 2% (realistic bathymetry). Thus, effects of wave refraction in shallow water are greater than those of monopile-related wave diffraction and interference. Wave refraction in shallow water acts to reduce any effect of the monopiles upon waves.

The quantitative value of predicted change to wave height as a result of monopile arrays, of 2%, is in agreement with those estimates presented as part of the Environmental Statements for other more recent windfarms. It has not been possible to detect this small change using the presently available measurement and analysis techniques afforded by X-band radar. It is therefore concluded that wave diffraction and interference effects arising from monopile arrays are negligible. By inference, any effect on coastal erosion is therefore also likely to be negligible.

1. Scientific Objectives
2. Summary of Success (Against Scientific Objectives)
3. Methods
4. Results
5. Discussion
6. Conclusion
7. Implications & Significance
8. Future Research
9. Resulting Actions
10. References

Publication Year:

2005

Publisher:

Department for Environment, Food & Rural Affairs

DOI:

No DOI minted

Author(s):

CEFAS