frequency-dependent absorption (Thorpe 1967), surface scattering (Coates 1988; Medwin and Clay 1998; Ainslie et al. 1994) and sea bed properties (Hamilton 1980; Lurton 2003). The modelling methodology is described in more detail in Appendix 9.1.
21.
The modelling has been completed at 20 single pile locations inside and around the boundary of the East Anglia THREE site to represent the geographical extent of the windfarm and to account for bathymetric features so as to suitably capture the variability in the regional underwater sound propagation.
22.
The effect of receptor position in the water column has been considered and is discussed further in Appendix 9.1. Appendix 9.1 presents the predicted impact ranges expected around mid-water column for marine mammals, and mid-water and also close to the sea bed for fish, where levels are expected to be lower. It should be noted that substantial variation is expected throughout the water column and animals closer to the surface would be exposed to lower levels than those predicted around mid-water column. This is illustrated in depth dependent modelling outputs shown in Diagram9.3 and Diagram 9.4 for a north and south transect of an example location in the East Anglia THREE site, respectively.
23.
Full details of the underwater noise modelling and the results of this are provided in Appendix 9.1. An example noise propagation map is shown in Diagram 9.1.
Preliminary Environmental Information May 2014
East Anglia THREE Offshore Windfarm
Chapter 9 Underwater Noise Page 6
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