331. In addition, previous wave modelling of the effect of the proposed East Anglia ONE project on the wave regime has been used as an analogue for delineating the ‘zone of potential influence’. In that previous modelling assessment, the greatest change along the above-defined axis of greatest potential influence arose under a 1 in 10 year wave condition. The spatial extent of measureable changes (≥ ±5% of the baseline conditions) under such an event was mapped and superimposed over the East Anglia THREE site. The resulting ‘zone of influence’ on the wave regime is presented in Figure 7.7. Whilst it is recognised that there are differences in metocean conditions, water depths and likely gravity base sizes between the two project sites, it is believed that the highly conservative nature of the previous numerical modelling (including considerably greater number of foundations) more than covers any differences in effect that may arise due to these factors.
332. The identified receptor groups for marine geology, oceanography and physical processes are remote from the zone of influence. Due to this, no pathway exists between the source and the receptor, so in terms of impacts on these receptor groups there is no impact associated with the proposed project.
7.6.2.3 Impact 3: Changes to the sediment transport regime due to the presence of foundation structures
333. Modifications to the tidal regime and/or the wave regime due to the presence of the foundation structures during the operational phase may affect the sediment regime.
334. The issue of local scour around the foundations is considered separately (see operation impact 4, section 7.6.2.4) whilst this section addresses broader patterns of suspended and bedload sediment transport across, and beyond, the East Anglia THREE site and littoral sediment transport at the shoreline.
7.6.2.3.1 Assessment of effect magnitude and/or impact significance 335. The reductions in tidal flow (operation impact 1) and wave height (operation impact 2) that are anticipated to be associated with the presence of the largest foundation structures (Table 7.3 and Table 7.7) during the operational phase would result in a reduction in the sediment transport potential across the areas where such changes are observed. Conversely, the areas of increased tidal flow around each wind turbine would result in increased sediment transport potential (and in doing so generate local scour – see Impact 4).
336. These changes to the physical processes would, however, be both low in magnitude and largely confined to local wake or wave shadow effects attributable to individual wind turbine foundations and, therefore, would be small in geographical extent. In the case of wave effects, there would also be reductions due to a shadow effect
Preliminary Environmental Information May 2014
East Anglia THREE Offshore Windfarm Chapter 7 Marine Geology, Oceanography and Physical Processes Page 66
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