41.


Consequently, the scour development may vary across the East Anglia THREE site from the predictions made at modelling point 3, depending on the precise water depths considered (and of course the associated foundation size ranges, metocean conditions and sediment properties at those water depths).


42.


In order to test the sensitivity of the scour predictions made at modelling point 3 to the influence of increased water depth, further consideration has been given in a comparative test in 45m depth of water. The conical gravity base structures have been considered as the ‘worst case’ in these tests, with a basal diameter of 55m; this being the upper structural dimension for water depths in the range of 35 to 45m.


43.


The increases in wave height under different extreme return period events due to progression further offshore across the East Anglia THREE site into deeper water from modelling point 3 have been estimated by inspection based on the full suite of results from the seven modelling points across the East Anglia Zone.


44.


The increases in current speeds under different extreme return period events that are associated with a greater depth of water have been estimated as an average of the full suite of results from the seven modelling points (shown in Appendix 7.2 Figure 7.2.2).


45.


The results presented in Table 7.6 show that despite the increase in basal diameter of the gravity base structure, there would also be a reduction in wave-induced stirring at the sea bed due to increased water depth. Consequently, the depth of the scour hole is predicted to be less and, in turn, the scour volume would be smaller than that previously considered at modelling point 3.


Table 7.6 Comparative Test of Scour Hole Development Location


Water Depth (m)


Modelling Point 3


East Anglia THREE


‘deeper water’ test 30.8


Basal Diameter


(m) 50


50 1


45.0 55 50 7.5 12.6 1.54 5,549 868


Return Period (years)


1


Wave Height Hs(m)


6.1 7.3 6.3


Wave Period Tp(m)


11.1 12.3 11.5


Current Uc(m)


1.30 1.40 1.38


Scour Area (m2)


4,775 5,963 5,312


Scour Volume V(m3)


1,003 4,580 481


Preliminary Environmental Information May 2014


East Anglia THREE Offshore Windfarm Chapter 7 Marine Geology, Oceanography and Physical Processes Page 11


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76  |  Page 77  |  Page 78  |  Page 79  |  Page 80  |  Page 81  |  Page 82  |  Page 83  |  Page 84  |  Page 85  |  Page 86  |  Page 87  |  Page 88  |  Page 89  |  Page 90  |  Page 91  |  Page 92  |  Page 93  |  Page 94  |  Page 95