This page contains a Flash digital edition of a book.
7.5.7.3 Suspended Sediments 176. Measurements of suspended particulate matter (SPM) within the proposed East Anglia THREE site showed concentrations of 3 - 13.5mg/l throughout thewinter of 2012/13.


177. The pattern of SPM in the water column within the proposed East Anglia THREE windfarm area mirrors the governing wave climate, with only a modest modulation due to tidal current speeds alone.


178. Suspended sediment concentrations nearer the coast can be greater and values up to 170mg/l have been recorded in the vicinity of the coast at Great Yarmouth (ABPmer 2012a). This provides a natural background context for the assessment of effects of any temporary increases in suspended sediment concentrations that may arise due to the proposed development.


7.5.7.4 Littoral (Shoreline) Transport Pathways and Coastal Erosion 179. The northern extent of the offshore cable corridor for the proposed East Anglia THREE project is coincident with a promontory in the shoreline at East Lane, Bawdsey. This forms a partial barrier to sediment moving south within the littoral zone from Hollesley Bay further north. The defended promontory at East Lane also exerts an artificial control on the planform evolution of the shore further south.


180. The Bawdsey foreshore consists of London Clay overlain by marine gravel and sand beaches (ABPmer 2012c). The low cliffs are pre-glacial Crag deposits, mainly composed of sand and gravel, and represent a small source of sediment to the coast to the south (ABPmer 2012c). There is a net southerly transport of sediment along the shore, but cross-shore transport from the shore to the nearshore zone is also important (Royal Haskoning 2010).


181. There is a large, nearshore, shingle bank system which forms the ebb-tide delta at the mouth of the River Deben estuary. This system is called The Knolls and is a function of the longshore sediment supply from the north which interacts with the flow in and out of the estuary. Periodically, there are changes in the position and form of the banks, driven by storm waves (Burningham and French 2006).


182. The Knolls are important features in forming a large, temporary, sink for sediment (which at other times can also be a source of sediment to frontages south of the estuary, depending on the prevailing conditions). The banks also act to modify wave action (reduce wave heights and alter wave transformation processes to shore) and in doing so influence sediment transport at the mouth of the estuary (HR Wallingford et al. 2002).


Preliminary Environmental Information May 2014


East Anglia THREE Offshore Windfarm Chapter 7 Marine Geology, Oceanography and Physical Processes Page 37


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