14 
NORA results: 
The tidal stream vectors for spring conditions indicate how the tidal streams change and decrease with 
increasing distance from the Orkney Islands (Fig. 5). Mean maximum spring speeds near the surface 
decrease from 65 cm/s at 24 m depth at position N1 to 17 cm/s at 15 m depth at position N7 of the NORA 
section (Fig. 6). The corresponding mean maximum neap velocities, which are mostly about half as great as 
the maximum spring ones, decrease from 27 cm/s in the west to about 13 cm/s in the east. The vertical dis 
tribution of spring and neap velocities along the NORA section indicates that the strength of the tidal stream 
is almost vertically homogeneous throughout the whole of the water column. The stream is weakened by 
bottom friction only near the seabed. 
K N1 N2 N3 N4 N5 N6 N7 N8 K 
Fig. 5 Spring tidal stream figures in the NORA section, representing speed and direction (north up) from 6 hours be 
fore until 6 hours after highwater Aberdeen. To obtain a general view, a uniform scale is kept within the sec 
tion. Some stream figures, denoted by □ and A, have been enlarged (below left).