Not entirely sure what it means, but this is how it is commonly referred to. See e.g.:

"The sandbanks have a north-west to south-east orientation and are thought to be progressively, though very slowly, elongating in a north-easterly direction (perpendicular to their long axes) (Cooper et al., 2008). They extend from about 40km (22 nautical miles) off the north-east coast of Norfolk out to approximately 110km (60n miles) (Collins et al., 1995). (http://jncc.defra.gov.uk/ProtectedSites/SACselection/sac.asp... )

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Note added at 30 mins (2015-06-21 08:53:15 GMT)
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See also: "The banks are tidally-influenced estuary mouth sandbanks, the southern banks aligned approximately east-west in the direction of tidal currents entering the Thames Estuary from the English Channel whereas Long Sand is aligned in a north east - south west orientation with influence from the North Sea. In common with all sandbanks the structure of the banks is dynamic and there have been significant movements of the bank edges over time." (same web page)

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Note added at 35 mins (2015-06-21 08:58:21 GMT)
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I think I sort of understand it now. Try drawing it on a piece of paper; it helps to make it clearer.

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Note added at 1 hr (2015-06-21 09:23:18 GMT)
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NOTE: my second ref. is actually from here: http://jncc.defra.gov.uk/protectedsites/sacselection/habitat... (sorry, I posted the answer from my mobile phone)
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Note added at 1 hr (2015-06-21 09:31:09 GMT)
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this should clarify things somewhat:

"In his description of some Cretaceous sand banks Campbell (1971) noted bioturbated sets of cross-stratification with the facing direction of the foresets consistently directed towards the south-east, parallel to the former bank crests. The analogy with the Norfolk sand banks, located off the eastern coast of England, is close. These ***north-west to south-east oriented sand banks*** have sand waves moving north-westwards on the stoss slopes and predominantly south-eastwards on the preservable seaward facing lee slope, although it should be noted that the migration direction of sand waves on the upper parts of the stoss and lee slopes veers towards the Crestline (Fig. 4.25). Each of these modern sand banks has some resemblance to an elongate clockwise circulation cell of sand (Section 3.4.5), although not in the simple form envisaged by some workers (Swift, 1975)." ("Offshore Tidal Sands: Processes and deposits", By A. H. Stide: https://books.google.co.uk/books?id=UFMpBgAAQBAJ&pg=PT357&lp... )

=> "sandbanks with a north-west to south-east orientation"

can also be written as

"north-west to south-east oriented sandbanks")