142
Dt. hydrogr. Z. 44. 1991/92. H. 3. K 1c in et al.. Currents; German Bight
Additionally, the sediments are exposed to the lo-and-fro motion induced by surface waves.
The maximum velocity of these oscillatory currents reach 37 cm/s at 20 m depth for a 6-second
wave with a significant wave height of 2.3 nt — typical for this area. On January 25/26,' 1990,
a wave rider buoy westwards off Sylt (see Fig. 1) recorded a significant wave height of 5 in
and a period of about 9 s al a total depth of 19 m (Berger |199l|). The corresponding
maximum orbital velocities at the bottom are about 150 cm/s. Regarding the offshore wind
direction of the storm in the TOPEX area, the increase of sea stale is probably smaller, but
wave-induced near-bottom orbital currents up to about 100 cm/s can be assumed.
References
Berger. R. 1991: Seegangsmessungen in der
Deutschen Bucht im Jahre 1990. Meereskund-
liche Beobachtungen und Ergebnisse Band 71,
Bundesamt für Seeschiffahrt und Hydrogra
phie, Hamburg, 73pp.
DHI, 1988: Nautical cliarl No.89. Deutsches
Hydrographisches Institut, Hamburg.
Flemming, B . W. 1991; Zur holozänen Ent
wicklung. Morphologie und faziellen Glie
derung der oslfriesischen Insel Spiekeroog
(südliche Nordsee), Senkenberg-Am-Mecr,
Bericht 91/3, 51 pp.
Kontur, P. D. 1976: The Transport of Cohe-
sionless Sediments on Continental Shelves.
ln: D. J. Stanley and D. J. P. Swift (Ed.):
Marine Sediment Transport and Environmen
tal Management. New York; Wiley & Sons.
Nceman, V. 1990; Die Slunnflutcn im Januar
und Februar 1990 an der Westküste von
Schleswig-Holstein und in der Tideelbe. WSD
Nord. Dezernat für Gewässerkunde, 24pp.
Swift, D.J.P.,G. Parker, N. W. Lan-
f re d i , G. Pe r i 11 o and K. F i g g e 1978:
Shoreface-conneclcd Sand Ridges on Ameri
can and European shelves: A comparison.
Estuarine and Coastal Mar. Science 7, 257-
273.
Eingegangen am 18. März 1992
Angenommen am 8. Mai 1992
Anschrift der Verfasser:
Holger Klein
Dr. Ekkehard Mittelstaedl
Bundesamt für Seeschiffahrt und Hydrographie, Bcrnhard-Nocht-StraBe 78, 2000 Hamburg 36
