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.  Meereskundliche
  Beobachtungen  und  Ergebnisse  Band  71,
Bundesamt  für  Seeschiffahrt  und  Hydrographie, ­
  Hamburg,  73pp.
DHI,  1988:  Nautical  cliarl  No.89.  Deutsches
Hydrographisches  Institut,  Hamburg.
Flemming,  B  .  W.  1991;  Zur  holozänen  Entwicklung. ­
  Morphologie  und  faziellen  Gliederung ­
  der  oslfriesischen  Insel  Spiekeroog
(südliche  Nordsee),  Senkenberg-Am-Mecr,
Bericht  91/3,  51  pp.
Kontur,  P.  D.  1976:  The  Transport  of  Cohesionless
  Sediments  on  Continental  Shelves.

ln:  D.  J.  Stanley  and  D.  J.  P.  Swift  (Ed.):
Marine  Sediment  Transport  and  Environmental ­
  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.  Lanf
  re  d  i  ,  G.  Pe  r  i  11  o  and  K.  F  i  g  g  e  1978:
Shoreface-conneclcd  Sand  Ridges  on  American ­
  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