The most severe storm passing Denmark in the 20th century occurred on 3-4 D
ecember 1999. During this event, waves, currents and suspended sediment con
centrations were measured on a muddy tidal flat vis-vis the salt marsh of S
kallingen in the inner part of the Hobo Dyb tidal area on the Danish west c
oast. Locally generated wave heights increased during the storm to H-3=0.38
m, with peak spectral wave periods of up to 3.6 s and wave-induced bed she
ar stresses reaching a maximum of about 2 N m(-2). The highest current velo
city measured over the tidal flat during the surge was 0.64 m s(-1) (simila
r to1 N m(-2)). During the surge peak, the wind-induced water circulation c
lose to the bed was about 0.2 m s(-1) which is equivalent to a bed shear st
ress of about 0.2 N m The concentration of suspended matter on the tidal fl
at increased from about 10 mg 1(-1) to about 200 mg 1(-1), and the mobile l
ayer on the mud flat was removed. The estimated deposition on the salt mars
h amounted to 133 g m(-2) (0.15 mm) which is only about 50% higher than tha
t of a previously monitored gale event, and corresponds to less than 10% of
the yearly deposition at the site.
It is suggested that deposition on the salt-marsh surface caused by storms
or gales depends on the prevailing meteorological and hydrographical condit
ions as well as on the sequence of previous import and high-energy events.
The results indicate that a single extreme storm can be of less importance
for annual variations in saltmarsh deposition than more regularly occurring