According to the topographic chart of the seabed from soundings taken by the German FederalMaritime and Hydrographic Agency in 1991 the water depth at the site is approximately 23 m. A seismic research trip by the FS Alkor in May 2006 confirmed these soundings in principle, but registered depths that were generally about one meter less.
During the site investigation a water level of 22.2 m was measured, which according to tidal adjustment by the German FederalMaritime and Hydrographic Agency, produces a lowest astronomical tide (LAT) of 21.8 m.
The lowest astronomical tide (LAT – equivalent to the newer marine chart zero) was estimated from the coastal levels and assumed to be 0.2 m below low tide. According to information provided by the German Federal Maritime and Hydrographic Agency, the height of the highest astronomical tide (HAT) extrapolated from North Friesian levels is 2 m above low tide. Storm surge of 2.6 m should be included in the reckoning according to model calculations from the MUSE project of the German Federal Maritime and Hydrographic Agency.
This results in a theoretically possible maximum water level of 4.6 m above low tide or a maximum water depth of 26.6 m.
The design water level need not however be configured at the most unfavourable case of a very improbable coincidence of a maximum storm surge and the highest astronomical tide (together with the design wave). The maximum tide is therefore reduced by 0.3 m for this water level.
|Water level||at LAT||absolute|
|LAT - marine chart zero||0 m||21.8 m|
|low tide||+0.2 m||22 m|
|high tide||+1.2 m||23 m|
|HAT||+2.2 m||24 m|
|storm surge||+2.6 m||max 26.6 m|
|still water level||+4.5 m||26.3 m|
At SWL (26.3 m) the wave crest reaches heights of up to 14 m (40.3 m above ground or 18.5 m above marine chart zero).
The parameters of the design wave and of the 30- and 10-year high were set as follows:
|parameters||50 years||30 years||10 years|
|design water depth||d||26.3 m||26.3 m||26.3 m|
|designated wave height||H1/3||9.2 m||8.9 m||8.3 m|
|designated wave height||Hmax||17.9 m||17.3 m||16.2 m|
|wave crest above marine chart zero||HSWL+η||18.0 m||17.7 m||16.4 m|
|wave lengths||l||170 - 232 m||166 - 224 m||158 - 216 m|
|wave periods||TD||10.7 - 13.9 s||10.6 - 13.6 s||10.2 - 13.1 s|
This is based on statistical records of the WaveRider wave buoy NSBII of the German Federal Maritime and Hydrographic Agency from the years 1993-2006.
According to these records the main heading of the waves is west-southwest, the extreme events however generally occur with west to north-westerly directions as here the fetch is particularly great. Here, figures coming very close to the aforementioned 50-year figures for significant wave height were achieved in just 13 years.