32
3 Study Area
oog backbarrier area, the Otzumer BalJe, with a depth of up to 17 m, current velocities of O.7~ 1.3 m Sl were measured (Bartholoma & Flemming 1993). The velocities above the tidal tlats reach values up to 0.3 m Sl (Bartholoma 1993). A
further essential factor forming the morphology in the area of the main inlet is
swell, storm waves in particular, which enter the Otzumer Balje from NW
(Chap. 3.3). In the long-term, the shift and changes in the size of the catchment
areas of the tidal basins cause a gradual modification of hydrodynamic conditions.
Sedimentation processes are in turn themselves influenced by these variations
(Walther 1972; Fitzgerald et al. 1984; Sha & Berg 1993).
In July 1994, March 1995, September 1995, April 1996 and October 1996 a
100 m grid was established on the Swinnplate with a laser theodolite (90 measurement points; Bartholoma, Flemming unpub!. data). The measurements from 1995
and 1996 were converted to mean sea level. For each measurement location, the
differences in height between two consecutive measurement campaigns were integrated and summed up for the calculation of volume balances over the area of
every measurement unit (lOx 10' m\
In October 1994 an area of 1.5 km
2
on the Groninger Plate was surveyed topographically with a grid distance of 125 m and converted to mean sea level (Bartholoma, Flemming unpubl. data). These data were compared with topographical
maps of this area from 1964, 1975 and 1990.
The Swinnplate can be subdivided morphologically into three different areas
(Bartholoma, Flemming unpub!. data). The western area changes mainly during
wintertime, however, it stabilizes its relief during the summer. The middle, deeper
area is covered by small tidal gullies and shows a strong seasonality in topography.
The eastern area is a little more elevated and is intluenced by biodeposits of the
local mussel beds mainly in the summer months. Topographic changes of the
Swinnplate, with spatially and temporally variable mussel settlements, show a
good spatial agreement with the accumulation of biodeposits in the summer
months and their erosion in winter (Sect. 3.4.4).
This seasonal cycle was disturbed by the strong ice winter of 1995/96. After total loss of the mussel beds and locally massive erosion, biodeposition was missing
in the early summer and the area was merely subject to hydrodynamic conditions.
Nevertheless, the morphology was re-established again approx. within 6 months
after the ice winter (Bartholoma, Flemming unpubl. data). This relatively fast
reorganization of the morphology after extreme events occurs following the prevailing hydrodynamic conditions and is therefore controlled by the large-scale
geomorphology of the tidal basin (Oost & De Boer 1994; Nyandwi 1995; Eitner
1996).
The relief and location of the Grl)ninger Plate has remained relatively stable
over a period of 30 years (Bartho10ma, Flemming unpub!. data). The dynamic of
this relief which slopes slightly to the north-west, documents a close link to hydrodynamic parameters. The slight decrease in topographical height indicates an increase in strong wind events (Fach 1996). Since the Groninger Plate, unlike the
Swinnplate, is almost solely subject to hydrodynamic influences, it is suitable as an
indicator for longer-term modifications of physical water parameters and resulting
morphological changes (Bartholoma, Flemming unpub!. data). Changes on the
Swinnplate, however, occur in much shorter intervals and vary seasonally.
3 Study Area
oog backbarrier area, the Otzumer BalJe, with a depth of up to 17 m, current velocities of O.7~ 1.3 m Sl were measured (Bartholoma & Flemming 1993). The velocities above the tidal tlats reach values up to 0.3 m Sl (Bartholoma 1993). A
further essential factor forming the morphology in the area of the main inlet is
swell, storm waves in particular, which enter the Otzumer Balje from NW
(Chap. 3.3). In the long-term, the shift and changes in the size of the catchment
areas of the tidal basins cause a gradual modification of hydrodynamic conditions.
Sedimentation processes are in turn themselves influenced by these variations
(Walther 1972; Fitzgerald et al. 1984; Sha & Berg 1993).
In July 1994, March 1995, September 1995, April 1996 and October 1996 a
100 m grid was established on the Swinnplate with a laser theodolite (90 measurement points; Bartholoma, Flemming unpub!. data). The measurements from 1995
and 1996 were converted to mean sea level. For each measurement location, the
differences in height between two consecutive measurement campaigns were integrated and summed up for the calculation of volume balances over the area of
every measurement unit (lOx 10' m\
In October 1994 an area of 1.5 km
2
on the Groninger Plate was surveyed topographically with a grid distance of 125 m and converted to mean sea level (Bartholoma, Flemming unpubl. data). These data were compared with topographical
maps of this area from 1964, 1975 and 1990.
The Swinnplate can be subdivided morphologically into three different areas
(Bartholoma, Flemming unpub!. data). The western area changes mainly during
wintertime, however, it stabilizes its relief during the summer. The middle, deeper
area is covered by small tidal gullies and shows a strong seasonality in topography.
The eastern area is a little more elevated and is intluenced by biodeposits of the
local mussel beds mainly in the summer months. Topographic changes of the
Swinnplate, with spatially and temporally variable mussel settlements, show a
good spatial agreement with the accumulation of biodeposits in the summer
months and their erosion in winter (Sect. 3.4.4).
This seasonal cycle was disturbed by the strong ice winter of 1995/96. After total loss of the mussel beds and locally massive erosion, biodeposition was missing
in the early summer and the area was merely subject to hydrodynamic conditions.
Nevertheless, the morphology was re-established again approx. within 6 months
after the ice winter (Bartholoma, Flemming unpubl. data). This relatively fast
reorganization of the morphology after extreme events occurs following the prevailing hydrodynamic conditions and is therefore controlled by the large-scale
geomorphology of the tidal basin (Oost & De Boer 1994; Nyandwi 1995; Eitner
1996).
The relief and location of the Grl)ninger Plate has remained relatively stable
over a period of 30 years (Bartho10ma, Flemming unpub!. data). The dynamic of
this relief which slopes slightly to the north-west, documents a close link to hydrodynamic parameters. The slight decrease in topographical height indicates an increase in strong wind events (Fach 1996). Since the Groninger Plate, unlike the
Swinnplate, is almost solely subject to hydrodynamic influences, it is suitable as an
indicator for longer-term modifications of physical water parameters and resulting
morphological changes (Bartholoma, Flemming unpub!. data). Changes on the
Swinnplate, however, occur in much shorter intervals and vary seasonally.