36
Multiscale Hydrologic Remote Sensing: Perspectives and Applications
On the north side of the area of interest, there is a main shipping channel, Lister
Tief. The width of this tidal channel is 2.5 km and its depth exceeds 30 m. At its bottom, there are sand dunes having a 200–500 m wavelength and 5–10 m-height and
migrating about 80 m per year (Hennings et al. 2004). The west side of the island,
toward the open sea, is characterized as a strand plain, but at the isoline of 3 m, there
is a long-shore bar, which has great seasonal, annual, and hyperannual variability in
time and space. In addition, on the northwestern side of the island, there is a relatively shallow, maximum-depth 12-m shipping channel, the Lister Landtief. Between
the two channels, there are several shoals, where the wave field is refracted, and the
wave field loses its energy by breaking. The tidal inlet is considered wave protected.
Figure 3.1 illustrates all the geomorphological details, and the white square marks
the exact area of interest.
The typical hydrodynamics of the island are dominated by a semidiurnal lower
to upper mesotidal regime with a tidal range of 1.8–2.2 m (Backhaus et al. 1998). In
the deep traffic channels to the west of List West, the current velocities measured
by an acoustic Doppler current profiler (ADCP) are between 0.2 and 1.2 m/s with a
moderate breeze condition (3–4 Beaufort; Cysewski 2003). Similar measurements,
at the tidal inlet and in the tidal channel at the north of Ellenbogen, demonstrated a
maximum near-surface current velocity of 2.0 m/s. High-resolution radar and shipbased measurements have shown the significant impact of the bathymetry and of the
submarine geostructures on the current field (Kakoulaki 2009). The westerly winds
are dominant (Mueller 1980; Ahrendt 2001). The wave measurements at a depth of
12 m offshore Westerland have shown that the dominant wave direction is west–
southwesterly during normal conditions and westerly during storm conditions. The
mean wave height is calculated from the available data as 1.5 m, with a maximum
value of 5 m (BSH 2009).
In the inlet, the tidal currents cause cross-shore transport through the channel
between the barrier islands. At the west side of the island, tidal and wave-induced
currents are dominant seaward of the long-shore bar, resulting in sediment suspension and transport to the north (Sistermans and Nieuwenhuis 2004). The longshore transport along the coast depends on the approaching angle of the waves
to the shore. With foreshore normal or slightly oblique waves and a long-shore
variation in wave height, a cell circulation system is generated. Judging from the
orientation of the coast and the lack of embayment and cusps along the beach, it
seems that usually the waves break with an appreciable angle with respect to the
shore; therefore, the flow is dominated by a long-shore directed current, and the
circulation cells have not been observed in the spatial scale of the experiment
(Figure 3.1). In general, the near-shore flow is the complex, synergic result of the
waves and tides, so in any case, the impact of the water circulation is the continuous erosion and movement of the sediment offshore and to the northern end of the
island.
3.1.2 exPeRiMental SetuP
The complexity of the natural environment requires synergetic monitoring by several systems. Radar data sets are acquired by Helmholtz-Zentrum Gessthacht (HZG)
Multiscale Hydrologic Remote Sensing: Perspectives and Applications
On the north side of the area of interest, there is a main shipping channel, Lister
Tief. The width of this tidal channel is 2.5 km and its depth exceeds 30 m. At its bottom, there are sand dunes having a 200–500 m wavelength and 5–10 m-height and
migrating about 80 m per year (Hennings et al. 2004). The west side of the island,
toward the open sea, is characterized as a strand plain, but at the isoline of 3 m, there
is a long-shore bar, which has great seasonal, annual, and hyperannual variability in
time and space. In addition, on the northwestern side of the island, there is a relatively shallow, maximum-depth 12-m shipping channel, the Lister Landtief. Between
the two channels, there are several shoals, where the wave field is refracted, and the
wave field loses its energy by breaking. The tidal inlet is considered wave protected.
Figure 3.1 illustrates all the geomorphological details, and the white square marks
the exact area of interest.
The typical hydrodynamics of the island are dominated by a semidiurnal lower
to upper mesotidal regime with a tidal range of 1.8–2.2 m (Backhaus et al. 1998). In
the deep traffic channels to the west of List West, the current velocities measured
by an acoustic Doppler current profiler (ADCP) are between 0.2 and 1.2 m/s with a
moderate breeze condition (3–4 Beaufort; Cysewski 2003). Similar measurements,
at the tidal inlet and in the tidal channel at the north of Ellenbogen, demonstrated a
maximum near-surface current velocity of 2.0 m/s. High-resolution radar and shipbased measurements have shown the significant impact of the bathymetry and of the
submarine geostructures on the current field (Kakoulaki 2009). The westerly winds
are dominant (Mueller 1980; Ahrendt 2001). The wave measurements at a depth of
12 m offshore Westerland have shown that the dominant wave direction is west–
southwesterly during normal conditions and westerly during storm conditions. The
mean wave height is calculated from the available data as 1.5 m, with a maximum
value of 5 m (BSH 2009).
In the inlet, the tidal currents cause cross-shore transport through the channel
between the barrier islands. At the west side of the island, tidal and wave-induced
currents are dominant seaward of the long-shore bar, resulting in sediment suspension and transport to the north (Sistermans and Nieuwenhuis 2004). The longshore transport along the coast depends on the approaching angle of the waves
to the shore. With foreshore normal or slightly oblique waves and a long-shore
variation in wave height, a cell circulation system is generated. Judging from the
orientation of the coast and the lack of embayment and cusps along the beach, it
seems that usually the waves break with an appreciable angle with respect to the
shore; therefore, the flow is dominated by a long-shore directed current, and the
circulation cells have not been observed in the spatial scale of the experiment
(Figure 3.1). In general, the near-shore flow is the complex, synergic result of the
waves and tides, so in any case, the impact of the water circulation is the continuous erosion and movement of the sediment offshore and to the northern end of the
island.
3.1.2 exPeRiMental SetuP
The complexity of the natural environment requires synergetic monitoring by several systems. Radar data sets are acquired by Helmholtz-Zentrum Gessthacht (HZG)