57
Storm Impact on the Coastal Geomorphology and Current Field
3.6 APPLICATIONS AND APPLICABILITY OF DiSC
DiSC could be part of a coastal monitoring system that could be combined with
bathymetric ship surveys or other remote sensing and in situ methods. Despite the
fact that the DiSC depth accuracy is one order of magnitude lower in comparison
with the in situ surveys, DiSC has several advantages. In contrast to the side scan
sonar campaigns are the quasi-instantaneous measurement and the ability to measure
during extreme storm conditions, so at times at sandy coasts, the highest morphodynamical changes occur. Presumably, it could be stated that a combination of the
two methods delivers the most valuable output as temporally coarse, cost-expensive
but highly accurate side scan data sets. These are to be completed with temporally
fine DiSC water depth maps. As with DiSC, current vector maps can be retrieved by
high-frequency (HF) radars. HF radars measure on a coarser spatial scale and are
therefore not competing. All other methods are point or measurements that measure
the current vector mechanically or acoustically. An extensive comparison of the current measurement instruments is given by Lane et al. (1999). For complex bathymetries and current regimes, spatial methods can deliver eddy features that are not
detectable by point measurement devices.
As the study case of Sylt Island proved, the application of DiSC would offer
potential advantages to the different user communities:
1. Coastal and offshore engineering. The impact of offshore structures and
morpho-dynamic processes should be studied.
2. Coastal protection. Shallow-water sandy bathymetries should be monitored
in order to trigger protection activities in time.
3. Harbor authorities. Exposed harbor entries can be monitored upon local
current regimes that are critical for shipping traffic.
4. Numerical modeling. Spatial DiSC data can be utilized for validation,
fusion, and assimilation of numerical model data.
5. Search and rescue. With current vector data, the drift of an object can be
targeted and could be used for the optimization of rescue operations.
3.7 CONCLUSIONS
DiSC determines the water depth utilizing shallow water waves and the surface
current vector fields from both shallow- and deep-water waves. Therefore, DiSC is
applicable in shallow waters for water depth measurements and in any waters retrieving the surface current field under the assumption of wave field stationarity. For the
determination of the bathymetry, long waves (e.g., a swell system) are necessary as
carriers of the bathymetric information. As they approach the coastal zones, they
are refracted due to the local depth, and by inverting their spectral properties, the
depth could be retrieved. In contrast, the effect of the current on the wave spectrum
is proportional to the wave number. It is more effectual for short-wind sea waves than
for long swells. In summary, DiSC provides bathymetric and current field measurements, with known limitations when the environmental conditions become critical
for the rest of the in situ measuring devices in the littoral zone.
Storm Impact on the Coastal Geomorphology and Current Field
3.6 APPLICATIONS AND APPLICABILITY OF DiSC
DiSC could be part of a coastal monitoring system that could be combined with
bathymetric ship surveys or other remote sensing and in situ methods. Despite the
fact that the DiSC depth accuracy is one order of magnitude lower in comparison
with the in situ surveys, DiSC has several advantages. In contrast to the side scan
sonar campaigns are the quasi-instantaneous measurement and the ability to measure
during extreme storm conditions, so at times at sandy coasts, the highest morphodynamical changes occur. Presumably, it could be stated that a combination of the
two methods delivers the most valuable output as temporally coarse, cost-expensive
but highly accurate side scan data sets. These are to be completed with temporally
fine DiSC water depth maps. As with DiSC, current vector maps can be retrieved by
high-frequency (HF) radars. HF radars measure on a coarser spatial scale and are
therefore not competing. All other methods are point or measurements that measure
the current vector mechanically or acoustically. An extensive comparison of the current measurement instruments is given by Lane et al. (1999). For complex bathymetries and current regimes, spatial methods can deliver eddy features that are not
detectable by point measurement devices.
As the study case of Sylt Island proved, the application of DiSC would offer
potential advantages to the different user communities:
1. Coastal and offshore engineering. The impact of offshore structures and
morpho-dynamic processes should be studied.
2. Coastal protection. Shallow-water sandy bathymetries should be monitored
in order to trigger protection activities in time.
3. Harbor authorities. Exposed harbor entries can be monitored upon local
current regimes that are critical for shipping traffic.
4. Numerical modeling. Spatial DiSC data can be utilized for validation,
fusion, and assimilation of numerical model data.
5. Search and rescue. With current vector data, the drift of an object can be
targeted and could be used for the optimization of rescue operations.
3.7 CONCLUSIONS
DiSC determines the water depth utilizing shallow water waves and the surface
current vector fields from both shallow- and deep-water waves. Therefore, DiSC is
applicable in shallow waters for water depth measurements and in any waters retrieving the surface current field under the assumption of wave field stationarity. For the
determination of the bathymetry, long waves (e.g., a swell system) are necessary as
carriers of the bathymetric information. As they approach the coastal zones, they
are refracted due to the local depth, and by inverting their spectral properties, the
depth could be retrieved. In contrast, the effect of the current on the wave spectrum
is proportional to the wave number. It is more effectual for short-wind sea waves than
for long swells. In summary, DiSC provides bathymetric and current field measurements, with known limitations when the environmental conditions become critical
for the rest of the in situ measuring devices in the littoral zone.