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This paper is not intended to be a review of the subject of coastal
zone monitoring, rather it is an attempt to give a brief overview of
some of the research activities of members of this SIG, some of
which have been presented at the above meetings and at recent
Annual Conferences of the Association. For clarity, these have
been grouped under the three headings "water quality", "coastal
morphology" and "ecology and vegetation".
2. WATER QUALITY
2.1 State of the art
One of the more useful applications of remote sensing in coastal
areas is to monitor the volume, nature, concentration, distribution
and movement of suspended sediments and dissolved substances
by making use of their surface expression in the visible, thermal
infrared and even microwave parts of the electromagnetic
spectrum. Effluent and pollution, discharges and run-off may,
under favourable conditions, all be tracked, and movements of
sediment, particulary those linked to coastal erosion or accretion,
can be observed. Algal blooms are often associated with
concentrations of nitrates from agricultural activities and toxic
blooms may be prejudicial to the fishing industry. Oil slicks, both
accidental and deliberate, can be observed and hopefully, in the
not too distant future, they may be identified and logged in near-
real time on an operational basis.
Oil slicks can be readily detected in SAR imagery because of the
damping effect they have on the capillary surface waves. Much
effort is being expended on developing automated systems for
detection using for example the RAIDs processed ERS-1 data
from West Freugh. Cloud and land areas are masked out and then
likely areas (particularly in busy shipping lanes) are screened for
evidence of illicit oil dumping or tank cleaning and the results
supplied to the regulatory authorities such as the Coastguards and
Marine Pollution Units (Slogget and Jory, 1995; Slogget, 1994;
Bos et al., 1994). Large oil slicks can also be detected on AVHRR
imagery. Both the thermal signature and pattern recognition
techniques have been used to develop a "mixed oil slick
recognition algorithm" which was set up and tested on data from
the Haven tanker disaster in the Gulf of Genoa (Ulivieri and
Borzelli, 1994).
In the field of optical remote sensing main obstacles for
quantitative use in monitoring programmes are the lack of
operational atmospheric correction procedures and standardized
methods for calculation of water quality parameters from
atmospherically corrected data (Van Stokkom et al, 1993).
Determination of water quality parameters is generally based on
(semi-)empirical methods. Analytical procedures and methods for
integrating remote sensing with point measurements and
numerical models are now under development in a number of
recent projects.
For inland waters multi-temporally valid algorithms have been
established for chlorophyll-a and cyanophycocyanin (Dekker,
1995). For the estimation of seston dry weight (suspended
matter), Secchi depth transparency and vertical attenuation
coefficients semi-empirical algorithms are available, requiring in
situ measurements each time a remote sensing image is acquired.
The estimation of aquatic humus (dissolved organic matter) is
currently not possible for inland waters. Only through adequate
knowledge of the inherent optical properties of all the other
11
substances present in the water analytical algorithms for aquatic
humus determination may become available.
Going from inland waters to marine waters several changes
(mainly a decrease in concentrations) occur in the presence and
abundance of the various components within the water. When
(semi-)empirical methods are used in coastal zones, errors occur
in the estimation of water quality parameters, amongst others ‘due
to changes in the water surface state.
À number of member laboratories have been studying algal
blooms. These occur both in open waters (case 1 waters) and in
the coastal regions (case 2 waters). Much of the earlier work has
studied the ocean colour due to phytoplankton, algae and cyano-
bacteria. These are environmentally important generally but the
toxic algae are particularly important not only for the part they
play in the fish chain but because, if the come ashore, they can
also affect land animals and otherwise pollute the beach. Blooms
can quite easily be identified in case 1 waters by simple band
ratioing, but in coastal waters the presence of resuspended
sediment and bottom reflectance complicates the analysis. It is
found that the signatures obtained are very site-specific, and may
vary with time. This makes it difficult to specify a general
algorithm, as can be done for open waters, or to use such data to
classify algae types without in situ data for that particular area.
Since the demise of the Coastal Zone Colour Scanner in 1986 no
satellite ocean colour data has been available, but the delayed
deployment of the SeaWiFS (Sea Wide Angle of View Scanner)
and the imminent launches of ADEOS, carring OCTS (Ocean
Colour and Temperature Scanner) and ENVISAT carying MERIS
(Medium Resolution Imaging Spectrometer) should mean that
data will become available in the future. Aircraft are particulary
useful, however, for coastal monitoring. Not only is the spatial
resolution more suited to such work, but the new hyperspectral
scanners now being flown and the temporal flexibility of aircraft
enable them to image subtleties not possible from satellites
(Vaughan, 1995).
The National Rivers Authority regularly flies the coastline of
England with a CASI system which is programmed to simulate
the SeaWiFS channels. This data is being used at the Dundee
Centre for Coastal Zones Research, together with other datasets
such as AVHRR and its own VIFIS (Variable Interference Filter
Imaging Spectrometer) data, in a feasibility study for the British
National Space Centre on the operational use of EO data for algal
bloom monitoring. Stockholm University has studied blooms in
the Baltic using AVHRR and the Joint Research Centre in Ispra
has mapped the biologically active areas in the Mediterranean
from archived CZCS data (Barale and Schlittenhardt, 1994); Rud
and Kahru, 1995).
Other projects being undertaken in Dundee, which have
implications for coastal polution, is the development of an
automatic ship detection system using RAIDS ERS-1 SAR data in
near-real-time and the study of thermal outfalls (Vaughan et al.,
1995).
Methods for derivation of water quality parameters from remote
sensing data should not only be multi-temporally valid, but also
be applicable to the data from different sensors. In view of the
present developments towards airborne and in the near future
even spaceborne imaging spectrometry systems, data processing
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B6. Vienna 1996
