International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B7. Istanbul 2004 
of diaphragm wall and spurs ave certainly helped to check the 
erosion. Recently available high-resolution images will be 
extremely useful for such analysis. 
The knowledge about suspended sediment movement helps in 
understanding near-shore water flow. In one such study, a 
sediment plume emerging from the Kochi harbour made a sharp 
contact with the sediments along the coast indicating two different 
water masses. This clearly indicated that the plume is acting as 
obstruction to the sediment movement. This had resulted in 
erosion on the southern coast and deposition on the northern 
coast. The IRS P4 OCM data are extremely useful to study 
sediment dispersal and sediment transport studies due to their 2- 
day repeat cycle. The sequential nature of OCM helped in 
understanding sediment movement along the coast. OCM data has 
been used for computing advective velocity of surface currents 
(Prasad et al. 2002). 
5. MARINE WATER QUALITY 
Anthropogenic activities such as discharge of industrial and 
municipal sewage, land use, tourism, maritime transport, offshore 
oil exploration and production, dumping at sea degrade the 
marine environment. Turbidity, temperature and colour are 
indicators of water quality. Chlorophyll indicates trophic status, 
nutrient load and possibility of pollutants in coastal waters. 
Suspended sediments affect navigation, fisheries, and aquatic life, 
recreation potential of sea resorts. As the suspended sediments 
carry absorbed chemicals and fronts are associated with 
pollutants, the knowledge about their movement will help in 
predicting waste effluent transportation path. Suspended 
sediments are easily observed on the satellite imagery. Tides 
play an important role in the movement of suspended sediments 
and fronts (Nayak and Sahai, 1985). Successive images from IRS 
P4 OCM have been used for understanding impact of tides on 
sediments in. tide- and wave-dominated regions. A distinct front 
was observed separating the Gulf waters and the Arabian Sea, 
western India under different tidal conditions. This suggests that 
there is very little mixing between these two waters. Hence the 
pollutants discharged in the Gulf will circulate within the Gulf 
and ultimately will settle in the Gulf itself. 
Municipal sewage and industrial waste are major types of 
pollution observed on the coast. Toxic chemicals, nutrients, 
sediments and solid waste discharged in to coastal waters affect 
coastal ecosystems. Such waste out-falls are difficult to detect as 
near shore waters are turbid. Some of the effluents have colour 
and can be detected. One such waste out-fall from titanium 
factory near Thiruvananthapuram and sugar mill discharge near 
the Kakinada Coast, West and east coast of India were traced 
using high- resolution satellite data, respectively (Fig. 7). Indian 
coastal waters are relatively free from pollution except few 
pockets around industrialised zones and large cities. 
Oil spills from vessels and platforms are infrequent. In such cases, 
oil rises to surface and spread across the water body and thus 
amenable to remote detection. In one such study, IRS P4 OCM 
data was used for monitoring oil slick occurred in the Gulf of 
Kachchh. However, 2-day repeat cycle of OCM data is not 
adequate for monitoring slick in tide-dominated areas. Satellite 
surveillance is possible if high-resolution remote- sensing geo- 
synchronous satellite is available. Smaller spills from vessels, 
maintenance of oil infrastructure is a major source and is not 
detected on satellite images. Systematic observation with high- 
resolution satellite data will be helpful to study their effect on 
coastal habitats. 
  
Fig. 7. A plume from a sugar factory and its dispersion (dark 
colour) in the Kakinada Bay, Eastern India. 
Incidences of harmful algal blooms have increased worldwide. 
They may occur with cyclic regularity in certain regions where 
certain optimum environmental conditions prevail in marine 
waters. These planktons produce certain toxins, which adversely 
affect fish and other organisms. The bloom usually takes place 
rather suddenly and may spread with amazing speed, changing 
colour of surface water into red, green or hay colour. CZCS- 
derived chlorophyll map was used to study such bloom in the 
Baltic Sea. IRS P4 OCM data have been used to monitor 
Trichodesium bloom in the Arabian Sea using OCM data. 
6. MARINE ENVIRONMENT AND CLIMATE CHANGE 
The marine environment is sensitive and vulnerable to climate 
change. It is necessary to determine present status of the various 
systems and to predict future conditions. The high degree of 
uncertainty in present information inhibits effective management 
and limits the ability to make predictions and assess 
environmental change. Systematic collection of data on marine 
environment needed to apply integrated management approaches 
and predict effect of global climate change. Global climate change 
may compound pressures on coastal ecosystems through warmer 
sea surface temperature, altered ocean circulation patterns, 
changing storm frequency and rising sea levels. 
It was observed on IRS P4 images that productivity of the coastal 
waters of the Orissa coast increased after the cyclone (Nayak et al. 
2001). The frequency of cyclone has also increased during last 
several years. It may be interesting to see long-term impact on 
productivity in view of global warming. 
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