Aquatic Pollution and Coastal Management

Unit 14 : Coastal zone management and information system

14.7.2. Study of oceanic and coastal water (physical) properties
The introduction of microwave satellites with the existing operational satellites, increased the potentiality to a great extent in studying the dynamics of coastal waves and currents, surface wind speed, sediment plumes, mapping of bottom topography, coastal bathymetry (to 20 mts. depth) and identifying the potential zone of fishing grounds in the offshore based on the study of ocean colour, sea surface temperature (thermal gradients/fronts), upwelling zones (results of divergence and offshore currents) etc.

In the visible portion of the EM spectrum radiation, is able to penetrate water surface to a certain extent (unlike in the infrared or microwave region) and is reflected by suspended manner present in the water. Sequential imagery may be used for qualitative analysis of the suspended sediments in the areas of enhanced coastal estuarine erosion.

Planktonic matter in surface water is readily detected by Remote Sensing technology due to strong spectral signatures of ‘chlorophyll-a’ which is the pigment responsible for photosynthesis. Remotely sensed measurement of ‘chlorophyll-a’ and hence phytoplankton biomass is well established by various investigators.
Anomalous low salinity and temperature conditions are indicative of upwelling. During upwelling, subsurface waters of relatively low oxygen content ascends to the surface and the surface water may become markedly under saturated. Upwelling zones are known to be highly productive regions due to the increased supply of nutrients brought into the euphotic zone from below. Upwelling in thermal front regions (sharp boundaries between water masses by temperature gradient) has high potential as fishing grounds for pelagic species especially ‘tuna’. SST and Ocean Colour maps can thus guide fishing vessels to areas of high potential, thereby saving considerable time and fuel. RS and GIS based coastal environmental information system has already been adopted in some of the South/Southeast Asian countries and Australia as a basis for resources inventories, marine habitat assessment, coastal zone planning and management and environmental education. In Indian scenario, a number of online projects are coming up from different government departments, both in state and central levels.
The imageries are found to be useful in providing information on bottom topography/bathymetry in highly specific conditions of sea state and currents, and hence are unlikely to provide an operational means for routine mapping of bottom topography or bathymetry mapping.

Geostationary satellites and polar satellites are now being widely used for tropical cyclone monitoring in terms of surface wind fields, warm core observations etc.