Nearshore Coastal Processes Between Karwar and Bhatal, Central West Coast of India: Implications for Pollution Dispersion

Abstract

In the present paper coastal processes between Karwar and Bhatkal, Central West Coast of India is discussed based on the Indian Remote Sensing program – 4 Ocean Color Monitor (IRS P4-OCM) data, wind and wave data and wave refraction derived near shore drift pattern, salinity condition and beach morphological changes. Near shore pollution dispersion pattern is inferred for the coastal region between Karwar and Bhatkal based on the observed coastal processes. Prevailing salinity conditions suggest upwelling during pre-monsoon to early monsoon, but become less effective during late monsoon, and down welling become important during winter. The upwelling are related to the combined effect of local wind and regional northward subsurface flow due to regional phenomena during pre-monsoon; South West-West approach of the waves for North -North West oriented coast and winter cooling effect during November and December respectively. The prevailing calm weather conditions due to low wave activities during December-January months facilitate tidal currents to dominate. The tidal currents move the water body towards seaward. Seasonal variations in the beach profiles indicated seaward movement of materials during monsoon, landward movement during post-monsoon and wave induced circulation patterns during pre-monsoon. In the vicinity of the river mouths, however, movement of the materials is dominantly northward. Sediments on the beach ranged from fine to medium grained, moderately to well sorted, which suggest dominance of waves on the coastal processes. Wave refraction derived alongshore drift pattern reveal seasonal variation in the direction of the current. IRS-P4 OCM data revealed 3 distinct pattern of sediment dispersion. Trend 1- during early monsoon, plume like sediment dispersion seaward especially in the mouths of the rivers; Trend 2- with the onset of monsoon, there is northerly transport of sediments with anticlockwise pattern with in the linear plumes; Trend-3 during post-monsoon, sediment concentration is less and it is southward. These patterns can be used to trace pollutants dispersion in the coastal sea.