Operational forecast of oil spill trajectory and assessment of impacts on intertidal macrobenthos in the Dahanu region, west coast of India

Abstract

A two-dimensional model has been developed and applied to the hypothetical spills of crude oil in the Dahanu area on the west coast of India. An attempt has also been made to quantify the intertidal macrobenthic biomass and population affected in the region. Data on tides and currents were collected at Dahanu during October and November 2008. The currents recorded at a relatively offshore location show that the midcurrents were stronger than the bottom currents. The currents at a nearshore location were influenced by the Dahanu creek currents. Offshore currents were relatively stronger than the nearshore currents. The model calibration results of hydrodynamics show that the circulation was almost in agreement with the observations except in the creek zone. An oil spill model was run for two weather conditions, viz., postmonsoon and monsoon. An instantaneous crude oil spill of 500 tons (534 m sup(3)) was considered. The results show that the spill would move offshore in the presence of postmonsoonal winds. However, during the monsoon, the spill would move toward the coast. According to the positions of the occurrence, the spill would reach the coast within 13 to 28 hours from the time of spill. The coastline stretches an affected range from 2.1 to 2.8 km. The estimated affected macrobenthic biomass and population would be 109.2 to 145.6 kg and 1.9 to 2.5x10 sup(7), respectively. The major species affected would be polychaetes.