Coastal erosion triggered by a shipwreck along the coast of Goa, India

Temporal satellite imageries (1999, 2001, 2003, 2006, 2008 and 2011), wave model (DHI) results and field measurements have been used to evaluate whether the grounded ship MV River Princess played a role in triggering erosion along the famous Candolim-Sinquerim beaches of Goa. Coastal sand dunes bore the maximum impact. The cause of the erosion is unique. The orientation of the ship with respect to the coastline, its length, the distance of the ship from the coastline and, more importantly, the direction of the waves prevailing over the region suggest that the wreck acted like an offshore breakwater and triggered erosion along this coast. A tombolo was also formed on the lee side of the vessel, a process that eventually led to the formation of an accretion zone on the lee side. The zone of deposition is evidenced by the presence of a sand bar which gets partially exposed during low tide. As the littoral current along this coast is southward, the sand bar blocked the southward littoral drift. As a consequence, the sand depletion that followed subsequently induced erosion of the sea front. The extent of net erosion has been estimated at around 0.10934 sq. km (109,340 sq. m) during the past 12 years. A stretch of 1.5 km of the coast has receded by a maximum of 85 m. In economic terms, the loss of prime property is estimated at minimum 28 crore rupees. The direct impact of the wreck in eroding the coast is more explicit during the SW monsoon. The powerful intensity of winds and higher significant wave height (H-s = 2.59 m) during the SW monsoon deteriorate the shore front that is now devoid of sand dunes and, as a consequence, has gradually become fragile due to severe erosion.