Shoreline change along Kerala, south-west coast of India, using geo-spatial techniques and field measurement

Coastal zone is a central attraction for coastal engineers, scientists and coastal community due to economic and developmental activities of the coast. Kerala has 593 km of coastline. More than 50% of the coast is occupied with artificial structures such as ripraps, groins, seawall, ports and fishing harbours. These coastal protection structures and developmental activities played a major role in altering the shoreline position significantly. Therefore, periodical analysis and monitoring of shoreline change is the primary requirement for effective planning and management of the coast. This paper provides the primary requirement of shoreline change rate for the past 26 years using geo-spatial technology and field investigation for proper management of the coast. Landsat 5 and 7, Resourcesat 1 and 2 and Cartosat-1 data set were used as primary data source. Long-term shoreline change rate (1990-2016) was calculated using weighted linear regression statistical method. The morphological study was carried out to substantiate the shoreline change pattern. For detailed investigation, the study area was divided into five sediment sub-cells. The analysis revealed that the maximum erosion of 54% was noticed in sediment sub-cells II, followed by IV (52%) and III (43%) respectively. The result also indicated that the accretion/erosion pattern of shoreline change on either side of breakwaters was varying from place to place. The effectiveness of the coastal protective seawall was very minimal. This indicates that proper planning of any artificial structures is the basic requirement for effective management of the coast. The overall shoreline change status of Kerala coast indicates that 45% of the coast is eroding and 34% of the coast is in stable condition. Only 21% of the coast is of accreting nature. The field survey was carried out to validate the analysed results for entire coast, specifically along the coastal structures. The study demonstrates that the combined effect of satellite data and field investigation can be a reliable approach for shoreline change analysis for these complex environments.