Shoreline changes and morphology of spits along southern Karnataka, west coast of India: A remote sensing and statistics-based approach

Abstract

The changes in shoreline positions and morphology of spits along the Karnataka coast, western India, are investigated for the period from 1910 to 2005 using multi-dated satellite images and topomaps. The study area has been divided into four littoral cells, and each cell into a number of transects at uniform intervals. The rate of change in shoreline position has been estimated using the statistical linear regression method and cross-validated with regression coefficient ( R 2) and Root Mean Square Error (RMSE) methods. Past and future shoreline positions have been demarcated and future positions of shoreline are estimated for time periods of 10- and 24-years. The study reveals that (i) about 57% of transects exhibit ± 10 m RMSE values, indicating better agreement between the estimated and satellite-based shoreline positions, and (ii) transects closer to the cell boundaries exhibit about 50% uncertainties in shoreline change rate estimations. Based on RMSE values, the influence of natural processes and anthropogenic factors on shoreline changes has been evaluated. The cells/transects dominated by natural processes reveal low RMSE values, whereas the cells/transects influenced by anthropogenic activities such as sand mining, construction of coastal structures, exhibit higher RMSE values. However, the variation in RMSE values is not significant if the total number of transects is considered. Significant changes in morphology of spits have been recorded. Spits demonstrate variations in areal extent, i.e., length and area, if 1910 and 1967 are considered separately as base years. The present study demonstrates that combined use of satellite imagery and statistical techniques such as linear regression and RMSEs can be very useful in quantifying shoreline changes and spit morphology.