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DETECTION OF SHORELINE CHANGE DUE TO IMPACT OF BREAKWATERS

In Continuation and reference of: N.N. Salghuna, S. Aravind Bharathvaj (2015) Shoreline change analysis for the northern part of the Coromandel coast Elsevier aquatic proceedings volume:4 pg:317-324


The shorelines are a unique geographical feature and a major element used in Remote Sensing and coastal GIS providing key details on coastal landform dynamics. Shoreline change occurs every decade and creates its impact on coastal landforms. To observe these decadal changes - long sets of data, decadal monitoring of shorelines, and reasonable accuracy detection are essential. Construction of breakwaters and other natural factors negatively impact the shoreline by causing alterations resulting in Coastal erosion and accretion which indicates a very serious problem in the forthcoming years and should consider as a serious threat to the coastline environment. A comparative study is conducted for the 5 decades – (1980-1989, 1990-1999, 2000-2009, 2010-2019 & 2020-2029) to observe the decadal shoreline changes for shoreline length of approximately 91km from Puducherry to Karaikal. Landsat 4-5 TM, 8 OLI /TIRS, and Sentinel 2A satellite images were used to extract shorelines. (Digital Shoreline Analysis System) DSAS tool version 5.0, open-source software in ArcGIS is used for the shoreline analysis by casting transects for every 50 meters and stored in a table for proper understanding and analysis of Erosion and Accretion rates. These rates are then calculated by statistical analysis such as ( Linear Regression Rate) LRR and (Net Shore Movement) NSM. The results of this comparative study are shown in detailed graphs. The overall change of the coast shows that 58.94% of the area is affected by erosion and 41.06% of the area is affected by accretion.


The results show that the northern part is mainly affected by erosion and the southern part is mainly affected by accretion. The Puducherry coast covering 5 km on the southern side and 10 km on the northern side, overall 15 km has been greatly affected by the Ariyankuppam river's mouth breakwaters. The Cuddalore coast has undergone medium erosion around the Uppanar and Paravanar rivers. The Karaikal coast is noticed with medium erosion on the northern side and medium accretion on the southern side. During the decade 1980 – 1989, the analysis and results show that there wasn’t much accretion and there was a general trend of erosion in the coast. During the decade 1990 – 1999, the analysis and results show that there is a change in trend where the coast is been subjected more to accretion and subjected less to erosion. During the decade 2000-2009, the coast has undergone more erosion and comparatively less accretion. During the decade 2010 – 2019, the coast has undergone both erosion and accretion but erosion has undergone more during this decade compared to accretion. During the decade 2020 – 2029, the coast has undergone more erosion and accretion while comparing with the previous decade.


Work Credits: Nandanaa

Reference Credits: Aravind Bharathvaj Sridharan


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