Assessment on Shoreline Retreat in Response to Sea Level Rise - Chennai Coast

In the present condition, the rise in sea level due to climate change is a serious threat for the environment. Global average sea levels are predicted as 1.8 mm/y during 1870-2009 and nearly 2.8 mm/y along the Indian Coast by Intergovernmental Panel on Climate change (IPCC). Impacts of rise in sea-level will be the loss of land in coastal areas through erosion, submergence of the coastal landscape and the threat of inundation. Shore erosion causes the shoreline to retreat and this leads to affecting the erosion zone by moving the shoreline inland. In this study, the attempt is made to demarcate the impact of sea level rise along the Chennai coast (Tamil Nadu) located along the southeast coast of India. This area experiences threat from many disasters such as storm, cyclone, flood, tsunami and long-term sea level rise. The shoreline has been extracted and using DSAS tool in ArcGIS, long-term (1990-2012, 1990-2013, 1990-2014, 1990-2015 and 1990-2016) were analyzed using Linear regression Rate and Weighted Linear Regression. 36.7% of the coast was seen with eroding condition. Overall long-term analysis trend suggest that more than 60% of the region falls in stable to low accretion. Projection of climate change-induced SLR at different RCPs (2.6, 4.5, 6, 8.5) of IPCC AR5 on different time scale (2025, 2050, 2075, 2100) for the coasts of Chennai. The values range from 7.1 cm to 36.87 cm for RCP 2.6; 7.37 cm to 49.84 cm for RCP 4.5; 7.16 cm to 51.75 cm for RCP 6; 7.38 cm to 77.88 cm for RCP 8.5. Shoreline retreat to an increase in local sea level was mapped using the Bruun Rule. Since the Bruun Rule (BR) has some limitations, the modified Bruun rule was used to analyze the inundation factor. The area of horizontal inundation is estimated as similar to 1.6 km (Braun rule) and similar to 1.1 km (Modified Bruun Rule). The required data was processed using GIS environment. Since we adhere to the fact that the coastal change is not a periodical accumulation per year, but that it entraps a value of future crisis assessment and gives a literal warning about the shore to be persevered.