Date of Award

31-8-2024

Document Type

Thesis

School

School of Civil Engineering

Programme

Ph.D.-Doctoral of Philosophy

First Advisor

Dr.S.E.Saranathan

Keywords

Pre and Post Tsunami, Tsunami Sediments, Coastal Sediments, Tamil Nadu, Granularity, Textural Parameters, Granule, Angularity, Roundness, Heavy Minerals, Provenance

Abstract

Tsunamis represent some of the most devastating natural events for coastal regions, as exemplified by the 26th December 2004 Great Indonesian Earthquake triggered a massive tsunami across the Bay of Bengal and Indian Ocean, causing extensive destruction in various countries, including India. This study addresses a significant gap in the literature by focusing on the detailed sedimentological aspects of coastal dynamics. Specifically, it examines the pre-tsunami (December 2004), post-tsunami (January 2005), and recent (December 2022) sediment characteristics along a 35 km stretch of the Coromandel coast from Poompuhar to Nagoor.

Eight stations were selected for sampling: Poompuhar, Chinnankudi, Kuttyandiyur, Chandrapadi, Kottucherimedu, Karaikal Beach, Vadakku Vanjiyur North, and Nagoor Beach. The study area is characterized by various geomorphic features, including deltas, flood plains, and paleochannels, with principal rivers such as the Cauvery, Nandalar, and Arasalar emptying into the Bay of Bengal. Surface sediment samples were collected at 5 km intervals along the coast and at 5 m intervals from dune to low tide within each location, resulting in a total of 97 samples.

These samples were analyzed for grain size metrics, including mean, standard deviation, skewness, and kurtosis, using the R software package G2Sd. Granulometric and granule trends, along with heavy mineral analysis, were conducted to discern textural characteristics, sediment shape, and variations in mineral content. The study employed bivariate graphs, linear discriminant function analysis, C-M diagrams, and Tractive current plots to elucidate depositional environments and sediment transport dynamics. The results revealed significant temporal changes in sediment characteristics. Pre-tsunami sediments were finer, especially in high tide areas, while post-tsunami sediments showed a marked coarsening.

Recent sediments indicate a return to finer conditions, resembling pre-tsunami states, except in highly erosive areas like Poompuhar, Chandrapadi, and Nagoor. The study also noted shifts in sediment sources, with a decline in riverine and tidal sands and an increase in aeolian and marine deposits. Variations in heavy minerals, particularly the resurgence of certain placer deposits in recent years, highlight the complex interplay of geological processes shaping coastal evolution. This research provides critical insights for coastal management and disaster risk reduction.

Download

Share

COinS