Late Holocene morphodynamic evolution of Thamirabarani delta and Thoothukudi tombolo in South India: insights from integrated analysis of early cartographic documents and satellite images

Abstract

The age of discovery and exploration (fifteenth-sixteenth century CE) in Europe and later colonisation of newly explored territories by Portuguese, Spanish, Danish, French, Dutch, and British led to extensive mapping/charting of coastal regions around the globe for navigation, as well as for political and military purposes. These sea charts and coastal maps contain rich geomorphological details and offer unique geographical inputs for studying past geomorphic processes. By meticulously combining data from early sea charts, maps, historical textual records, and satellite images, the current study intends to illustrate their relevance in comprehending the long-term (from the past few centuries to a few thousand years) geomorphological processes. The study area includes the coast of the Thamirabarani delta and the Thoothukudi coast in southeast Tamil Nadu, which is known for its historically important ports, viz. Korkai and Kayal or Palayakayal. These places, were functional ports in the past, are now located a few kilometres inland. This study provides the following multifaceted outcomes: 1) offered a novel understanding of the morphodynamic evolution of the Thamirabarani delta and Thoothukudi tombolo; 2) revealed the value of early maps not only in tracing the geomorphic dynamics and dating the observed changes but also in developing a better understanding of the interpretation keys of remote sensing data; 3) provided an understanding of anthropogenic impressions on the landscape (street pattern or agricultural field pattern) driven by geomorphic changes; the identification of these patterns help validating the content of early maps. Integrated study of early cartographic documents (widely available in various archives and libraries around the world) has a high potential to advance the understanding of the morphodynamic evolution of various coastal landforms at a global scale.