Reconstructing the catalogue for extreme wave events from the Gujarat coastline (Western India) and their implications to coastal settlers during the last 6000 years

Abstract

The shoreline of Gujarat in western coast of India has remained exposed to tsunamis and storm surges in past from distant to regional sources and processes. The catalogue of past tsunami and storm events whose geological signatures have been archived in the coastal records, often hints at frequency, magnitude and recurrence. In present work, we compile all possible signatures of palaeo-extreme wave events and attempt to assess the vulnerability to this rapidly developing shoreline. We report a total of six major extreme wave events, out of which atleast two have been identified to be associated with palaeotsunami deposits, whereas three are storm surge deposits and one is designated as a washover deposit. Archeological findings like the presence of thick walls around Dholavira (an ancient Harappan coastal trading centre) is also supportive of Harappan learning from the wrath of marine waves they would have faced. This study reports the wider time gap between the events, attributed to lack of preservation, difficulty in recognition, higher reworking or lack of detailed investigation ~ making the task of estimating recurrence a mammoth effort. The study shows that the shoreline of Gujarat has remained vulnerable to extreme wave events atleast during the last 6000 years, and have affected ancient settlers as well as modern anthropological activities.