Shorelines experience significant changes near a coastal structure and around the confluence of a river and the sea. Field investigation and site data collection by the latest technologies for the detailed data collection would pave the way for the interpretation of the morphological changes close to the real scenario, which is essential for an efficient and sustainable coastal protection planning and coastal zone management. This paper deals with shoreline on either side of the mouth of the Arasalar River draining into the Bay of Bengal with a year-long (March 2018 to February 2019) continuous shoreline assessment during which GAJA cyclone made its landfall on 16 November 2018 along the Karaikal coast of Union Territory of Puducherry located on the southeast coast of India. A pair of training walls effectively keeps the mouth from silting, thereby allowing free passage of vessels. This study aims to understand the seasonal variation coupled with the severe cyclonic impact on the southeast coast of India. Monthly spring shoreline and cross-shore profiles during low tide and high tide were collected, including post-cyclone field data. The results discuss the erosion and accretion pattern of the sediment processes adjacent to the training walls and cyclone effects. © 2020, © 2020 Indian Society for Hydraulics.