Coastal Response to Cyclone Biparjoy (2023) along the Kachchh Coast: Characterising Modern Analogue for Storm Deposit

ABSTRACT The west coast of India along the Arabian Sea is frequently affected by tropical cyclones that significantly modify coastal morphology and inflict considerable socioeconomic losses. Very Severe Cyclonic Storm (VSCS) Biparjoy (2023) struck the Kachchh and Saurashtra coasts of Gujarat, causing widespread geomorphic changes. This study integrates remote sensing, field observations, grain-size analysis, and environmental magnetism to investigate cyclone-induced coastal responses at Pingleshwar, Mandvi, and Dhrabudi along the southwestern Kachchh coast. Geomorphic mapping revealed severe erosion at Pingleshwar, where a 2-4 m high stabilised beach ridge extending over 800 m underwent partial to complete degradation. Satellite-derived indices showed a decline in NDVI (0.095-0.04), indicating vegetation loss and topsoil erosion, while elevated NDWI values reflect storm-surge overwash and waterlogging. Similar erosional signatures were observed at Mandvi, particularly near the Rukmavati River mouth. Although grain-size characteristics at Pingleshwar and Mandvi remained largely unchanged, magnetic susceptibility analyses recorded a marked reduction in frequency-dependent susceptibility (χfd%), indicating erosion of pedogenically altered surface sediments enriched in superparamagnetic minerals. In contrast, Dhrabudi displayed a depositional response, with poorer sorting and finer-skewed post-cyclonic sediments indicating accumulation of storm-transported material. Wrack lines and anthropogenic marine debris deposited above the intertidal zone further confirm storm-surge overwash and inland sediment transport. The integrated dataset demonstrates that combining geomorphic mapping, spectral indices, sedimentological characteristics, and environmental magnetic proxies provides a robust framework for assessing coastal responses to extreme cyclonic events, while emphasising the critical role of local geomorphology in controlling erosion and deposition patterns.