Multidecadal Morphodynamic evolution of shorelines and coral reefs along the Arabian Sea Coast of Oman: Bar Al Hikman Peninsula

This study examines the morphodynamic evolution of the shoreline and coral reef coverage along the Arabian Sea coast of Oman over the past five decades (1972–2022). The Peninsula of Bar Al Hikman, the largest low-lying coastal area in Oman (550 km²; elevations < 10 m), hosts unique, monospecific coral reefs developing under a monsoon climate. Unlike other densely populated, low-lying coastal areas in the Middle East (e.g., the Gulf), the southern Arabian Plate has received limited attention, with few studies addressing its coastal evolution or future environmental risks. By combining sedimentological fieldwork with photo-interpretations of satellite images spanning 50 years, this study documents significant coastal geomorphological changes. The findings reveal a dramatic 60% reduction in the surface area of Bar Al Hikman’s main coral reefs. A significant consequence of this reef shrinkage is the rapid shoreline erosion on the leeward side of the disappearing reefs. Half of the southern shoreline of the peninsula is retreating northward at rates exceeding 1 m/year, with localized section (6%) eroding at extreme rates of over 10 m/year. At this pace, the ongoing reef decline is likely to exacerbate shoreline erosion, accelerate the landward migration of barrier bars and in turn close off lagoonal areas, and threaten intertidal ecosystems. Furthermore, with the ongoing global rise in sea level, a substantial portion of the peninsula is predicted to fall below the annual flood limit by 2050. This will result in the extensive landward migration of coastal sabkhas deeper into the peninsula's interior. Overall, this study provides a baseline for understanding the recent evolution of Oman’s Arabian Sea coastline and underscores the importance of developing policies and coastal management strategies to mitigate the effects of ongoing environmental and sea-level changes.