Meso-scale foreshore evolution in low-energy, storm-dominated tropical west coast of India: Implications for shoreline management

Along the tropical coast, there is cyclic variation in wind, wave currents, water and sediment influx, and the coasts experience a monsoonal storm surge that reaches nearly 2–3 times higher than the rest of the year, and foreshores undergo a complex evolution during an annual cycle. Hence, knowledge of foreshore evolution is critical in shoreline management. In this paper, study results on meso-scale foreshore evolution in a low-energy headland bay beach, situated in the Central West Coast of India near Manki, are discussed based on their seasonal and decadal changes in sandy shoreline configuration, wave refraction, sediment movement and depositional process. Decadal changes in the shoreline configuration indicated headland-side erosion and bay growth whereas the southern end grown seawards between the period 1979 and 2001–2002, while the beaches adjacent to the creek present in the area showed accretion and farther south of the creek showed minor erosion, and the trend continued through 2015. Wave refraction patterns for the waves approaching from northwest (NW), west and southwest (SW) for the wave periods 6, 8, 10 and 12 s indicated (a) wave convergence at the central part of the Manki beach; for the waves approaching from NW for wave periods 6 s; (b) wave divergence for the waves approaching from west with wave periods 6, 8, 10 and 12 s and (c) wave convergence at the bay side for the SW as well as NW approach of waves for wave period 10 s. Seasonal beach modification, in general, indicated post-monsoonal to pre-monsoonal (September to April) accretion and May to September erosion. Foreshore is gentle and dissipative (