Littoral processes and their relevance to the submergence of ancient ports along Andhra coast, India

Abstract

The study of environmental parameters along the coast of Andhra Pradesh, India reveals that the area during December to March experiences mild waves (H sub(alpha) approx 1 m, T sub(alpha) approx 6 sec) predominantly from NE. Modification of wave parameters takes place in April and high waves (H sub(alpha) greater than 2m, T sub(alpha) greater than 8 sec., dir, 180-270) prevail during May-September. Qualitative picture of littoral currents also vary with the changes in the prevalent wave parameters. These currents were from NE for the waves from 90 degrees and from SW for 120 degrees wave approaches. Rio currents were also observed in these patterns. The observed currents were from NE (intensity 0-40 cm sec) in February whereas they were from SW (magnitude 20-70 cm sec sup(-1)) in September. Based on sediment budget between February 1981 to September 1982, it is found that about 117 m sediment deposits in a storm to swell cycle. The average rate of sediment deposition was 58 to 65 m for swell to storm profile transformation. The bivariant plots of size measures suggest that the source of the sediments is through river source. The dominance of depositional processes leading to the accretionary nature of the coast and their relationship with the submergence of ancient harbours in this region is discussed.