Geomorphic processes in the vicinity of the Venkatapur River mouth, central west coast of India: implications for estuarine sedimentation

Abstract

We discuss geomorphic processes in the vicinity of river mouths of the central west coast of India using the Venkatapur River as a representative. Multidate satellite image analyses, wave-refraction patterns, time-series beach section studies, and sediment characteristics were used to understand the geomorphic processes operating in the region. Multidate image analyses indicated a significant readjustment of mouth configuration as well as shoal features; spit growth northward across the Venkatapur River and other rivers of the region, e.g., the Gangavali, the Sharavati; a shift of the river mouth northward; narrowing of the river mouths; and development of submerged bars across the river mouths, etc. The beaches to the north of the Venkatapur River mouth showed erosion (retreated landward), whereas the beaches on the southern side of the river mouth accreted (grew seaward/alongshore). In general, the beaches showed accretion during postmonsoon and premonsoon intervals, and erosion during monsoon. Sediments on the beach are medium to very fine grained (1.38–3.45 Ø) and moderately to poorly sorted (σ  =  0.3–0.81), suggesting low-energy conditions during deposition. During the premonsoon period, resuspension of sediments occurs, and these sediments move landward and into the estuary, especially during high tide. Wave-refraction pattern shows wave divergence in the mouth of the river and wave convergence away from the river on either side during the premonsoon (March to May) period, leading to a wave shadow area in front of the river mouth. These processes lead to sedimentation in the estuary and dynamic changes in the vicinity of the river mouth.