Active channel systems in the West Basin,Andaman Fore Arc: results from high-resolution bathymetry surveys and GIS analysis

Using multibeam swath bathymetric survey, a moderate sinuosity meandering channel was identified in the West Basin which is extending up to the northwestern corner of the Alcock Rise. Detailed morphometric analysis indicates that this channel is a mature sinuous channel which acts as a major conduit for the sediments into the West Basin. The straight length of the channel is ～70 km with an axial length of ～85 km. Furthermore, the maximum width is 1.5 km and minimum width is 0.4 km with an average sinuosity value of ～1.16, indicating its moderate meandering nature. It is interesting to note that this channel lacks the physical connection with the continental slope of the Andaman and Nicobar Islands. From multibeam data, the channels seem to emerge from Andaman Island; by using GIS techniques, a derived channel network system is obtained to identify the source, which reveals that its exact source is the Irrawaddy Delta system. Furthermore, this study even suggests that the major contribution of modern sediments to the Andaman Fore Arc basin is from Irrawaddy Delta, and sediment supply from Andaman continental slope also played an important role.