Approximation of Flow Patterns for Submarine Channel Systems in the Arabian Sea using a GIS Approach

Abstract

The Indus fan in the Arabian Sea is the second largest submarine fan in the world after the Bengal fan. Despite being an extensive physiographic and sedimentary feature, detailed mapping of the channel systems is very limited. Identification of five unreported deep sea channels using multibeam swath bathymetry data (collected by NCAOR) led to the outset of this study. Based on this survey in conjunction with the global seafloor topography data, here we present a GIS approach to report a “Projected Channel System” (PCS). Identification of the PCS is dependent on the calculation of flow direction. The values of flow direction raster range from 1 to 128, where 1 represents east; 4 depicts south; 16 is west and north is shown as 64. Subsequent calculation of flow accumulation and ordering of streams helped in marking major and minor streams. The method has successfully captured channel systems belonging not just to Indus drainage basin but several others, in an area of 3.03 x 10⁶ km². Data from previously published channel systems – belonging to the Indus system were used to validate the results. Average offset distance between previously identified channels and PCS channels was ~10 km, indicating a reasonably good overlap.