Geomorphometric comparison of submarine channel-levee complexes with fluvial river systems: observations from the Indus

Abstract

An analogy between submarine channels and fluvial rivers has existed for long, especially on the basis of planform and morphometry. Underlying this broad resemblance are the minute disparities that shape and control these systems. In order to observe and quantify the variations between submarine channels and subaerial rivers, we present a first-ever geomorphometric investigation of one single system, where the fluvial river is compared with its offshore counterpart from source-to-sink. With exhaustive data from the submarine fan, parameters like longitudinal profile, width, sinuosity, slope and planform of the Indus Fan channel-levee complex (CLC) are estimated and compared on the basis of the same parameters estimated for the fluvial Indus River. Our new data analyses offers key insights into the variable geomorphometric patterns prevalent from the source of the Indus River until the margins of the submarine Indus Fan. Channel width and sinuosity vary from high-to-low downstream in the submarine system and from low to high in the fluvial basin. Characteristic depositional features of either system are mutually exclusive. Longitudinal profiles of the submarine fan and the river basin do not conform—principally due to the difference in intensity of erosional and depositional processes active in both regions. These differences are primarily attributed to a single-point (canyon-fed) distributary flow and a multi-point (tributary-fed) cumulative flow source system, and density contrasts between river flows and turbidity currents. By quantifying this variation, our attempt is to dissuade the long-standing morphometric analogy between fluvial rivers and submarine channels.