River Profile Modeling and Fluvial Geomorphological Evaluation of Thoppaiyar Sub-Basin Using Geoinformatics Technology

The curvature of river profiles has long been taken to be a fundamental indicator of the underlying processes governing fluvial erosion and thereby of landscape evolution. Longitudinal profile is a graph of distance verses elevation is an x-y plot showing bed elevation as a function of downstream distance. Due to the plate movement is considerably slow, the human history record is too short to register landscape change for such a long time scale. In the present study, an attempt has been made the quantitative analysis of geomorphic indices coupled with some mathematical models for the Thoppaiyar sub-basin and its 16 micro-basins, including the gradient index (SL), normalized gradient index (SL/k), Profile complexity index (PCI) and slope-area relationship (Slr). Based on quantitative results of these geomorphology indices, this study suggests that the important factor influencing landscape of the Thoppaiyar sub-basin. Topographic map, IRS P6 LISS III satellite data, 10 m contour interval, SRTM data and ArcGIS 9.3 software were utilized. The contour lines of topographic maps of the main river and 14 micro basins are digitized as control points. Models of the longitudinal profiles using simple mathematical functions were made considering four functions for describing the form of longitudinal profiles. The abnormally high SL and SL/k values indicated that a decreasing trend from lower to mid-stream areas and the result of slope–area relationship also indicated that the regression line of the upper and lower steam exhibit an obvious right-shift could be explained by geodynamic models of active deformation in Thoppaiyar sub-basin.