Drainage Morphometry of Harangi Watershed, Madikeri District, Karnataka State and Its Influence on the Areas Sensitive to Soil Erosion

Watershed morphometry involves quantitative measurement and mathematical analysis of a drainage basin. Inference on the erosion of the landforms of the watershed area can be made based on the assessment of morphometric parameters. Toposheets in conjunction with the ASTER DEM were used for delineation of Harangi watershed and its subwatersheds in GIS environment as well for extraction of morphometric data. Relevant drainage morphometric parameters for the assessment of the sites for the vulnerability of erosion were evaluated using established mathematical expressions. The observed drainage patterns such as trellis, subparallel and subrectangular and alignment of the streams to the lineaments in the study area suggest an immense control of structure on the drainage pattern in Harangi watershed. The relief values, high values of ruggedness number and moderate values of dissection index suggest that the northern subwatersheds, which are characterised by steep slopes, witness low infiltration at higher reaches, high gravity flow and runoff. Low values of form factor, circularity (0.3) and elongation ratios (0.18) and high values of Gravelius’s compactness coefficient indicate that the majority of the subwatersheds are elongated in shape. The evaluated linear, areal and relief parameters in GIS environment indicate that the northern subwatersheds are in their late youth stage geomorphic development and are more prone to soil erosion as they are large in areas and consist of more number of streams and high relief compared to their southern counterparts.