Morphometric Analysis and Micro-watershed Prioritization of Peruvanthanam Sub-watershed, the Manimala River Basin, Kerala, South India

Morphometric analysis is important in any hydrological investigation and it is inevitable in development and management of drainage basin. A critical evaluation and assessment of morphometric parameters and prioritization of micro-watersheds based on water holding capacity of Peruvanthanam sub-watershed have been achieved through measurement of linear, aerial and relief aspects of basins by using remote sensing and GIS techniques, and it necessitates preparation of a detailed drainage map. For prioritization, 9 micro-watersheds are delineated and parameters such as Rb, Dd, Fs,T, Lof and C are calculated separately and prioritization has been done by using the Raster calculator option of Spatial analyst. The analysis reveals that the stream order varies from 1 to 6 and the total number of stream segments of all orders counted as 347, out of which the maximum area (69.16%) is covered by 1st order streams and the minimum (0.29%) by 6th order. Lower values of Rb (linear parameters) in each order, higher values of Bh (0.90), Rh (0.07) and Rn (3.02) (relief parameters), high values of Dd (3.36), Fs (6.15), T (6.82), low values of Lof (0.14) and C (0.30) (aerial parameters) all together reveal that the sub-watershed has a complex structure, mountainous relief, high runoff and low infiltration. The maximum area is covered by high to medium prioritized zones (19.07km2) followed by low to very low (17.75km2) while a very high to high zone is only 4.72km2.