An increase in the built-up area in the watershed is a preliminary measurable indicator to understand the effect of urban development on the hydrologic response of the watershed. In this paper, the land use/ land cover map of sub watershed of Periyar River processed from Indian Remote Sensing(IRS) satellite is created to understand the spatial distribution of built –up area and to detect the expansion of built up area in the peri-urban areas of Cochin, Kerala, India. The Satellite imagery of IRS –1C LISS – III dated 7th February 1995 and IRS –P6 LISS – III dated 13th February 2005 were imported in ERDAS Imagine to create LU/LC map using Maximum Likelihood Method of supervised classification. A total of ten classes broadly including forest, plantation, grassland, barren land and built-up were classified. The forest cover factor was computed in ArcGIS which is used as a parameter for runoff calculation to assess the contribution of land cover on runoff modelling. A 6% increase in built –up is detected comparing the LU/ LC map indicating that it is undergoing rapid development. The forest cover factor has a slight difference from 0.57 to 0.62indicating that barren and grassland are been primarily converted to built-up area. The LU/LC map can be used as a preliminary indicator of man-made induced impervious surface. The areal extent of satellite image provides a means for effective planning in future.