Quantitative Morphometric analysis of Kosasthalaiyar sub basin (Chennai basin) using remote sensing (SRTM) data and GIS techniques

The growing competition demand for water from industrial, domestic, and environmental sectors, along with increasing intensity of quality and quantity challenges as a result of rapid urbanization, call for scientific approaches to water resource management. Drainage basins, catchments and sub catchments are the hydrological units ideally suited for planning purposes focused on conserving land and water resources. The availability of remote sensing data and enabling GIS platform lend scope for understanding the morphometric properties of the catchment area and surface drainage characteristics of many river basins in different parts of the globe. Kosasthalaiyar sub basin with an area of 2835.06 km² playing a vital role for the water supply, food security and economic development of Chennai city was taken up for the study. SRTM data and Arc GIS 10, spatial analyst tools along with arc hydro tools were used for morphometric analysis of the sub basin to derive linear, relief, and aerial aspects. Strahler stream ordering techniques and analysis were followed for further analysis. The results revealed that the elongated sub basin is reasonably homogeneous in geology without structural disturbances with low relief and moderate to gentle slope in all the constituent sub-watersheds. The low drainage density is because of the highly permeable subsoil, with good permeability of sub-surface material and dense vegetative cover with low relief. The overland flow is significantly affected by infiltration and percolation through the soil, both varying in time and space. The analysis output leads to the conclusion that structural interventions are needed to improve the surface storage and landuse modifications for better water management.