The Chennai River Basins 30m SRTM Digital Elevation Model (DEM).
The 2015 floods of Chennai has significantly increased the interest of GIS professional to determine the flow path, vulnerable zone and mapping of potential flooding zones.
If you are a GIS professional, you would start by using the Digital Elevation Model(DEM) for Chennai. This file is Shuttle Radar Topography Mission (SRTM) 30m resolution data. If you pay, higher resolution data products are available from various remote sensing agencies.
Shuttle Radar Topography Mission (SRTM) 1 Arc-Second Global (30m resolution) accessed via USGS Earth Explorer
Specifications can be viewed here: https://lta.cr.usgs.gov/SRTM1Arc