Chennai floods map: Crowdsourcing data and crisis mapping for emergency response


The current rains in Chennai, India, have been termed as the heaviest in over 100 years, with huge floods as a result. For residents and responders, this means that reliable data on which streets are flooded, and which areas are inundated, is crucial in determining how to best react - but what if this data doesn't exist?

A rapid response project spearheaded by Arun Ganesh, Sanjay Bhangar, and Aruna S, has utilized OpenStreetMap to fill these data gaps. Individuals report areas that are flooded by zooming in on the map, and clicking on the relevant area. Once reported, flooded areas turn pink, allowing citizens and responders to plan accordingly.

"In the last 24 hours, over 2,500 streets have been reported as flooded by the citizens of Chennai using the tool. Although not individually verified, these contributions show patterns in the city and residential zones built around large waterbodies and wetlands that are vulnerable during the monsoon," writes Ganesh.


As well as the crowdsourced OpenStreetMap data, the project also leverages the following data:

  • UNITAR and UNOSAT satellite-detected inundated areas and probable flood waters, derived from comparisons of imagery collected on 12 November 2015, 01 September 2015, and 14 October 2015. Download the dataset here.
  • Geographic data representing low lying and flood prone areas from India's National Remote Sensing Centre's ISRO Cartodem3 and USGS' EarthExplorer.
  • Crowdsourced locations of relief centers. Download the dataset here.
  • Google maps data compiled by The Wire indicating waterlogged roads. Download the dataset here.

All of this collected data is also available for download as a geojson using an Ajax request on the project's GitHub page.

Explore the map here.