> For the complete documentation index, see [llms.txt](https://mapbox.gitbook.io/open-data-openstreetmap/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://mapbox.gitbook.io/open-data-openstreetmap/case-studies/chennai-immediate-value-of-crowdsourced-data-collection.md).

# Chennai - Immediate value of crowdsourced data collection

#### The [Chennai floodmap](https://www.mapbox.com/blog/chennai-flood-map/) was instrumental in allowing Chennai's residents to take disaster response into their own hands

Mapbox Bangalore created a crowdsourced visualization of Chennai’s flooded streets after the strongest monsoon rains of the century hit and disrupted the life of over 6.7 million people. No up-to-date map of flooded streets as a measure of the devastation was available to residents and local media. The easy-to-use digital tool built on top of OpenStreetMap lets users zoom in, discover which streets are reported as flooded (pink), or click on a street that they know is flooded to report it.

## Stakeholders involved

* Mapbox Team reacting to the escalating situation using the tools they’re familiar with
* Local Media - frustrated with insufficient data provided by local government, such as an excel sheet with addresses of flood relief centers
* Government - unprepared to handle the escalating situation
* People of Chennai - ease of use, albeit not accessible for all groups of the community

## Types of data handled

* OpenStreetMap data - ODbL
* Topographic elevation data- Inundated areas (Nov 28) [Flood Waters Over Chennai Area UNITAR - UNOSAT](http://www.unitar.org/unosat/node/44/2312) (USGS)
* Inundated areas (Dec 3) ISRO RISAT 1
* Low lying locations: [ISRO Cartodem3](http://bhuvan.nrsc.gov.in/data/download/index.php) and [SRTM 30m](http://earthexplorer.usgs.gov/)
* Crowdsourced data

## Technical solutions

* Map to highlight low altitude areas of Chennai prone to flooding
* Functionality to mark road segments as flooded via browser without login using Mapbox GL JS and Datasets API. Mapbox GL JS allows to select individual features on the front-end, and selected roads are posted to a Dataset backed via the Datasets API.

### Subsequent outcome

* Map was picked up by an humanitarian organization working with the city for relief operations
  * Within 24 hours after major media outlets picked up word about the map, over 2,500 streets were reported to be flooded by the citizens of Chennai
  * Map available as [open source tool on Github](https://github.com/osm-in/flood-map)

![](https://1365483811-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-LSYocQ_W_6SRiGRDPxc%2F-LSYog9i1yQBhezJcwad%2F-LSYohBGLk01xupitDgs%2F44197744-984e-11e5-8ab5-ce53efbeae54.png?generation=1543568021341083\&alt=media)

## Further reading

* [gadgetsnow.com](http://www.gadgetsnow.com/apps/Bangalore-techies-build-app-to-help-Chennai-flood-victims/articleshow/50039041.cms)
* [thehindu.com](http://www.thehindu.com/news/cities/chennai/crowdsourced-map-to-mark-inundated-areas/article7935008.ece)
* [open source repo on Github](https://github.com/osm-in/flood-map/)