Using GIS mapping for Urban Flood Management in Chennai

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Posted on November 5, 2009 - 16:30
Information on the Flood Risk Mapping Study, funded by the Water Resources wing of the Public Works Department, an initiative of the Tamil Nadu State Government

For a GIS zealot like me, this is breaking news on the Indian mapping front. Finally a GIS application for risk-mapping and management of floods in India!

The Flood Risk Mapping Study, funded by the Water Resources wing of the Public Works Department to a tune of Rs 2,17 crores, is an initiative of the Tamil Nadu State Government. It is supported by the Centre's Department of Science and Technology and Survey of India in the research component of the project. This one-year project is being handled by Anna University’s Institute of Remote Sensing (IRS), Chennai.

A first-ever contour map of Chennai city will be prepared to map the run-off pattern of water during the monsoon. This shall involve preparing a digital elevation model of the city using ALTM (Airborne Laser Terrain Mapper) technology, which involves aerial surveys (with requisite permissions from Army, Navy and Air Force) and terrain scanning with a highly accurate laser rangefinder from a flying helicopter. With the aerial mapping completed in March, once the digital elevation model is ready, it shall be processed into a contour map, expected to be ready by February, 2010.

The ALTM know-how, provided by German firm, Hansa Luftbild, has its first application in India with this Flood Risk Mapping Study project. High resolution images from American satellite 'Quick Bird,' would also be used in addition to the ALTM imagery.

The Institute plans to develop rain gauges to be installed in 30-35 of the most flood prone areas in Chennai. With rainfall, these would send signals to the control room, which would compute volume of water likely to be generated and send out warnings for mitigation and precautionary measures.

For a historically flat terrained Chennai, urban planning and disaster management has been a problem. An accurate contour map would enable ways and means of routing storm water and post-rain run-offs, paving the way for an effective stormwater drainage system and flood management. It is proposed that flood risk map sheets will be drawn up, ward-wise, covering the entire Chennai Metropolitan Area. With an accurate mapping of gradient, places suitable for artificial recharge of the ground water with the run-off, would also be computed. A hydrological simulation model simulating different flood situations and their possible management measures is also in the pipeline.

Covering a wider area than Chennai’s 174 sq. km., this project intends to map 500 sq. km. of greater Chennai. The mapping and the assessment of up-to-date land use will not only help planners fine tune projects but also recognise specific problems of monsoon flooding and clogged drains. 

Based on the success of the project, the model is proposed to be replicated in other metropolitan cities, repeatedly affected by rainwater flooding.

Interesting links for further reading:

http://www.fig.net/pub/accra/ppt/ts19/ts19_03_hadley_ppt.pdf

http://www.beg.utexas.edu/coastal/survey/altm.htm

Year: 
2009