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flood maps guide emergency response in south asia

  • IWMI, in partnership with Sentinel Asia, activated its emergency response disaster charter twice during 2015. Led by the Asia-Pacific Regional Space Agency Forum (APRSAF), Sentinel Asia is an initiative through which organizations in the region use remote sensing (RS) and web-geographic information system (GIS) technologies to assist with disaster management. IWMI, which is a member of the Sentinel Asia Joint Project Team, provided flood mapping in October to its host Sri Lanka when exceptional rainfall inundated the Southern Province. Three months later, IWMI experts helped to prepare emergency response maps to aid relief and rescue operations in Chennai, India, following widespread flooding of the city and surrounding areas.

Continuous heavy rainfall from mid-September in the southern parts of Sri Lanka resulted in floods and landslides that caused eight deaths and injured nine people. In total, 7,300 people across four districts were affected by the adverse weather, and more than 600 properties were damaged. IWMI responded to a request for assistance from the Sri Lankan Disaster Management Centre (DMC), within the Ministry of Disaster Management (MoDM). For the first time, the Institute worked in collaboration with MoDM and the United Nations Platform for Space-based Information for Disaster Management and Emergency Response (UN-SPIDER) to prepare maps of the affected areas.


The maps showed the flooding situation in real time, using cloud-free satellite images provided by the Japan Aerospace Exploration Agency (JAXA). The accumulated rainfall was calculated to be around two to three times higher than that during the same period in 2014. The Relief and Emergency Unit of DMC used the maps to make rapid impact assessments and to guide their response to the disaster. This information was shared with other relevant authorities to aid their decision making. IWMI staff later accompanied DMC on a field mission to the affected districts to evaluate the scale of the flooding and assess its impact on paddy fields. This information was used to develop a situation report.

In Chennai, 30,000 people were evacuated after flooding left them stranded. Homes and public buildings were inundated and roads were made impassable. During November, IWMI provided flood situation maps using Sentinel-1 satellite data from the European Space Agency (ESA). As the situation escalated, IWMI produced emergency response maps using Advanced Land Observing Satellite-2 (ALOS-2) and Phased Array type L-band Synthetic Aperture Radar-2 (PALSAR-2) in collaboration with JAXA and in association with the Indian Space Research Organisation (ISRO). The maps were made available to the Chief Secretary, Government of Tamil Nadu, India’s National Disaster Response Force (NDRF), and international agencies, including the United Nations Office for the Coordination of Humanitarian Affairs (UN-OCHA), Reliefweb and UN-SPIDER.


IWMI is now developing a new drought monitoring system, which is based on similar technology. Early trials of the system in India indicate that it has the potential to detect emerging droughts before water shortages become critical.