Sri Lanka

Sri Lanka: Mapping Flood Extent for Colombo and Gampaha and its surrounding using RADARSAT -2 Satellite imagery (23 May 2016)

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The recent low pressure system in Indian Ocean caused heavy rainfall across Sri Lanka since 14 May 2016 causing widespread flooding and landslide in as many as 19 districts, including around Colombo. Kelani Ganga is one of the main river basin in Sri Lanka which is currently experiencing large scale flooding and subsequent damage to property and livelihoods. Kelani basin received 350 mm of total rainfall within three days (15 to 17 May 2016). Regular monitoring of flood situation in North and Northwestern provinces with the support of International Disaster Charter and Sentinel Asia, allows rapid assessment of flood extent on a daily basis. The current flood images is from Canadian Space Agency RADARSAT -2 images for 21 May 2016 (6.25m spatial resolution) to estimate flooded areas progressing and declining. The information is being provided to Disaster Management Centre for relief and damage assessment.

The flood water has receded considerably in Kelani Ganga river compare to the report on 18th May 2016. As of today (21 May), the estimated inundated area is approximately for Kelani Ganga but other river basins are also affected including Deduru Oya ( as the higher inundation followed by Attanagalu Oya ( and Maha Oya and Karambalan Oya average inundation about In total the region of interest covering the basin is approximately covering 12 river basins. As mentioned earlier, most of this standing water are noticed in abandoned croplands, banana cultivations and large scale devastation in household area as well as several roads have been disconnected restricting the movement of general population. Six to ten feet of flood waters were observed in some household localities causing untold damage to rural households and gardens/croplands. Area under banana cultivation and rubber plantations are also currently under standing water. The flood affected Grama Niladhari (GN) divisions includes: Kolonnawa GND - Wellampitiya, Kelanimulla, Gotatuwa, Udumulla North, and Kaduwela_GND - Walpola , Kaduwela, Mahadeniya, Rangala, Welivita, Malabe West, Pahala Bomiriya, lhala Bomiriya) and for the Gampaha GN divisions- Gampaha, Biyagama, Dompe, Jaela, Diulapitiya based on the reports from DMC.

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