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Sri Lanka

Sri Lanka: Mapping Flood Extent for Kelani Ganga River Basin and its surrounding using RISAT-1 Satellite imagery (19 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 wide spread flooding and land slid e in as m any 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 d am age to property and livelihoods. Kelani basin received 350 m m of total rainfall within three days (15 to 17 May 2016). The water levels of Kelani at Hanwella Gauge was 10 ft yesterday but receded to today 9 ft. Most of the runoff contributions are from rainfall in the upstream hilly area of Sri Pada mountain range.

IWMI received satellite imagery from RISAT-1 d ate d 18 May 2016 through International Disaster Charter (IDC) provide by Indian Space Researc h Organization (ISRO). It is estimated that the maxim um inundation ob serve d for 18 May 2016 is approximately 2,343 sq . km . As mentioned earlier, most of this standing water are notice d in abandoned croplands, banana cultivations and large scale devastation in house hold are a as we ll as several road s have been disconnected restricting the movement of general population.

The current flooding event affected 172,000 people in and around Colombo, 122,000 in Gampha and 12,757 in Kegalle mainly from land slide reported on 18 May 2016. Six to ten feet of flood waters we re observe d in some house hold localities causing untold d am age to rural house hold s and gardens/croplands. Are a under banana cultivation and rub b e r plantations are also currently under standing water. The flood affected Grama Niladhari (GN) divisions includes: Kolonnawa GND - Wellampitiya, Kelanimulla, Gotatuwa, Udumulla North, and Kaduwela_GN D – Walpola, Kaduwela, Mahadeniya, Rangala, Welivita, Malabe West, Pahala Bomiriya, Ihala Bomiriya) and for the Gampaha GN divisions - Gampaha, Biyagama, Dompe , Jaela, Diulapitiya based on the reports from Disaster Management Center (DMC).