Flood Monitoring Bulletin 20Th May 2016

IWMI-FLD-SL-2016.V3

Sri Lanka Flood Monitoring Bulletin 20th May 2016

Monitoring and Assessment of Flood Situation using Satellite Data and Unmanned Air Vehicle

Monitoring floods using TerraSAR-X satellite data around Colombo District Date of acquisition: 19th May 2016 Data Provider: TerraSAR-X (German Aerospace Centre)

Remarks: Both pre (5th Dec 2008) and post (19th May 2016) satellite images were merged to determine only the standing water.

Color in blue are the standing waters as of 19th May 2016 along with Kelani river covering the Colombo and Gamapha districts. Most of the lowland areas were inundated completed with standing water up to 6feet. Most of the houses along the river were inundated. Date of acquisition: 19th May 2016 Data Provider: TerraSAR-X (German Aerospace Centre)

Remarks: Both pre (5th Dec 2008) and post (19th May 2016) satellite images were merged to determine only the standing water.

Color in red are the standing waters as of 19th May 2016 along with Kelani river covering the Colombo and Gamapha districts. Most of the lowland areas were inundated completed with standing water up to 6feet. Most of the houses along the river were inundated. Date of acquisition: 19th May 2016 Data Provider: TerraSAR-X (German Aerospace Centre)

Remarks: Both pre (5th Dec 2008) and post (19th May 2016) satellite images were merged to determine only the standing water.

Color in red shaded are the standing waters as of 19th May 2016 along with Kelani river covering the Colombo and Gamapha districts. Most of the lowland areas were inundated completed with standing water up to 6feet. Most of the houses along the river were inundated. Monitoring flooded area using Drone The recent low pressure system in Indian Ocean caused heavy rainfall across Sri Lanka since around Hanwella town 14 May 2016 causing widespread flooding and landslide in as many as 19 districts. Kelani Ganga river basin covering parts of Colombo is one of the worst flood affected area due to exceptional rainfall 350mm within 3 days. In response to this situation, IWMI and Disaster Management Center (DMC)-Sri Lanka activated a charter to support rapid emergency response through satellite imageries from multiple space agencies consisting of JAXA, THEOS, IRSO, TerraSAR-X and RADARSAT- 2 as a part of International Disaster Charter (IDC). The flood affected area in Kelani river basin were identified from satellite images, circulated as flood bulletins (link to previous bulletin) and shared with the disaster and emergency response teams along with decision making authorities. The flood extent derived from satellite observations are being used by Emergency Operation Centre (EOC), DMC and SL Air Force to drop food and relief supplies.

While the satellite images provided an overview of large scale flood affected area, further local scale high resolution assessment are needed to concrete relief measure and damage assessment. Hanwella located approximately 30 km from Colombo were identified from satellite images for further damage assessment using high resolution Unmanned Aerial • Red box indicates drone survey carried out Vehicle (UAV). With the consent from SL airforce, SenseFly eBee UAV with 4 cm resolution, to determine flood damages; • Polygon in blue indicates standing water mapping using RGB sensor band was deployed at 70 m above ground level at 3.30 pm to during field investigation cover an approximate area of 100 ha along the banks of Kelani Ganga river near Hanwella. Mapping flood severity using Unmanned Air Vehicle or Drone in Hanwella town along the Kelani Ganga River

• Drone with 4 cm spatial resolution deployed at 70 m above ground level at 3.30 pm to map flood damages along the Kelani Ganga river near Hanwella. • Most damages noticed in the household than the crop damages • Several roads has been disconnected restricted the movement of population as well as rescue operations Location: Hanwella town along the Kelani Ganga river Location: Hanwella town along the Kelani Ganga river Flood Damage Assessment using Drone or UAV Location: Hokandara town near Colombo

• Left image (before flood) taken by Drone or Unmanned Air Vehicle on September 2015. The image clearly shows healthy crop condition • Right image (during flood) taken on 20th May 2016. The light or mud color indicators crop areas partially or fully submerged by floods. The release of water from the Kelani Ganga river. Flood Damage Assessment using Drone or UAV Location: Hokandara town near Colombo

• Standing flood water monitored using Drone in Hokandara town dated 20th May 2016 at 10:30am • Several houses has been damaged due to the excess water level in the Kelani Ganga and local rainfall leading to the standing water for more than 5days. Flood Damage Assessment using Drone or UAV Location: Hokandara town near Colombo

• Standing flood water monitored using Drone in Hokandara town dated 20th May 2016 at 10:30am • The image clearly shows submerged highways closer to E02 express line. • Several houses has been damaged due to the excess water level in the Kelani Ganga and local rainfall leading to the standing water for more than 5days.