Satellite Detected Water Extent in the Sanamxay District, Attapeu Province, Lao PDR

This map illustrates the satellite-detected water extent in the district of Khamkeuth in Borikhamxay province, in the central-northern part of Lao People’s Democratic Republic after the tropical storm SONCA-17. The UNITAR-UNOSAT analysis used a Sentinel-1 satellite image acquired on the 11 August 2017 and detected several areas with potentially standing waters. In the district of Khamkeuth ~2,441 ha are likely flooded. Kindly note, the district of Khamkeuth has been partially analyzed due to the image does not cover the full district. This is a preliminary analysis and has not yet been validated in the field. Please send ground feedback to UNITAR-UNOSAT.

This map illustrates the satellite-detected water extent in the District of Khongxedone, Salavan Province, in the southwestern part of Lao People’s Democratic Republic after the tropical storm SONCA-17. The UNITAR-UNOSAT analysis used a Sentinel-1 satellite image acquired on the 30 July 2017 and detected several areas with potentially standing waters. In the district of Khongxedone ~2,921 ha are likely flooded mostly affecting the central part of the district along the “Xe Don” river. This is a preliminary analysis and has not yet been validated in the field. Please send ground feedback to UNITAR-UNOSAT.

This map illustrates the satellite-detected water extent in the Phonhong & Viengkham Districts, Vientiane Province, in the northwestern part of Lao People’s Democratic Republic after the tropical storm SONCA-17. The UNITAR-UNOSAT analysis used a Sentinel-1 satellite image acquired on the 1 August 2017 and detected several areas with potentially standing waters. In the district of Phonhong 2,045 ha are likely flooded and in the district of Viengkham 1,077 ha. This is a preliminary analysis and has not yet been validated in the field. Please send ground feedback to UNITAR-UNOSAT.

This map illustrates the satellite-detected surface waters extent in Sanamxay district, Attapeu province, as observed from the TerraSar-X and Tandem-X radar imagery acquired on 27 July 2018. Satellite detected water extent analysis was performed by Centro Internazionale In Monitoraggio Ambientale Research (CIMA) & Luxembourg Institute of Science and Technology (LIST). Within the analyzed area, a total of 7,405 ha were detected as inundated, four days after the collapse of the dam. Disclaimer: Flood extent maps are derived from high quality satellite data using a scientifically validated retrieval algorithm. No liability concerning the contents or the use thereof is assumed by the producer. The information has limitations due to the quality and resolution of the original data sources, as well as the uncertainties associated with the retrieval algorithm. Please be aware that the thematic accuracy might be lower in urban and forested areas due to inherent limitations of the SAR analysis technique. This is a preliminary analysis and has not yet been validated in the field. Please send ground feedback to UNITAR - UNOSAT.

This map illustrates the satellite-detected surface waters extent in Sanamxay district, Attapeu province, as observed from the Radarsat-2 radar image acquired on 24 July 2018. The previous day, the Xe-Namnoy dam collapsed, inducing flash floods along the Vang Ngao river and affecting several villages located 50 km downstream. Within the analysed area 14,692 ha of surface waters were detected after the heavy rains that happened on 22 July and as well the collapse of the dam. Several villages and surrounding agricultural fields seems to be inundated. The villages of Ban Hinlat, Ban Thaseangchan, Ban Mai and Ban Samong-tai seems to be the most affected ones. It is likely that flood waters have been systematically underestimated along highly vegetated areas, along the main riverbanks and within built-up urban areas because of the special characteristics of the used satellite data. This is a preliminary analysis and has not yet been validated in the field. Please send ground feedback to UNITAR - UNOSAT.

This analysis illustrates a time series analysis of the evolution of satellite-detected surface waters in Sanamxay district, Attapeu province, based on satellite data recorded on 13, 25 and 29 July 2018.