Satellite detected water extents in Bolikhamzai Province, Lao PDR as of 18 September 2024

**UNOSAT code FL20230807LAO** This map illustrates cumulative satellite-detected surface waters over Khammouan & Savannakhet Provinces, Lao PDR as oberved from a Sentinel-1 image acquired on 04 August 2023 at 18:04 local time. Within the analysed area of about 25,000 km², a total of about 160 km² of lands appear to be flooded. Based on Worldpop population data and the detected surface waters in the analysed area, ~18,000 people are potentially exposed or living close to flooded areas. This is a preliminary analysis and has not yet been validated in the field. Please send ground feedback to the United Nations Satellite Centre (UNOSAT). Important note: Flood analysis from radar images may underestimate the presence of standing waters in built-up areas and densely vegetated areas due to backscaterring properties of the radar signal.

**UNOSAT code TC20220928LAO, GDACS Id: 1000922** This map illustrates satellite-detected surface waters in Khongxedone District, Saravan Province & Sanasomboon, Champasak Province, Lao PDR as observed from a Sentinel-1 image acquired on 1 October 2022 at 05:45 local time. Within the extent of this map of 600 km2, about 14 km2 of lands appear to be flooded. Based on Worldpop population data and the detected surface waters in the map extent, about 1,800 people are potentially exposed or living close to flooded areas. This is a preliminary analysis and has not yet been validated in the field. Please send ground feedback to United Nations Satellite Centre (UNOSAT). Important note: Flood analysis from radar images may underestimate the presence of standing waters in built-up areas and densely vegetated areas due to backscattering properties of the radar signal.

**UNOSAT code TC20220928LAO, GDACS Id: 1000922** This map illustrates satellite-detected surface waters in Sukhuma District, Champasak Province, Lao PDR as observed from a Sentinel-1 image acquired on 1 October 2022 at 05:45 local time. Within the extent of this map of 360 km2 , about 12 km2 of lands appear to be flooded. Based on Worldpop population data and the detected surface waters in the map extent, about 2,500 people are potentially exposed or living close to flooded areas. This is a preliminary analysis and has not yet been validated in the field. Please send ground feedback to United Nations Satellite Centre (UNOSAT). Important note: Flood analysis from radar images may underestimate the presence of standing waters in built-up areas and densely vegetated areas due to backscattering properties of the radar signal.

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 map illustrates the evolution of satellite-detected surface waters in Sanamxay district, Attapeu province, as observed from the Radarsat-2 radar image acquired on 24 July 2018 and compared with a Radsarsat-2 image acquired on 10 July 2018. As of 10 July 2018, flooded areas and saturated soils were already visible, due to the heavy rains that happened previously to the collapse of the dam. As well, the reservoir controlled by the dam was full of water. As of 24 July 2018, an additional surface of 5,826 ha of inundated areas were detected, representing an increase of the surface waters of 66%, due to the collapse of the dam. At this date, the reservoir that was controlled by the dam has decreased in its size. 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.

**UNOSAT code: FL20240913LAO** This map illustrates the floods detected using Sentinel-1 images acquired on 11 September 2024 at 06:07 local time. Within the analysed area of approximately 60 km², about 7 km² of land appears to be affected by floodwaters, including 6 km² of croplands. According to WorldPop spatial demographic data, an estimated 2,500 people are exposed to or living near the flooded areas. Please note that this is a preliminary analysis and has not been validated in the field. We welcome any ground feedback that can be provided to the United Nations Satellite Centre (UNOSAT). Important: Flood analysis based on radar images may underestimate the extent of standing water in built-up or densely vegetated areas due to the radar signal's backscattering properties.