Preliminary satellite-derived flood assessment in Lower Northeastern Part of Thailand as of 11 November 2021

**UNOSAT code: FL20210928THA** Summary Of Findings; Floodwaters observed in 17 provinces as of 2 November 2021; Receding flood waters observed in Central Region as of 2 November 2021; Standing flood waters observed in Sukhothai, Phitsanulok, Kamphaeng Phet, Phichit, Phetchabun, Nakhon Sawan, Uthai Thani, and Kanchanaburi provinces as of 2 November 2021;  Increased standing flood waters observed in Chai Nat, Suphan Buri, Sing Buri, Ang Thong, Saraburi, Lop Buri, Ayutthaya, Nakhon Pathom and Pathum Thani provinces as of 2 November 2021.

**UNOSAT code: FL20210928THA** This map illustrates satellite-detected surface waters in Northeastern part of Thailand as observed from a Sentinel-1 image acquired on 10 Oct 2021 at 06:00 local time and using an automated analysis with Machine learning method. Within the analyzed area of about 60,000 km2 , about 660 km2 of lands appear to be flooded. The water extent appears to have decreased of about 100 km2 since 5 October 2021 and moved toward east part. Based on Worldpop population data and the detected surface waters in the analyzed area, the potentially exposed population is mainly located in the district of Mueang Khon Kaen with ~ 6,300, Kosum Phisai with ~ 6,000 people, and Phimai with ~ 5,300 people. 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: FL20210928THA** This map illustrates satellite-detected surface waters in Khon Kaen, Chaiyaphum, Nakhon Ratchasima, and Nong Bua Lam Phu provinces, Thailand as observed from a Sentinel-1 image acquired on 5 Oct 2021 at 18:20 local time and using an automated analysis with Machine learning method. Within the analyzed area of about 40,500 km2 , about 770 km2 of lands appear to be flooded. The water extent appears to have decreased of about 70 km2 since 29 September 2021. Based on Worldpop population data and the detected surface waters in the analyzed area, the potentially exposed population is mainly located in the district of Phimai with ~ 10,400 people, Non Sung with ~ 9,000 people, Mueang Chaiyaphum with ~ 6,700 people, Mueang Khon Kaen with ~ 4,500 people, and Chonnabot Thai with ~ 4,300 people. 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 the southern provinces of kien Giang, An Giang, Dong Thap & Can tho as observed from the Sentinel-1 SAR images acquired on 16 & 28 August 2018. In the analysed area, an increase of surface waters is observed mainly in agricultural and paddy fields areas. It is likely that flood waters have been systematically underestimated along highly vegetated areas along main river banks and within built-up urban areas because of the special characteristics of the satellite data used. This is a preliminary analysis and has not yet been validated in the field. Please send ground feedback to UNITAR - UNOSAT.

**UNOSAT code: FL20210928THA** This map illustrates satellite-detected surface waters in Northeastern part of Thailand as observed from a Sentinel-1 image acquired on 17 Oct 2021 at 18:20 local time and using an automated analysis with Machine learning method. Within the analyzed area of about 60,000 km2 , about 810 km2 of lands appear to be flooded. The water extent appears to have increased of about 220 km2 since 16 October 2021. Based on Worldpop population data and the detected surface waters in the analyzed area, the potentially exposed population is 80,000 people mainly located in province of Khon Kaen Province with ~ 24,000 and Nakhon Ratchasima with ~ 22,000 people. 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 TC20220928THA, GDACS Id: 1000922** This map illustrates satellite-detected surface waters in Ubon Ratchathani Province, Thailand as observed from a GeoEye-1 image acquired on 20 October 2022 at 10:35 local time. Within the analysis extent of this map, about 120 km² of lands appear to be flooded. Based on Worldpop population data and the detected surface waters within the analysis extent, approximately 32,000 people are potentially exposed to or living close to flooded areas along with 11,330 structures and approximately 400 km roads potentially damaged by flooding. This is a preliminary analysis and has not yet been validated in the field. Please send ground feedback to United Nations Satellite Centre (UNOSAT).