Satellite detected water extents between 2nd Aug. & 5th of Sep. 2021 in Dosso, Niamey and Tillaberi regions of Niger

✦ DISCOVERED BY ORIONAIUnited Nations Satellite Centre (UNOSAT)WaterNigerSource offline
Niger

About this dataset

**UNOSAT code: FL20210908NER** This map illustrates the extent of surface waters (cumulative) in Dosso, Niamey, Tahoua and Tillaberi regions of Niger as detected by VIIRS-NOAA satellite between the 2nd of August & the 5th of September 2021. Within the analyzed cloud free zones of about 260,000 km2, a total of about 900 km2 of lands appear to be flooded. Based on Worldpop population data and the detected surface waters, about 120,000 people are potentially exposed or living close to flooded areas. The potentially exposed population is mainly located in the region of Dosso with ~40,000 people, Tillabéri with ~40,000 people and Tahoua with ~22,200 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).

Documentation

UNOSAT datasets and maps are produced using a variety of methods. In general, analysts closely review satellite imagery, often comparing two or more images together, and determine notable changes between the images. For damage assessments, refugee or IDP assessments, and similar analyses, these changes are then manually documented in the vector data by the analyst. For flood extractions, landcover mapping and similar analyses, a variety of automated remote sensing techniques are used to extract the relevant information which is then reviewed and revised as necessary by the analyst. In all cases, resulting data is then loaded into a standardized UNOSAT geodatabase and exported asshapefiles for dissemination. This is a preliminary assessment and has not yet been validated in the field. It is important to consider the characteristics of the source imagery used in the analyses when interpreting results. For damage assessments it should be noted that only significant damage to the structural integrity of the buildings analyzed can be seen in imagery, while minor damage such as cracks or holes may not be visible at all. For flood extractions using radar data it is important to note that urban areas and highly vegetated areas may mask the flood signature and result in underestimation of flood waters. Users with specific questions or concerns should contact unosat@unitar.org to seek clarification.

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Satellite detected water extents between 3 & 7 of September 2021 in Dosso, Niamey, Tahoua and Tillaberi regions of Niger

**UNOSAT code: FL20210908NER** This map illustrates the extent of surface waters (cumulative) in Dosso, Niamey, Tahoua and Tillaberi regions of Niger as detected by VIIRS-NOAA satellite between the 3rd & the 7th of September 2021. Within the analyzed cloud free zones of about 230,000 km2, a total of about 310 km2 of lands appear to be flooded. Based on Worldpop population data and the detected surface waters, about 45,000 people are potentially exposed or living close to flooded areas. The potentially exposed population is mainly located in the region of Dosso with ~26,700 people, Tillabéri with ~10,900 people and Tahoua with ~6,600 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).

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Satellite detected water extent in Tillabéri & Niamey Regions, Niger as of 05 October 2022

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Satellite detected water extent in Tillabéri Region, Niger as of 19 August 2022

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**UNOSAT code: FL20240902NGA, GDACS ID: 1102720** This map illustrates cumulative satellite-detected water using VIIRS in Nigeria between 5 to 9 September 2024. Within the cloud free analyzed areas of about 815,000 km², a total of about 14,000 km² of lands appear to be affected with flood waters. Based on Worldpop population data and the maximum flood water extent, about 2,650,000 people are potentially exposed or living close to flooded areas. The pixelwise water fraction from VIIRS, using a 5-day composite at 375 m spatial resolution, indicates potential floodwater coverage ranging from 0% to 100%. This large-scale analysis is intended for guidance purposes and has not yet been validated with ground truth data or higher-resolution analysis. The population exposure analysis is based on floodwaters observed only in cloud-free areas, so the total number of people exposed may be underestimated. 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).

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