Satellite detected water extents between 17 and 21 March 2023 over Southern Region, Malawi

✦ DISCOVERED BY ORIONAIUnited Nations Satellite Centre (UNOSAT)Imagery and land coverMalawi
Malawi

About this dataset

**UNOSAT code TC20230314MWI, GDACS Id: 1000961** This map illustrates cumulative satellite-detected surface waters in Southern Region, Malawi between 17 to 21 March 2023 as observed from: VIIRS imagery from 17 to 21 March 2023; Sentinel-1 imagery acquired on 17 Mar. 2023 and Sentinel-2 imagery acquired on 21 Mar. 2023. Within the analyzed area of about 30,000 km2, about 2,100 km2 of land appear to be flooded. Based on Worldpop population data and the detected surface waters in the analyzed area, ~280,000 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 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 the backscattering properties of the radar signal.

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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