Satellite-Detected Flood Extent in Nepal Provinces 1 and 2, July 2021

UNOSAT analysis FL20210630NPL maps surface water extent from Sentinel-1 radar imagery acquired on 1 July 2021. The analysis covers approximately 110,000 km², indicating about 645 km² of flooded land and an estimated 700,000 people potentially exposed. This is a preliminary, unvalidated analysis produced by the United Nations Satellite Centre (UNOSAT).

Use Cases

• Assess flood impact and extent based on satellite-detected surface water area.
• Estimate population exposure to flooding based on integrated WorldPop data.
• Validate or supplement field reports with preliminary geospatial analysis.
• Monitor changes in water bodies in built-up or vegetated areas using radar imagery.

Strengths

• Analysis covers a specific area of about 110,000 km².
• Provides quantified estimates: approximately 645 km² of flooded land and 700,000 people potentially exposed.
• Uses Sentinel-1 radar imagery analyzed with AI-based methods for automated water detection.

Limitations

• Preliminary analysis not validated in the field; accuracy may vary.
• Radar-based analysis may underestimate standing water in built-up and densely vegetated areas.
• Column-level documentation is absent; field semantics must be inferred after download.

Provenance

Source

United Nations Satellite Centre (UNOSAT)

Collection Method

Automated analysis of Sentinel-1 radar imagery using Artificial Intelligence based methods.

Time Range

Observation date: 1 July 2021.

Freshness

Last updated 2026-04 15 10:11:58.992874; freshness should be verified.

Geography

Province 1 and 2, Nepal.