Flood Mapping Tutorial Using Sentinel-2 Data and QGIS

In this tutorial, we demonstrate a complete workflow for flood mapping using Sentinel-2 satellite imagery and QGIS, showing how freely available Earth observation data can be used to visually identify and quantitatively delineate flooded areas following a flood event.

The video begins with downloading Sentinel-2 data for a selected area of interest using the Copernicus Data Space Ecosystem web portal. After loading the data into QGIS, we inspect the Sentinel-2 dataset and explain its structure, including the different spectral bands and spatial resolutions. Understanding how Sentinel-2 imagery is organized is a critical first step before performing any flood analysis or spectral band combination.

Next, we create a false color composite using Sentinel-2 bands to perform an initial, visual-level flood extent identification. In this section, we explain how Sentinel-2 captures reflected solar energy across different wavelength ranges—not only within the visible portion of the electromagnetic spectrum, but also in the near-infrared region. By understanding how different surface materials such as water, vegetation, and built-up areas absorb and reflect energy at different wavelengths, we demonstrate how false color composites can be used to visually distinguish these land cover types and highlight potential flooded areas.

Building on this visual interpretation, we then introduce the Normalized Difference Water Index (NDWI) as a more systematic and quantitative approach to flood mapping. Using the green and near-infrared bands from Sentinel-2, we compute an NDWI raster that enhances surface water features while suppressing vegetation and other land surfaces. We explain the logic behind the NDWI formula, interpret NDWI values, and show how this index can be used to clearly map and extract flooded areas in a more objective and repeatable way compared to visual analysis alone.

Throughout the tutorial, QGIS is used as the primary GIS software for raster visualization, spectral band combinations, index calculation, and flood extent mapping. This video is suitable for beginners and intermediate users who want to learn Sentinel-2 flood mapping, understand the physical principles behind false color composites and NDWI, and apply these techniques in a practical GIS workflow.

Related Tutorials:
Downloading Sentinel 2 Satellite Data for Free - https://youtu.be/3EqSnqqt3Ds

Video Timestamps:
00:00 - Introduction
01:49 - Understanding Spectral Band Combinations
11:49 - Creating a False Color Composite Image
17:52 - NDWI (Normalized Difference Water Index)

Видео Flood Mapping Tutorial Using Sentinel-2 Data and QGIS канала GeoDelta Labs