Martinmbiro/machakos-flood-detection-2024

Using Sentinel-2 Imagery to detect and monitor floods in Machakos County, Kenya - 2024. Logic written in Python # Flood detection using Satellite Imagery Hello again 👋 + Last year, (2024) Kenya experienced heavy rainfall in the months of March, April and May that resulted in a humanitarian crisis (see photos here) + According to this UNOCHA report based on Kenya's National Disaster Operations Centre, more than 50,000 people in Machakos County were affected by the subsequent floods; of whom 29,000 were displaced from their homes. + In this repository, I demonstrate how remote sensing data would have been critical in detecting surface water and mapping the extent of floods over time. Such valuable insight would have aided responders to see the bigger picture quickly, pinpoint critical areas and make data driven decisions. ## Key terms 📝 Here's a few key concepts to note before proceeding: 1. **Sentinel-2** + A pair of European satellites (Sentinel-2A & 2B) that take **multispectral images of Earth** every 5 days at high resolution (10m - 60m) 2. **Multispectral image** + An image that has many **bands**, each recording light (or radiation) from a different part of the spectrum - eg. blue, green, red, near-infrared (NIR), shortwave infrared (SWIR), e.t.c + Each **band** "sees" the earth differently, and combining them helps detect things such as vegetation, soil, urban areas, or water - such as in this exercise 3. **Image band** + One layer of information in a multispectral image + Sentinel-2 images, for instance, have `13` bands, eg. `B3` - Green, `B4`- Red, `B8` - NIR, `B11`- SWIR1, e.t.c 4. **Modified Normalized Difference Water Index (MNDWI)** + A remote sensing index that uses the green band and the shortwave infrared (SWIR) band of a satellite's image **to highlight open water** features while suppressing noise from built-up land, soil, and vegetation + In the context of Sentinel-2: >> `MNDWI = (B3 - B11) / (B3 + B11)` + I'll be using `MNDWI` in this exercise 5. **Mask** + A mask is an image that tells Earth Engine which pixels to ignore / hide + For instance, a _cl …