Where did the floodwater spread — even under clouds?
Analysis-ready products for actual events that this question maps to — open each in the catalog, or browse them on the NASA Disasters Portal.
Draw a rectangle to pick your area of interest, then see what NASA data covers it (live, here in your browser) or download a ready-to-run notebook with your AOI pre-filled. The notebook runs in any Python environment — it needs a free Earthdata Login to fetch the data.
-99.3, 29.9 → -98.9, 30.2 (Kerrville, Texas)During a flood the most urgent question is simply *where is the water* — and clouds usually hide it from optical satellites at exactly the moment you need them. This is the flagship case for radar.
During a flood the most urgent question is simply where is the water — and clouds usually hide it from optical satellites at exactly the moment you need them. This is the flagship case for radar.
What you can answer
- The flooded footprint, through cloud. Sentinel-1 SAR is a radar — it makes its own illumination and passes through clouds and darkness. Calm floodwater bounces the radar away from the sensor, so it appears dark; OPERA DSWx turns that into a ready-made water / no-water map.
- The newly flooded land — difference a pre-event and post-event water map to isolate water that wasn’t there before.
- What drove it — GPM IMERG gives the rainfall totals behind the event.
What you can NOT answer (easily)
- Water depth — extent ≠ depth; depth needs a terrain model (DEM) and assumptions.
- Flooding under dense canopy or in dense cities — buildings and trees scatter radar; fill those gaps with optical (Sentinel-2 SWIR) when skies clear.
- Minute-by-minute, everywhere — each satellite revisits only every few days.
How you’d approach it
Pull a pre-event and post-event DSWx (or threshold Sentinel-1 backscatter), difference them for the new-water mask, clip to your area, and overlay population and buildings to see who’s affected. The notebook below sets this up for your drawn AOI. This question supports the Respond phase of the NASA Disasters program.
Make it yours → Draw your AOI and set the pre-event and post-event dates, then overlay your own population or buildings layer to see who's affected.
The thresholding a measurement into classes at the heart of this question — runnable on synthetic data, right here. The full earthaccess code template further down does it on real NASA data (needs an Earthdata login).