Radar imagery provides a convenient way to map inundated areas, because of it’s ability to penetrate cloud cover.
Below, try the application to check out inundated areas for some of the major floods of 2024, for example.
The default application centers on the town Malavalli in South India. Between July 30th and August 1st 2024, I was traveling by car near Malavalli in southern India. Google maps and IMD reported flood risk since the day before; however it was impossible to find any near-real time, useful information. Crossing the Kaveri river on the 30th, the river was wide and beautiful, maybe 20 ft below the long bridge. On August 1st driving back on the bridge, it was different. The river had overflowed its banks into adjacent fields, the river was less than 4 feet below the bridge. The next few days I wondered if the bridge had been overcome, if the water kept rising.
I started thinking of what satellite imagery I could use since satellite imagery has long been used to monitor flooded areas. However, optical imagery is limited by cloud cover and is not very useful in monsoon seasons (imho). Looking into radar imagery from the Sentinel-1 satellite mission, I found that there was a satellite pass on Aug 1 and played with it.
Here’s a simple application that indeed shows the river flooding out between July (left image) and August (right image) – the dark areas are water.
Radar penetrates clouds and is, generally, well suited for rapid assessments. I’m also using this to investigate applications for managed wetlands, and floods in other regions.