Flood Detection in Malawi Before and After Cyclone Idai by
Multi-temporal Sentinel-1 SAR Imagery
Abstract
Tropical cyclone (TC) Idai landing twice in March 2019 had made great
losses to Malawi and surrounding countries. Before the TC Idai landed,
Malawi had already experienced heavy rainfall since January. In order to
observe this disaster situation, 17 images of Sentinel-1 Synthetic
Aperture Radar (SAR) from 13 January 2019 to 19 April 2019 are used here
to estimate the flooding extent based on change detection. Results show
that the flooding area varied from 315 to 622 km2, arable land suffered
most, and for the percentage of flooding area the urban area suffered
most. This demonstrates obviously that the TC Idai may cause great
agricultural losses and make many people homeless. For flood detection,
SAR has shown much more powerful that optical sensors for its ability of
all-weather and all-day.