In 2018, Kerala, an Indian state, experienced one of the worst floods in a century. Despite the fact that evacuation procedures were followed, the state’s Disaster Management Authority reported 433 fatalities as a result of the flooding. According to the state government, floods directly impacted one-sixth of the population. Alappuzha, Ernakulam, Idukki, Kottayam, Pathanamthitta, Thrissur, and Wayanad were the seven districts most severely affected.
During the southwest monsoon rainfall of 2018, the heaviest rains fell on June 14 and 20. Around July 20, there was another above-average amount of rainfall. A subsequent period of intense rain fell from August 8 to August 17. There was not enough buffer storage in the state’s dams to handle the massive influxes starting on August 8. Of all the districts, agricultural damage was greatest in Alappuzha (Source : State Government of Kerala, Additional Memorandum, 2018)
With the use of remotely sensed synthetic aperture radar (SAR) data and the computing abilities of Google Earth Engine, we examined a region close to the Alappuzha district (Figure 1). SAR technology has all-weather capabilities, making it useful for flood-prone area mapping. We employed Sentinel-1 SAR GRD imagery for this purpose. Two date images were prepared, one for the before-flood time period and the other for the after-flood time period. Subsequently, a composite image was prepared by using the above-mentioned two date images (Figure 2). The purple color indicated a huge difference in the situation before and after the flood event, which clearly was due to the flood water.
References:
Walia, A. and Nusrat, N. (2020). Kerala Floods 2018. National Institute of Disaster
Management, New Delhi, Pages 106.
