A Flood of the Century in India

Abnormally heavy monsoon rains drenched Southeast Asia, leading to the worst flooding in the state of Kerala since 1924. The event, which started with rains on August 8, 2018, displaced over 300,000 people, led to hundreds of deaths, damaged over 50,000 houses throughout the region, and severely affected 13 of the 14 districts in Kerala. While it brought the region’s most intense flooding this summer, the rain was one of many high precipitation events in Kerala this monsoon season.

The image shows satellite-based rainfall accumulation from July 19 to August 18, 2018. Rainfall peaked in Kerala on July 20 and again reached abnormally high levels between August 8 and 16. Since the beginning of June, the region received 42 percent more rainfall than normal for this time period. In the first 20 days of August, the region experienced 164 percent more rain than normal.

Kerala’s August rain played a part in the nearly once-in-a-century flooding, although the flooding was worsened when water was released from several full dams. Instead of gradually releasing water during drier times, authorities were forced to open 80 dams in the region, including the Idukki Dam, which is one of the largest arch dams in Asia. Thirty-five of those dams were opened for the first time.

“The dam releases came way too late, and it coincided with the heavy rain that was occurring,” said Sujay Kumar, research scientist at NASA’s Goddard Space Flight Center

Intense rainfall events have hit other areas of Southeast Asia as well. Eastern Myanmar experienced torrential downpours in mid-July and August, causing fatalities and displacing 150,000 people in one month. The floods were the worst in 30 years. The Bago and Sittaung rivers swelled to their highest levels in more than five decades, with the Sittaung river 7 feet above danger levels in areas.

These rainfall data are remotely-sensed estimates that come from the Integrated Multi-Satellite Retrievals (IMERG), a product of the Global Precipitation Measurement (GPM) mission. The GPM satellite is the core of a rainfall observatory that includes measurements from NASA, the Japan Aerospace Exploration Agency, and five other national and international partners. Local rainfall amounts can be significantly higher when measured from the ground.


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