From December 2016 and continuing until May 2017, much of western and central South America was plagued by persistent heavy rain events. In Peru, one of the most severely impacted nations, it has been referred to as the 2017 Coastal Niño. The flooding was preceded by drought-like conditions throughout the region for much of 2016 and a strong warming of sea temperatures off the coast of Peru.
Background
From 2014 to 2016, the Pacific Ocean experienced a significant El Niño event. By June 2016, the El Niño had subsided but lingering drought-like conditions persisted through the southern spring in late 2016. Starting in November 2016, a localized anomalous warming of the Pacific occurred which is known locally as the Coastal Niño. A Coastal Niño is differentiated from an El Niño event in that the Coastal Niño is localized to the coasts of Ecuador and Peru and does not expand into the equatorial central Pacific Ocean or impact global temperatures. This ocean warming contributed to unseasonably high rainfall in the region and, by January 2017, Peruvian officials had declared the warming a Coastal Niño occurrence.
Impacts
Colombia
On December 1, 2016, heavy rains in Cali triggered a landslide that claimed at least six lives. All the fatalities took place in the Siloe neighborhood where 14 homes were destroyed. During the overnight of March 31 – April 1, heavy rain affected parts of the Putumayo Department. A total of of rain fell within a few hours near the city of Mocoa. This caused the Mocoa, Sangoyaco, and Mulata rivers to overflow and send mudflows towards residences and infrastructure in the city of Mocoa by 3:00 a.m. Multiple neighborhoods were devastated in the disaster, with numerous residents caught off-guard. By the morning of6 April, at least 301 people were known dead, more than 400 were injured, and a further 314 were missing.
Ecuador
In Ecuador, at least 16 people were killed by floods or landslides. Coastal Manabí declared a state emergency and the country's largest city, Guayaquil in Guayas experienced abnormally high rain events. Higher elevation regions including Quito experienced severe rains, landslides, and sinkholes towards the tail end of the Coastal Niño event as the ITCZ began moving north towards its more usual latitude.
Peru
Much of the coastal desert region of Peru was particularly hard-hit with incessant, heavy rains starting in January 2017. Most impacted were the regions of Tumbes, Piura, and Lambayeque where a state of emergency was declared on February 3, 2017. These equatorial parts of Peru are typically dry throughout the summer but can be greatly impacted by climactic changes when adjacent ocean warms and the equatorial trough oscillates further south. During these occurrences, monsoon-like rains can fall in usually bone-dry ecosystems causing mudslides locally known as huaycos. The 2017 Coastal Niño was the worst to hit Peru since 1925. More than 115,000 homes were demolished, leaving approximately 178,000 people homeless. A total of 113 people were killed, 354 were injured, and a further 18 were missing. More than 2,500 kilometers of roads were destroyed and an estimated 1.1 million people have been directly affected by the floods. The United Nations Office for the Coordination of Humanitarian Affairs noted that 3 million people were at-risk for waterborne diseases. On March 16, a mudflow buried the village of Barbablanca; however, all 160 residents escaped. On March 27, 2017, the Piura River broke its banks and flooded the city of Piura and the towns of Catacaos and Pedregal Chico. In Piura, of rain fell in one day, three times the city's annual average and Catacaos had flood waters rise to high. Further south, La Libertad, Áncash, and Lima were also impacted. Trujillo experienced severe localized flooding in its ravines and Huarmey was badly flooded.
Elsewhere
In Brazil, Heavy rains on March 11–13, 2017, including in 24 hours, caused flooding across Rio Grande do Sul, killing 2 people, injuring 70, and leaving 10 others missing. Further south, in Chile, unusually heavy rains affected areas around Santiago starting in February 2017. Flooding and landslides killed at least eighteen people and left few others missing.
