Severe flooding in South America

  • NASA MODIS satellite images from Worldview. February 2017.

    Sea surface temperature anomalies for February 2017 from NOAA's OISST dataset. Image from NOAA

  • Severe flooding in South America
    08.04.2017 17:42

    Heavy rains this year have caused repeated severe flooding across western parts of South America, including Peru, Columbia, Ecuador and Chile. Rainfall totals have been anomalously high with some areas receiving 4 times the average rainfall for the last week of March.

    One of the worst affected regions has been western Peru where prolonged and excessive rainfall has brought devastating landslides to mountain villages. So far, in Peru, the floods have been reported to have killed more than 100 people, with more than 100000 left homeless. Thousands of homes have been destroyed with damage to public buildings and infrastructure.

    Columbia has also been particularly badly affected in recent weeks. On the night of Friday 31st April, heavy rain in the mountains near the city of Mocoa, in Putumayo, south-west Columbia, was reported to give 130 mm (5 inches) of rain within a few hours. This caused rivers to burst their banks and brought a devastating mudslide to Mocoa. The floods killed at least 314 people, many of whom were children, with more than 100 still missing.

    Cause of the excessive rainfall and El Niño
    The high rainfall has corresponded to anomalously high sea surface temperatures of more than 2.5C above average in the eastern Pacific, just off the coast of Peru. This can often precede the development of an El Niño, whereby sea surface temperatures in the central Pacific Ocean are high. Under these conditions western parts of South America typically see higher than average rainfall as has been seen this year. However, El Niño is currently in a neutral phase, with slight cool anomalies seen in the central Pacific, despite the warmth over the eastern tropical Pacific. There is therefore uncertainty as to the development of an El Niño this year but with an increasing chance into the Autumn.

    The outlook for South America
    Over the next few weeks, it looks like wet conditions will continue to affect Ecuador as well as northern parts of Peru. However, rainfall over Columbia looks to temporarily ease.

    By: Callum Stewart