From May 14, 2016 onwards a low-pressure zone above Sri Lanka caused torrential rainfall all over the country, and in some places it was the heaviest recorded rainfall in more than 18 years. Several rivers, including Kelani River, Kaluganga, Mahaweli River, Deduru Oya, Yan Oya, Maha Oya and Attanagalu Oya, observed rising water levels, which caused widespread flooding. Heavy rainfall was recorded in Deraniyagala (355.5 mm), Colombo (256 mm), Katunayake (262 mm), Ratmalana (190 mm), Mannar (185.5 mm) and Trincomalee (182.4 mm). Further, districts such as Kurunegala, Kegalle, Nuwara Eliya, Ratnapura, Kalutara, Kandy, Puttalam, Batticaloa and Anuradhapura also received more than 100 mm of rainfall. The resulting floods were the worst in 25 years. As another result of the rainfall, severe landslides occurred in several divisions in the Kegalle district. The worst landslide occured in the Aranayake division in the Kegalle district where three villages were completely swept away and buried under mud and debris.
The large extent of the flooding is partially linked to the El Niño phenomenon, which has affected the Asia and the Pacific region. Initially, Sri Lanka experienced lower than average rainfall (with prolonged water shortages and drought), which was then followed by sudden heavy rains and storms causing floods and landslides.
According to the National Disaster Relief Services Centre (NDRSC), which is part of the Sri Lankan Ministry of Disaster Management (MDM), 24 districts out of a total of 25 districts countrywide were affected by the flooding and landslides. The floods and landslides affected approximately 493,319 people (124,398 families). 93 people died (36 women, 43 men, 10 children, 4 bodies could not be identified), 33 were injured and 117 are missing. The majority of the deaths (50, i.e. 54%) occurred due to the landslides in the Kegalle district. Additionally, the number of missing people (99, i.e. 85%) is highest in Kegalle.
Overall, 58,925 houses were affected, of which 6,382 were destroyed and 52,543 were damaged. Over 85 percent of the affected houses are in Colombo and Gampaha districts. District Secretaries had established 350 Safety Centres to house people evacuated from inundated areas and unsafe locations in landslide prone districts. At its peak, 114,035 people (29,474 families) stayed in these centres. Other affected people either stayed with friends or family or in makeshift locations, rooftops or above the ground floor of inundated houses.