Early in the morning on August 14, 2017, after three days of torrential rainfall, devastating floods and mudslides occurred in and around Sierra Leone's capital city, Freetown. Heavy rainfall extended throughout the country during the rainy season, causing one of the most deadly and destructive disasters in decades.

Because of a moratorium on housing construction that was not enforced, unorganized settlements and municipal works encroached on flood plains, resulting in narrower water passageways. During floods, Freetown's drainage systems are often blocked by discarded waste, especially in the city's poorer communities, contributing to higher levels of surface runoff.

The construction of large homes in hillside areas and unrestricted deforestation for residential purposes weakened the stability of nearby slopes and caused soil erosion which caused the mudslide at Mortomeh in Regent killed dozens and left thousand perished under the rubbles.

Sugar Loaf Mountain partially collapsed, triggering mudslides which damaged or completely submerged several houses and structures, killing residents – many still asleep – who were trapped inside.

The disaster affected another 12 settlements in the urban and rural districts of Freetown, and damaged 900 properties, covering 116,766 square meters from Sugar Loaf Mountain to Lumley Creek.
More than 3,000 people were left homeless by the disaster. By August 27, local government and ministry officials reported 1,000 fatalities during religious services honoring the victims. The final official death toll declared 1,141 dead or missing.

Several European countries responded with donations: the United Kingdom provided £5 million for clean drinking water and medicine, Ireland donated €400,000, Spain donated €50,000 and assembled a technical forensic team, and Switzerland spent CHF400,000 to provide sanitation and first-aid kits .

West African country donations included $500,000 from Togo, medical supplies distributed by Liberia, and pledges for support by Guinea and Nigeria.
Other governments such as China donated $1 million through their embassy in Freetown, and Israel sent an envoy supplying food and medical supplies. In response to the disaster, the UN arranged contingency plans to mitigate potential outbreaks of waterborne diseases.

The UN's migration agency allocated $150,000 in initial-response aid and mobilized personnel in Sierra Leone to assist in rescue operations and distribute supplies to survivors. WFP provided rations for 7,500 people.

EU authorized €300,000 for humanitarian aid on August on August 17, the International Federation of Red Cross and Red Crescent Societies (IFRC) approved CHF4.6 million worth of aid to be distributed through the Sierra Leone Red Cross agency for use over a 10-month period.