The 2017 Regent Landslide, Freetown Peninsula, Sierra Leone

Abstract

At 06:50 on Monday 14 August 2017, a hillslope on the Freetown Peninsula, Sierra Leone, collapsed, sending 300 000 m 3 of debris into the flooded valley below. As this debris mixed with floodwater it became a sediment-laden flood which entered a drainage channel and travelled 6 km to the coastline. The event destroyed nearly 400 buildings, claimed the lives of an estimated 1100 people and affected c. 5000 people. The mechanism was a two-stage rainfall-triggered landslide followed by a channelized debris-laden flood. The processes were similar to the nearby 1945 event in Charlotte, which killed at least 13 people. Geomorphological mapping has identified evidence of hundreds of other large landslides that occurred before modern records, providing an appreciation of the slope processes affecting the Freetown Peninsula. Following the 2017 Regent Landslide, rehabilitation of the affected area involved a risk-reduction strategy that centred on reducing population exposure. These events are a reminder that the steep slopes and valleys across the Freetown Peninsula are highly susceptible to rainfall-triggered landslides which, given the topography, have a high propensity to generate high intensity landslides and debris-laden floods. Future urbanization must consider whole-catchment management, flooding and slope engineering issues to provide lasting landslide risk reduction.