The cost of rapid and haphazard urbanization: lessons learned from the Freetown landslide disaster

Abstract

Urbanization has been linked to destructive geo-hazards that can cause loss of life, destruction of property, and environmental damage. On August 14, 2017, a devastating geo-hazard chain-a debris slide, debris flow, and sediment-laden flood-in Freetown, Sierra Leone resulted in at least 500 deaths and over 600 missing persons and the destruction of hundreds of houses. This study uses 10 years of high-resolution satellite images to conduct a remote sensing analysis of the disaster. Although rainfall was the trigger, rapid and haphazard urbanization acted to increase both hazard and vulnerability. Specifically, poor urban planning with inadequate consideration of risk led to housing construction in dangerous areas; clearance of hillside vegetation increased erosion potential; very low cost buildings using frail construction material and methods lacked resilience; and insufficient risk management led to weak emergency response.

Implementing the Sendai Framework in Africa: Progress Against the Targets (2015–2018)

“…Over 2.2 million people were affected and approximately 1300 fatalities were recorded due to impacts of the two cyclones (Pelling and Garschagen 2019;Weems 2019). In 2017, a mudslide in the outskirts of Freetown, Sierra Leone killed over 1100 people with 6000 people affected (Cui et al 2019). Droughts continue to persist in the Southern African region, resulting in food shortages in some countries.…”

The State of Remote Sensing Capabilities of Cascading Hazards Over High Mountain Asia

“…(1) freeze-thaw, which can cause frost shattering of bedrock (Dredge, 1992) and generation of talus, or weakening or creep of unconsolidated sediment (Daanen et al, 2012;Zhou et al, 2018); (2) sustained rainfall or snowmelt, which can destabilize soils (Cui et al, 2019); (3) chemical weathering, which can weaken bedrock and generate talus (Avtar et al, 2011); (4) thinning of glaciers and debuttressing (removal of the physical support) of moraines or weakened bedrock or tributary glaciers (Kääb et al, 2006); (5) thawing of permafrost or ice-cored moraines; (6) gully erosion by surface streams or subsurface piping, which can undermine glaciers, debris, or bedrock; (7) prior earthquakes or joint fracturing of bedrock ; (8) deforestation and other vegetation changes (Pathak, 2016;Hashim et al, 2017); (9) construction (Pathak, 2016); and commonly a combination, e.g., bedrock weathering, deforestation, land use conversion and construction, and sustained precipitation (Cui et al, 2019), or bedrock fracturing, vegetation change, and sustained precipitation . Commonly, minor landsliding itself can destabilize slopes and condition them for larger subsequent failures triggered by earthquakes or rainfall (Pathak, 2016).…”

“…Penetration of rainwater beneath hanging glaciers may decrease basal shear stress on steeply sloping beds, leading to serac falls (toppling blocks of ice). Road building and deforestation for agriculture or urban expansion commonly contribute to hillslope destabilization (Petley et al, 2007;Cui et al, 2019). Preconditioning may happen hours to decades before a trigger initiates a landslide or flood.…”

A comparative Geological, Tectonic and Geomorphological assessment of the Charlotte, Regent and Madina Landslides, Western Areas, Sierra Leone

“…Despite the socio-economic and geomorphologic impacts associated with landslides (Ngeku and Mathu, 1999;Ngeku et al, 2004 andJacobs et al, 2016), which are expected to increase with global climate change (Nugraha et al, 2015), studies are still rare in the Africa continent ( The situation is even worst in Sierra Leone, which has very limited and restricted scientific landslide studies (e.g. Thomas, 1983Thomas, , 1994Thomas, & 1998Cui et al, 2019, Redshaw et al, 2019; and Lahai and Lahai 2019), amidst a surge of landslides in its capital city. This is also supported by the exclusion of localized landslide crises in the International Emergency Database (EM-DAT) and the Global Disaster Identifier (GLIDE), despite its serious impacts; indicating a dearth in landslide knowledge in this part of the world.…”