Preliminary Investigation of Critical Separation Distance Between Shacks in Informal Settlements Fire

Abstract

Approximately, one billion people across the globe are currently living in informal shack settlements with a large potential fire risk. Due to the small distance between shacks, a single shack fire may spread and could cause a large area of informal settlement to be burnt in a short period of time. In this work, the critical fire separation distance between shacks is first discussed and determined using a simple physics-based theoretical model. Aerial photography within geographic information systems (GIS) is then employed to verify the calculated results based on a real informal settlement burn scar in Masiphumelele, Cape Town, South Africa. The radiative heat fluxes along the centerline of the shack window, at different distances, are calculated to estimate the ignition potential of combustible materials in adjacent shacks. Meanwhile, the potential fire risks, assuming separation distance as a proxy for risk, pre- and post- a known fire in Masiphumelele are obtained and compared. It was established that the heat flux would decay from around 100 kW/m2 within 0.5 m to the value smaller than 0.1 kW/m2 at the distance of 3.5 m away from the shack, which can be considered as a relatively safe distance. The theoretical result agrees well with the minimum effective distance of 3.3 m in real fires occurred in Masiphumelele. However, a GIS analysis of the informal settlement layout in 2015 and 2017 demonstrates that, if the critical fire separation distance is more than 3.0 m, 97% of the settlement could be at risk in a single fire incident. Therefore, more research is required to improve the understanding of fire spread mechanisms in informal settlements.