Conceptualising a GIS-based risk quantification framework for fire spread in informal settlements: A Cape Town case study

Informal settlements are home to approximately one billion people globally and are growing due to rapid urbanisation in less economically developed countries. Their dense layouts, often combined with light, combustible building materials make them highly vulnerable to fires. In some cases fires have spread through hundreds or thousands of homes in a single fire, rendering the inhabitants homeless. Tackling this issue requires a sound understanding of the many spatial factors which can contribute to fire spread between individual dwellings and into the wider settlement. This paper presents initial methods for assessing and quantifying fire risk in informal settlements due to a variety of spatial factors in the case of Cape Town, South Africa – a city which has a notable history of devastating informal settlement fires. GIS techniques were used to obtain data to build a model for the quantification of risk imposed by the settlement layout with respect to three key metrics; dwelling spacing, edge density and critical patch size. The results of the risk model and data of past fires suggest that the settlement layout is a critical factor in determining the ability of large fires to establish within a settlement. A framework for additional infrastructural and environmental risk is also presented, identifying the need for a wide-ranging interdisciplinary approach to the problem of urban fires.