Vulnerability of Built Environment to Flooding in African Cities

Abstract

Urban built structures and lifelines in African cities are particularly vulnerable to extreme weather-related events such as flooding. This chapter provides an overview of the activities and the findings related to the vulnerability to flooding of the urban built environment in the context of the CLUVA project. First, the urban hotspots to flooding for the built structures and the lifelines are identified for three African case study cities. In the next step, a probabilistic methodology is employed in order to perform micro-scale evaluation of building vulnerability and risk to flooding for the case study city of Dar es Salaam based on historical rainfall data. This methodology is developed specifically for vulnerability assessments based on incomplete knowledge and relies on various data-gathering techniques such as orthophoto boundary recognition, field surveys and laboratory tests. The micro-scale evaluation of the building vulnerability is also performed using rainfall data for a projected 1-year interval in 2050. The results in terms of economic loss and number of people affected are discussed and compared to the evaluation performed based on historical rainfall data. In this comparison, the negative effect of urbanisation on flooding risk is emphasised. The findings presented in this chapter can be translated into strategic adaptive measures for urban structures and lifelines to flooding.