Vulnerability of key urban infrastructures to geo-hydrological hazards: how endangered is the city of Bujumbura?

In urban areas, networks and life-support systems, such as roads, power lines and drinking water pipes, are key infrastructures which contribute to the functioning of the city. Their damaging or destruction can lead to harmful consequences for the population. Such situation has already occurred in several African cities following the impact of a hazard of natural or human-induced origin. Bujumbura, the economic capital of Burundi, is no exception to such scenario, particularly as a result of geo-hydrological hazards which regularly affect various neighborhoods of the city: floods, flash-floods, river bank collapse, large urban gullies. For instance, the February 2014 flash flood damaged several key infrastructures in the north of Bujumbura, including the National Road number 1, a medium-voltage line and drinking water pipes.

The goal of this study is to show how, in an urban system like the city of Bujumbura, the vulnerability of these key infrastructures to geo-hydrological hazards can lead to the fragility of a large territory. This vulnerability is influenced by weaknesses related to their wear or age, their construction technique, and their dependence on external systems for their effective functioning. In addition to their own weaknesses, these key infrastructures are exposed to several natural hazards that can lead to their damage or destruction. In Bujumbura, the geo-hydrological hazards that regularly impact the city are accentuated by the lack or outdated rainwater drainage facilities and the inadequacy of the urban development plan.

After listing, locating and characterizing all the infrastructures that play a role in the life of the population in the urban environment, a classification, based on a participatory approach, was developed to select those on which the vulnerability assessment focused. Six forms of vulnerability (intrinsic, dependency, hazard exposure, control capacity, alternative operation, and crisis management) were assessed for each key infrastructure. To assess each form of vulnerability, interviews were conducted with facility managers (28) to supplement the data from the literature and field collection. Geometric weighting was performed to highlight the most vulnerable infrastructure that could disrupt the functioning of others and, by extension, that of the city.

The results of this study show that several road sections in the center and at the exit points of Bujumbura, as well as the drinking water treatment plant and the pumping stations, stand out among the most vulnerable infrastructures. Continued efforts are required to maintain, protect, and strengthen these networks and life-support systems in the face of geo-hydrological hazards, as their damage or destruction due to cascading effects caused by dependence on, or wear and tear of, infrastructure can affect a much wider area than just the hazard impact zone.