Geo-Hydrological Hazard Impacts, Vulnerability and Perception in Bujumbura (Burundi): A High-Resolution Field-Based Assessment in a Sprawling City

Abstract

Rapid urbanization, demographic pressure, and sprawl of cities are key factors in the vulnerability and damage related to geo-hydrological hazards. Dysfunctional urban services that favor informal settlements are at the forefront of elements that increase vulnerability. Cases of cities that suffer from geo-hydrological hazards are increasingly reported in many regions, especially in tropical countries in the Global South. Yet, studies on such examples are rare and commonly overlook the human and societal components of hazard risks. Here, we focus on Bujumbura, a city in Africa that has experienced rapid unplanned growth and sprawl into unserviced areas because of the non-application or a lack of a valid urban planning law. After filling in the gap in data collected using high-resolution field surveys and focus group discussions, this study highlights various factors of vulnerability to geo-hydrological hazards in the urban area. Indeed, 108 events of flood and flash floods and 81 gullies were inventoried in Bujumbura between 1997 and 2021. These geo-hydrological hazards have had a significant impact, particularly on housing, and have caused increasing displacement of the population. This vulnerability is exacerbated by the inefficiency of the rainwater drainage system in the urban space. Our result demonstrates how the failure of the institutions responsible for urban management is at the top of all the causes of the vulnerability of the sprawling city. We anticipate that our empirical approach is an effective way to obtain concrete information to develop practical strategies to prevent and mitigate vulnerability to geo-hydrological hazards in urban sprawling contexts.

Keywords

• vulnerability
• flood
• flash flood
• gully erosion
• urbanization
• risk perception