Exposure and physical vulnerability to geo-hydrological hazards in rural environments: A field-based assessment in East Africa

Abstract

Geo-hydrological hazards (landslides and floods) are often associated with large impact on physical infrastructures, affecting strongly the exposed population. Understanding in detail the nature of exposure and what determines the extent of impact is a prerequisite for building resilient structures and reducing vulnerability. However, such information is rarely available, especially in rural communities where people are often the most vulnerable. In this study we document the impact of landslide and flood hazards in 17 sub-counties in the mid- and south-western parts of Uganda between May 2019 and March 2021 through extensive fieldwork involving local stakeholders. We quantify the economic value of the physical damage of landslide and flood hazards on exposed buildings, roads and bridges. We then determine statistically the factors that influence the physical vulnerability of the elements at risk based on damage ratios, i.e. monetary value of each individual building damage divided by its initial construction value. A total of 91 and 212 buildings were documented from the landslide and flood hazard affected zones, respectively. Out of the 91 landslide affected buildings, 71 % were completely destroyed and 4 % severely damaged, while 19 % had minor-to-no damage at all. For floods, 37 % of the buildings were completely destroyed and 6 % were severely damaged, while 53 % had minor-to-no damage. The impact of landslides and floods is unevenly distributed across the study sub-counties and the extent of loss they cause also vary with exposed elements. Based on parameters that could be documented through our field-based approach, we conclude that while the physical vulnerability of buildings to landslides is equally associated with both landslide size and building structural characteristics, the physical vulnerability due to floods is largely linked to the flood depth. This quantitative study therefore shows the need for plans, policies and strategies geared towards improving the building resistance to landslides and controlling settlements in flood prone places.