RESIDENTIAL BUILDING VULNERABILITY TO WINDSTORM DISASTERS IN IBADAN, NIGERIA, 2005 to 2015

Abstract

Climate-induced disasters which negatively affect lives and properties are on the increase in the cities. Ibadan metropolis has experienced several devastating windstorms between 2005 and 2015. During windstorms, residential properties are the most often affected, resulting in injuries and fatalities. Studies on climate related disasters had focused largely on flooding and drought with little attention paid to windstorm. This study, therefore, was designed to analyse the vulnerability of residential buildings to windstorm disaster in Ibadan, Nigeria.

Concept of Vulnerability guided the study while the survey research design was adopted. Using a purposive sampling technique, five most severe windstorm disasters out of 21 that occurred between 2005 and 2015 were selected from the list provided by the Oyo State Emergency Management Agency. The disaster status of the selected windstorm were determined using United Nations Development Programme Framework. Out of 1,853 residential buildings damaged by windstorms 1,115 (60%) that had been repaired and re-inhabited were geo-referenced for subsequent analysis. A questionnaire containing socio-economic characteristics (age, sex and income); housing and neighbourhood characteristics (age, height, wall material, roof types, topographical elements and wind direction) was administered on the household heads in the geo-referenced buildings. The geo-referenced building locations were overlaid on the administrative map of Ibadan to determine windstorm track. Ten In-depth Interviews (IDI`s) were conducted on victims of the windstorm disasters. Quantitative data were analysed using descriptive and inferential statistics (logistic regression, analysis of variance and nearest neighbour analysis) at p≤0.05. Qualitative data were content analysed.

Respondents’ age was 55.7±13.8 years, 46.3% were males and 24% earned less than N10, 000.00 monthly. About 46% of the buildings affected were more than 80 years old. Buildings generally devastated were one floor (44.9%). Mud buildings (54.9%) were mostly vulnerable and hip-roof building devastation (84.3%) was considerably high. Most residential buildings (65.8%) in neighbourhoods with relatively low elevation (171 to 190 meters) were considerably devastated by windstorm disasters between 2005 and 2015. However, 12.5% of buildings devastated were on hill crests (211 to 230 meters), 11.4% on the troughs (151 to 170 meters) and 10.2% up-hill (191 to 210 meters). Up-hill buildings were mildly devastated. Neighbourhoods located relatively on low lands were more vulnerable to windstorm disasters. Windstorm track (South West Trade Wind (78%) and North East Trade Wind (22%)) traversed the old quarters (traditional neighbourhood). Factors such as roofing style, (ß=-.2.74), materials used for construction (mud buildings) (ß=-1.19), vegetal cover (ß=17.16) and elevation, (ß=-.66) significantly influenced residential buildings vulnerability to windstorm disaster in Ibadan. Numbers of residential buildings devastated by windstorms varied significantly across residential neighbourhoods F(2,1004)=3.275. Devastated residential buildings were clustered (I: 0.482538), indicating hotspots of windstorms vulnerability in Ibadan. Age of buildings and materials used for construction were the perceived causes of windstorms disasters.

The vulnerability of residential buildings to windstorm disaster in Ibadan Nigeria was influenced by wind direction, vegetal cover and elevation. Therefore, the adoption of tree planting should be of priority to residents and policy makers.