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AUTHOR(S): Blanche Nabila Dohnji, Mabel Nechia Wantim, Kulu Eric Ndive, Asong Fred Zisuh
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ABSTRACT Flash floods are usually associated with short, high intensity rainfall and they are characterized by short response time between 4-6 hours. This study sought to assess the following: i) the causes of flash floods in Buea Municipality; ii) the effects of the 2020 flash floods and damage assessment in two of the most affected localities (Bonduma and Sandpit); and iii) the social and physical parameters that increase vulnerability to flash floods in Bonduma and Sandpit. A descriptive research design was used to identify the causes and effects of flash floods in Buea. The 2020 affected areas: Bokwai, Bonduma, Bokoko, Great Soppo, Buea Town and Bokwaongo, were selected using purposive and stratified sampling method. Questionnaires, key informant interviews, focus group discussions and observations were used to collect field data. SPSS version 23 was used to analyze the data. The ENSURE and Flood Vulnerability Index methodology were used to carryout physical and social vulnerability assessment respectively in the two most affected localities. Parameters were chosen for the physical (building type, and construction properties) and social (age, employment status, education) vulnerabilities. Field ground truthing was used to collect field data, while satellite imagery from the Landsat sensor (Landsat TM and Landsat 8) was used to get land use/land cover changes for the sampled communities for the past 32 years (1986 to 2018) analysed using ENVI 5.1. GPS coordinates were collected from field mapping, and supplemented with shape files of buildings extracted from the OpenStreet Map software to assess damage and delineate the flash flood 2020 affected areas processed using ArcGIS 10.7. Findings from this study revealed that the main causes of flash flood as per the respondents’ perspective were: heavy rainfall (41.5 %), wanton clearing of vegetation (17 %), climate change (15.6 %), topography (25.9 %), unsustainable building practices (43 %) and poor waste disposal practices (57 %). While the main effects as observed during the 2020 flash floods were: damage to infrastructure (37.6 %), agricultural losses and loss of life. A significant decrease (-46.95 km2) was observed in the area covered by plantation/farmland; while settlement significantly increased (29.93 km2). These two land cover classes were the major contributing factors to flash floods in the affected localities. Vulnerability analyses showed that Bonduma had a moderate vulnerability index of 3 compared to Sandpit with a low to moderate vulnerability index of 2.5 for the physical and social vulnerability classification on a scale of 5. The flash flood map generated showed that, 146 houses were affected within a surface area of 103,873 m2 in Sandpit locality while in Bonduma just 94 houses were affected by the 2020 flash flood within a surface area of 134,429 m2. Vulnerability assessment of flash floods within the two selected localities in Buea Municipality showed Bonduma to be more vulnerable. |
KEYWORDS Flash floods, physical vulnerability, social vulnerability, ENSURE methodology, land cover, Buea |
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Cite this paper Blanche Nabila Dohnji, Mabel Nechia Wantim, Kulu Eric Ndive, Asong Fred Zisuh. (2024) Vulnerability Assessment of Flash Floods within Buea Municipality Using Field and Remote Sensing Techniques: Case of the 2020 flash flood. International Journal of Environmental Science, 9, 11-26 |
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