Flood risk mapping and factors that motivate the affected community to continue living in the flood risk zones in Budalangi sub-county, Busia County, Kenya

Abstract

Floods are the most common and widely distributed natural hazards to life and property worldwide. In Kenya, floods are often declared national hazards. Nzoia River flowing through Budalangi Sub-County in Western Kenya, causes floods to this region annually threatening economic, physical, social and psychological survival to the inhabitants in the Basin. The study set up to undertake a flood risk mapping and assessment within Budalangi region and identify those factors that motivate the affected community to continue living in the flood risk zones. The specific objectives of the study were to map flood risk and safe zones within Budalangi, map land use land cover from Landsat satellite image of Budalangi sub-county, determine the land use elements at risk due to flooding, and to analyze the socio-economic factors that retain residence at flood risk areas. A sample of 162 households were systematically interviewed out of 15,245 households. The information obtained complimented secondary data obtained from shuttle radar topography mission (SRTM). The study applied GIS and remote sensing (RS) in the assessment of flood risks in the area. Mapping of land use land cover of the sub-county was done through the use of 2016 Landsat 8 image. Elevation analysis was done using void filled 2013 SRTM image. This analysis aided in delineating all features at risk. There were 61.1% female respondents, while 38.9% were male. Geographic positioning system (GPS) coordinates were pegged on sample locations as well as other elements that required elevation verification. Flood stage scenarios were hypothesized below and above the actual flood stage to determine locations for evacuation in case of various magnitudes of flooding. The features at risk were also evaluated by using existing land use land cover and an overlay analysis taken to determine the areas and land use at risk. The study found that 3.5km 2 of settlement was at a greater risk while 12.5km 2 of farmland were in danger of flooding. Further, the study found that 36% of the entire land cover was under farmland and 9% of total land cover was under aquatic-riverine vegetation, majorly in the shores of Lake Victoria and along River Nzoia. The study categorized the flood zones as high flood risk areas, moderate flood risk areas and low flood risk areas. The study further identified various regions within the sub-county which the affected people can be relocated to, and it was established that Budalangi High School, Bukangasi, Musokoto village, West Bunyala Location to East of Mundere has 90% safe zones. The study concluded that farmland was at a greater risk affecting 19% or 12.5km 2 of farmland and 3.5km 2 of buildup areas. Societal factors such as land acquisition, fertility and food security were found to be the main reasons why the community still strives to occupy this territory. The study recommends that settlements below 1143m ASL should be relocated to high ground areas such as Bukangasi, Musokoto and Budalangi High school, which are safe from floods.