Assessment of land use / land cover change, rainfall variability and their impact on flood risk vulnerability in osogbo, southwestern, nigeria.
| dc.contributor.author | GLADYS, ODUMERUTITILAYO | |
| dc.date.accessioned | 2023-05-13T18:00:39Z | |
| dc.date.available | 2023-05-13T18:00:39Z | |
| dc.date.issued | 2015 | |
| dc.description | 115p | en_US |
| dc.description.abstract | This study identified the potential causes of flooding in Osogbo and its adjoining towns; produced a land cover map of the study area; and modeled the watershed area of the Osun River for flood assessment and mapping using geo-spatial techniques. These were with the view to determining the vulnerability of the study area to flood hazard. The study used both primary and secondary sources of data collection. Multi temporal Landsat TM, ETM+ images of the study area for 1986, 1991 and 2014 were acquired, processed and classified. Rainfall data spanning a period of 28 years was collected and used. Post-classification comparison was done to determine the historical land use/land cover change in the study area. A digital elevation model was derived to understand the topology of drainage patterns and flow process in the study area. Field survey was carried out to determine historical flood extent using a Geographic positioning system (GPS) and questionnaire survey instrument. The weighted layers (ranking) derived from the defined datasets was combined using overlay operation from spatial analyst tool in ARCGIS software to determine flood hazard zone. The study area was classified into five flood prone zones based on land use distance and elevation data (Old-garage, Oke-fia, Gbodofon, Gbomi, and Kola-balogun) with the total population of 34,620). A total of 346 respondents (One percent of the population) were interviewed using purposive sampling method. The results showed that the Osun river watershed clearly demonstrated that urban area has increased to 30.21% in the year 2014 compared to only 4.42% in 1986 from the land use/land cover classification map. Continuous deforestation at an alarming rate had reduced the secondary forest from 50.12% in 1986 to 40.12% in 2014. About 19.4% of respondents attributed the cause of flooding to the Osun River overflowing its bank, 27.2% mentioned heavy rainfall, 14.5% agreed that it was as a result of the built-ups around the flood plains, 27.2% strongly agreed that it was caused by the blocked drainage while just 11.5% agreed that the topography of the land could be a causative factor for flooding. The Annual mean rainfall data for the year 2010 was the highest with 140.98 mm, when compared with the years within the period of study. In the hazard zoning and vulnerability assessment, areas close to the OsunRiverwas categorized into high vulnerability (930-1033 m), moderate vulnerability (1067-1102 m) and low vulnerability (1136-1240 m) according to the elevations of the study area. The terrain of the study area was generally undulating and descended from an altitude of over 1244.14 to 923.736 m. Most areas in the study area were situated in the very high and moderate flood risk zones which were found to have elevations of below 950 -1300 m and 1067-1102 m above sea level. The study concluded that Land Use/Land Cover dynamics, continuous deforestation, increase in the impervious surface, floodplain encroachment, heavy rainfalland the topography of the land surface have an impact on the flood risk vulnerability of the study area. | en_US |
| dc.identifier.uri | https://ir.oauife.edu.ng/123456789/5596 | |
| dc.language.iso | en | en_US |
| dc.subject | Assessment | en_US |
| dc.subject | flooding | en_US |
| dc.subject | Osogbo | en_US |
| dc.subject | assessment | en_US |
| dc.subject | hazard | en_US |
| dc.title | Assessment of land use / land cover change, rainfall variability and their impact on flood risk vulnerability in osogbo, southwestern, nigeria. | en_US |
| dc.type | Thesis | en_US |