Flood Vulnerability Assessment of Ibadan City, Oyo State, Nigeria (original) (raw)
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An Assessment of Flood Vulnerability Areas in ETI-OSA Local Government Area, Lagos State, Nigeria
There has been a significant increase in flood occurrence with their devastating impacts leaving lasting imprints in the coastal areas especially. To this end, the study assessed flood vulnerability areas in the Eti-Osa area of Lagos. The application of Geographical Information System (GIS) and remote sensing are used in preprocessing and processing acquired spatial information. Five flood vulnerable zones are identified from the analysis. They are very highly vulnerable zone (23.59%), highly vulnerable zone (12.23%), moderately vulnerable zone (10.04%), less vulnerable zone (9.52%), and none-vulnerable zone (44.62). The residential area is vulnerable to socioeconomic development because of loss and damages to the properties of residents. The study concludes with the recommended management strategies to mitigate the adverse effects in the study area
This study makes use of the integrated approach of Remote Sensing and GIS techniques in flood management with the goal of identifying areas vulnerable to flood hazard in Ibadan Metropolis. Ibadan is the largest indigenous city in the continent of Africa and had experienced a lot of various severities of flood occurrences in the last fifty years. Topographic Map and Landsat TM image of 1993 and 2000 respectively were processed, scanned, digitized, interpolated, classified and overlaid using ILWIS 3.3 academic and ARC GIS 9.2 software modules to generate classified land cover map, Digital Terrain Map (DTM), Triangulated Irregular Network (TIN) and flood vulnerability map of the study area respectively. The results obtained shows that, areas lying along the banks of River Ona and River Ogunpa are most vulnerable to flood hazards with the vulnerability decreasing towards the northern part of the city, much of the area is built up with improper planning and this gives rise to high vulnerability to flash flood hazards. The Odo Ona, Idi Isin, Eleyele, Olopometa and Molete areas are the most vulnerable to flood threat. The incessant violation of land use plan, unchecked population growth, old nature of the structures and poor materials used in the construction of the houses make the areas vulnerable to flood hazard. In reducing the vulnerability of these areas from flood there is need for improved land use planning, removal of structures from River Ona and Ogunpa flood plains around the city, intensify environmental education to the residents and enhance the active participation of government agencies in the continual generation of flood vulnerability maps of urban centres. 1. Introduction Flooding is the commonest natural hazard that can happen any time in wide variety of locations within rainy season due to high intensity of rainfall events. The projections of climate change trends indicate increase of the occurrence of the intense rainfall events both in terms of the intensity as well as their frequency (IPCC, 2007). The projected high intensity rainfall events coupled with the changes in the land use patterns are expected to have implications on the intensity of river flooding and local flash flooding in a flood plain region and can significantly alter the spatial extent of future flood risk. A flood is an overflow of expanse of water that submerges the land. Floods are among the most destructive acts of nature. Over the past thirty years, floods have been the most catastrophic natural disaster affecting, on average, about 80 million people per year or half of the total population affected by any natural disaster, causing economic damage worth over US$11 million annually around the world (IFRCRCS,1998). As human activities downstream of rivers increases, it results to increase in greater flood damage, floods are also increasing in size and frequency due to human activities in the upstream section of the river system (Dutta et al., 2006). Worldwide , flood damages to agriculture, properties and public utilities amount to billions of dollars each year in addition to the loss of precious human and animal lives. In most cases, flooding is caused by a river over-spilling its banks. This can be due to excessive precipitation, combined with inadequate channel capacity. Over-spilling can also occur due to obstruction in the river bed. Flooding can also occur at confluences of streams when the main river is in high stage and backs up into the tributaries and areas there about. The role of Geographic Information Systems (GIS) in disasters analysis and management is typically important in critical life saving measures and has been using in developed countries in the last two decades. Advancements in remote sensing (RS) technology and GIS the help in real time monitoring, early warning system and quick damage assessment of flood and drought disasters (Ishaya et al., 2008a. A Geographic Information System is a tool that can assist floodplain managers in identifying flood prone areas in their community. With a GIS, geographical information is stored in a database that can be queried and graphically displayed for analysis. By overlaying or intersecting different geographical layers, flood prone areas can be identified and targeted for mitigation or stricter floodplain management practices. Remote Sensing can be very effective for flood management in two ways; firstly by detailed mapping that is required for the production of hazard assessment maps, hence for input to various types of hydrological models, and secondly by developing a larger scale view of the general flood situation within a river basin with the aim of identifying areas at greatest risk and in the need of
Geospatial Assessment of Flood Vulnerability Areas in Lagos Metropolis, Nigeria
Asian Journal of Basic Science & Research , 2024
Flooding is now a common event in Nigeria, causing harm to both people and infrastructure progress. Areas with lower elevations are more significantly impacted by floods. Twenty (20) LGAs in Lagos are currently being evaluated to pinpoint areas at risk of flooding to better manage flood risks and reduce the impact of natural disasters. This research seeks to evaluate specific flood-prone locations on the map of Lagos using GIS technology and provides important recommendations to mitigate the effects of flooding in those regions. Research indicates that areas like Epe, Badagary, Eti-Osa, and Ibeju-Lekki are at a high risk of flooding, whereas Ifako-Ijaiye, Agege, Alimosho, Ikeja, Mushin, Shomolu, Lagos Mainland, and Ajeromi/Ifelodun have a lower vulnerability to floods. Hence, it is recommended that regions susceptible to flooding consistently check water levels in the rainy season and release water from reservoirs to avoid property damage and loss of life. Moreover, further measures include enhancing environmental knowledge for locals in flood-prone regions and engaging government agencies and the community in community-driven flood risk management. The findings and recommendations of this research are expected to be implemented to prevent potential disasters in the most flood-prone areas of Lagos.
Flood Vulnerability Mapping using Geospatial Techniques: Case Study of Lagos State, Nigeria
Asian Journal of Applied Science and Technology
Flood is one of the natural disaster known to be part of the earth biophysical processes, which its occurrence can be devastating; due to mostly anthropogenic activities and climatological factors. The aim of the research is to identify and map the extent at which the impact of flood due to intense rainfall and rise in water in the study area using geospatial techniques and the specific objectives are to carry out terrain analysis of the study area and to generate flood indicator maps of the study area. The study analyzed rain fall data;, the drainage system and Shuttle Radar Topographic Mission (SRTM 30m) of the area. ArcGIS 10.8 was to modelled and to generate the contributing factors map of the study area. The drainage system was generated through on-screen digitization of topographic map of scale 1:50,000 of Ondo South-West. The mean annual rainfall of Lagos State was generated in the ArcGIS environment from the rainfall data through spatial analysis tool. The SRTM was used in t...
Journal of Geography, Environment and Earth Science International
A flood is an overflow of water that submerges land that is usually dry. Flooding may occur as an overflow of water from water bodies, such as river, lake or ocean, in which the water overtops or breaks levees, resulting in some of that water escaping its usual boundaries, or it may occur due to an accumulation of rain water on saturated ground in an area. To find out the most vulnerable communities, the Digital Elevation Model (DEM) and location data of selected communities were used. The Image Re-class and Map Overlay were performed on QGIS software to identify communities that are most affected. The result shows that the region has no river channel that discharge excess water easily. It also shows that four, out of twelve settlements were located at the high risk zone. The settlements are Uniport, Omuoda, Omuahunwo and Okparagwa. It was recommended that the high risk zone in the area should be provided with artificial water channel that will contain and convey surface sun-off to ...
Urban Flood Vulnerability Mapping of Lagos, Nigeria
MATTER: International Journal of Science and Technology, 2017
The paper aimed to demonstrate how the application of HEC-RAS and GIS techniques can be utilized for better results when carrying out a flood vulnerability mapping and assessment. Digital interpretation that uses HEC-RAS and GIS to conduct hydraulic modelling, flood inundation mapping and visualization were adapted. Similarly, Digital Terrain Model (DTM) and aerial imagery of lansat8 OLI of the study area were used. The data were analysed with the aid of ArcGIS 10.1 application with HEC-GeoRAS tool extension and HEC-RAS 4.1 software application. The results showed: 1) the flood vulnerability map of Lagos (Figure 4) generated using the combination GIS techniques and RAS packages. The flood risk depicted shown areas that have 1 % probability of flood occurrence in 100 years; 2) The topography of Lagos (Figure 5) indicated the pattern of the city terrain to be relatively flat in the centre and it also has few meters high above sea level especially in the southeastern areas; 3) of the 20 local government areas Lagos state (Figure 6) only two (Agege and Ifako) were found not to be at risk of flooding. We concluded that flood vulnerability of this kind is important for Nigeria and other countries to aid decision on flood disaster planning.
The study aimed at assessing flood prone areas in Uyo Capital City with a view to suggesting control measures. It used 2008 NigerSat imagery, soil texture, rainfall, and road network data of Uyo. With Multi-criteria evaluation technique, the use of Geographic Information Systems (GIS), Global Positioning System (GPS), Digital Elevation Model (DEM) and single output map algebra were employed to generate flood hazard map of Uyo. The DEM was used to generate contours, terrain elevation, slope, and aspect surfaces, where aspect provided the direction of slope that contributed to flood inundation. Flood mapping was done to determine flood locations based on a 3D terrain assessment while flood hazard assessment formed the basis for flood control in the area. From the result of the study, flood hazard areas in Uyo Capital City were identified and classified into high, moderate, and low hazard zones. Based on this classification however, flood control measures have also been rated as critical, less critical, and non-critical respectively. Out of the 25 flood locations captured during the 2012 flash flood event, twelve locations were found on the critical control zones while thirteen were found on the less critical control zones. Based on the findings from this study, it was however suggested that town planners, construction companies and individuals should work in consultation with Geographers, Hydrologists and other stakeholders in the field who have adequate knowledge of the terrain and the technical ability in flood hazard modeling. Additionally, non-structural flood control measures have also been strongly advocated for implementation in the capital city of Uyo.
Disaster occurrences are on the increase all over the world and large numbers of people are constantly exposed to the risk associated with these disasters including flooding. Urban areas, especially in developing countries, are highly vulnerable with increasing threat of flood; there is therefore need for an assessment of flood vulnerability and capacity for implementing disaster risk reduction (DRR) programmes in communities. The study focuses on the use of Remote Sensing and Geographic Information System technology to propose an effective assessment of the vulnerability of Kubwa town to flooding and the capacity for implementing a DRR programme in the area. Satellite imageries for three periods: 1987, 2001 and 2006 were used for an overall assessment to produce a contemporary land use maps. Comparative analyses of the old land use map, the master plan and the derived land use map shows that there has been consistent changes in the original land use compared to the current, evidenced in the increase of areas allotted for residential purposes (20.54% to 75.6%). Buffering analysis was carried out to determine areas that fall within the floodplain. Digital Terrain Modelling (DTM) and slope analysis were used to re-classify the area into different levels of vulnerability. The analyses showed that the central part of Kubwa, which is the most populated area, is most affected by flood incidences due to soil sealing resulting to infiltration. Other features of this area are encroachment on the flood plains, clogging of the drains and lack of land use planning. The study therefore recommends the need for improved land use planning, enforcement of standards and codes, Community Education/ participation, among others.
International Journal of Society Systems Science, 2011
Spatial information technologies are changing the way in which decisions are taken in relation to the environment. Geographic information system (GIS) is one of such technologies that help to generate products useful in terrain analysis. In Nigeria, especially in the study area, floodplains and river corridors have been misused resulting in severe environmental hazards. Up-to-date information is required to assist decision makers in tackling the problems arising from the misuse of our floodplains. To this end, the capability of remote sensing (RS) and geographic information systems have been explored to generate products such as digital elevation models (DEM), slope maps and risk analysis maps which give useful information about the terrain. In our opinion, the information provided by these technologies can significantly improve strategic decision-making processes in floodplains and river corridors worldwide.
Geospatial Analysis of Flood Problems in Jimeta Riverine Community of Adamawa State, Nigeria
Floods are among the most devastating natural disasters in the world, claiming more lives and causing more property damages than any other natural phenomena. In recent times, the incidence of flooding across Nigeria has left both the government and the governed devastated. It is no longer news that flooding and its attendant consequences are injurious to man while the spatial dimensions are often not mapped. This study, therefore, examined the nature of water level/extent and vulnerability in the riverine community of Jimeta, Adamawa State. Using time series analysis, four epoch satellite images covering the study area was used to evaluate the geospatial coverage of water along the watercourse of Upper Benue bordering the study area. Using ILWIS 3.8, ArcGIS 10.1 and statistical analysis, the spatial extent and vulnerability of settlements was mapped. Highly vulnerable (50m buffer) were differentiated from low risk zones (100m buffers). Study revealed that besides rainfall, excess water from Cameroun dam is largely responsible for the identified high level of inundation. The impacts of flood on the local people are devastating as lives and properties have been lost while economic activities reduced due to health risks and mass migration to neighbouring villages and towns. Early flood warning system (EFWS), rapid response mechanism and outfit, strict adherence to zoning and building principles, evacuation of waste and maintenance of drainage systems, mass awareness campaign on flooding and other environmental hazards and, continuous rehabilitation and assistance of victims as a government, individual and NGOs are recommended hence synergy among stake holders is advocated. Keywords: Flood, GIS Buffer, Settlement, Vulnerability, Water Coverage