Flood Mapping using Geographic Information System: A Case Study of Asokore Mampong Municipal (original) (raw)
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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.
Present Environment and Sustainable Development, 2019
The main objective of the study was to identify high flood risk zones in AMA. The study also used questionnaires to assess local knowledge on what accounts for the high flood risk in their community. Spatial analysis techniques were used to model flood risk based on the following contributory factors; land cover, soil, drainage density, topography and proximity to rivers. The results show that high flood risk areas covered 46.3km 2 (20%), moderate risk area, 72.9km 2 (31.6%), low risk area 41.5km 2 (18%) and very low risk areas, about 6.7km 2 (2.9%). The high flood risk zones were low-lying areas below 50 meters above sea level and closely associated with poor drainage systems. People perceived not just low-lying areas as a paramount reason accounting for flooding but also very bad waste disposal habit of the public. These offsets the efforts of waste management companies to keep drains free of refuse.
AIP Conference …, 2007
Structural growth is a feature of urbanisation. In developing nations, such growth when unplanned may give rise to environmental hazards. Structural growth and the booming economic activities within the floodplain of River Ala in Akure City, Nigeria has induced flooding in this city, with subsequent loss of properties, life and human dis-settlement. The approach in this study is an attempt to describe an important area of application of the geographic information technology in environmental issues in a developing nation. Topographic features were digitised from an existing 1:5,000 topographic map of Akure, with some position data collected and map updated using a handheld GPS. A database was created using both cartographic and attributes data collected from these and other sources. Spatial analyses were carried out using a PC based Integrated Land and Water Information System (ILWIS), version 3.0. The results obtained implicated dumpsites within the river channel as well as structural development within the River Ala floodplain as the major causes of inundation in this section of the city, especially, in the wet season. The study concluded that the use of geoinformation technology, if well implemented, would provide adequate decision support information to planners.
Journal of Geography, Environment and Earth Science International, 2019
Flood has been a serious hazard for the past decades in Nigeria at large. The incidence of 2012 and 2018 flood disaster in Yenagoa, Amassoma and other parts of the state have not been recover till date and the government is not consigned about the well been of the people. The major causes of the flood are attributed to increased rainfall and lack of drainages including dredging of rivers and disobeying of environmental law and infrastructure failure. Coastal Towns or communities are one of the most affected areas of flood and their farms and fishing implements were washed away by the floodwater in 2012 and 2018 in Bayelsa State. Flood management is needed for provision of time information so quick response can be done as soon as possible. Using SRTM data to produce digital elevation model and IDW Contour, the 3D model from ground data of Yenagoa metropolis using ArcGIS 10.6 to generate and analyze them. As a result of field survey, flood level calculation Original Research Article Desmond et al.; JGEESI, 21(1): 1-9, 2019; Article no.JGEESI.48644 2 was made to classified flood hazard zones for migration, Agricultural Educational, and construction purpose such as land suitability. This was used in ascertaining the extent of the flooded area. The result reveals that an area of over 5.9888882km2 and riverine and coastal area is flooded, affecting more than 15 coastal and riverine communities. The finding also concludes that remote sensing data like SRTM data and Geospatial techniques seems effective in mapping and identifying areas prone to flooding. Therefore Remote sensing and Geospatial database should be established for proper flood mapping and the government should constantly dredge the area from time to time.
USING GIS TO MAP AND ANALYZE URBAN FLOODING CHALLENGES IN RUIRU , KIAMBU COUNTY
Ruiru experiences floods during seasons of heavy rainfall. Urban floods in Ruiru are aggravated by the inadequacy of planned mitigation measures by the local authorities. This research mapped the locations that are vulnerable to flooding by making use of geo-processing and spatial analysis tools while identifying the extent of floods in specific location in Ruiru. The study evaluated the adequacy of the current storm water management practices in Ruiru Town and by use of modelling analysis evaluated the locations susceptible to flooding. The study aimed at producing functional results for use by the Physical Planning Department of the Ruiru Municipal Council. The study also established and estimated the number of residents affected by the flood problem. Urban flooding was simulated using one-dimensional hydrodynamic modelling that incorporated data on soil, geology, elevation, Land cover and the drainage systems in the area. Soil data, land cover data, elevation data and natural drainage pattern was collected, rasterized, reclassified and weighted based on an assumed percentage of influence at 30 % for soil, 25% for slope and 45% for land cover. The southern and south western zones of the sub-county were found to be susceptible to flooding. Slope, soil, land cover and in adequacy in storm water drainage facilities are some of the factors contributing to the urban floods in Ruiru. The study found out that about 14.3Km² (27 %) of the total Ruiru Sub-County area of 52.1Km² is likely to experience flooding, ranging from high to moderate possibility of flooding.. About 70% of the residents in the study area are directly or indirectly affected by the urban floods. This was based on the overlay of the susceptibility map and the land use map of the area as well as the distribution of the population. Most of the land that is highly to moderately susceptible to flooding is located in the low lying areas where those who have settled there are vulnerable to flooding. This study illustrated the benefit of using GIS technology in physical planning especially in the management of urban flooding disasters.
Mapping of Flood Prone Areas in Surulere, Lagos, Nigeria: A GIS Approach
Journal of Geographic Information System, 2015
Increase in the frequency of flooding incidents all over the world and indeed in Nigeria is a major cause for concern. The purpose of this research work is to identify the factors that lead to flooding; and using Geographic Information Systems, map the flood prone areas in Surulere. The causal factors of flooding in Surulere, such as high rainfall intensity and duration, land use patterns, human actions, urbanization, soil impermeability to mention but a few were identified. The pattern of rainfall in Surulere was analysed using 20 years rainfall data from The Nigerian Meteorological Agency. The land use/land cover map as well as the DEM of Surulere was generated in the ArcGis environment with ikonos imagery and 1:50,000 toposheet of Lagos S.E which covers Surulere. The Flood prone areas in Surulere were then mapped. Results show that majority of the land area of Surulere is prone to flooding. Flood mitigation such as early warning systems and flood forecasting, proper urban development, awareness and research should be implemented by the Lagos State Government.
Application of Geographic Information System (GIS) towards Flood Management in Calabar, Nigeria
Calabar, the capital city of Cross River State is located on a fan shaped alluvial formation of the Niger delta region, south-south of Nigeria. It is characterized by fast growth in population, economic activities and urbanization, like most coastal cities of the world. The challenges of climate change, rapid land use changes and the fragile geomorphic state of the city were investigated to determine the spatial flooding situation and degree of susceptibility. Geographic Information system was deployed; consequently, sea level rise, increased annual precipitation, and change from pervious vegetated surfaces to impervious concrete surfaces, availability and non-availability of drainage infrastructures were captured and integrated into a common geo-referenced framework (Model). The identified flooding indicator/factors were represented as thematic layers and subsequently simulated to generate flooding susceptibility map. The apparent increase in natural water supply through the swelling ocean, increase in precipitation, expansion of impervious concrete surfaces, about 20% of the city where drainage and waste disposal infrastructures are available and residential structures are well planned, minimal or no flooding is experienced. Floodplains were found to be highly liable to flooding, while areas that are poorly planned with no drainage facilities were found to be highly susceptible to flooding. Digital terrain model (DTM) was developed for the study area. An ideal drainage channel/network for sustainable urban development in the city was thus attempted while other counseling for urban planning were also suggested.
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