Geocarto International

 Journal

 Potential Flood Hazard Zone Mapping Based On Geomorphologic Considerations And Fuzzy Analytical Hierarchy Model In A Data Scarce West African Basin

 Olabanji Aladejana, Ayobami T. Salami, Olusola Olufayo Adetoro

 2019

Fuzzy analytical hierarchy process (FAHP) was employed to map and rank flood hazard zones within the Northwest Benin Owena River Basin (NWBORB). Topographic wetness index, elevation, altitude above channel, slope, drainage density, convergence index, and runoff contributing to water accumulation/stagnation were processed to generate the flood hazard map of the basin. Values for the relative importance of each factor for flood occurrence were obtained using FAHP; these factors were super-imposed using weighted overlay. Sensitivity analysis of the weights was conducted to determine their influence on the overall analysis. The resultant flood hazard map was classified into five zones very high, high, moderate, low, and very low. Sensitivity analysis of the result showed that runoff and slope were the most sensitive factors in the analysis with values of 1.163 and 1.132, respectively. A comparison between flood hazard map and historical floods within the basin established the reliability of the methodology. 

 Sustainable Water Resources Management

 Journal

 Geomorphic, Morphometric And Structural Analysis Of North West Benin Owena River Basin, Nigeria: Implications For Groundwater Development

 Aladejana, O. O., & Fagbohun, B. J.

 2018

An approach detailing geomorphic, morphological and structural characteristics of a basin provides insight into groundwater development in data scarce regions. Remote sensing and GIS aids the identification, extraction and mapping of these characteristics. In this study, the geomorphic, morphological and structural parameters were delineated for North West Benin Owena River Basin (NWBORB), Nigeria towards its groundwater development. The basin was delineated from topographic maps. Five major sub-basins (SB I–V) were generated. Basin geomorphic characteristics were obtained from fundamental topographic information. Each sub-basin was quantitatively assessed of for their geomorphic, morphometric (linear, areal, and relief) and structural aspects. Geomorphic, morphological and structural parameters relevant to groundwater were utilized for sub-basin prioritization and identification of deficit/surplus groundwater zones. NWBORB is a sixth order basin. Dominated by rain fed lower order streams, it reflects late youth to early mature stage of development of the fluvial geomorphic cycle. It has a low stream frequency (Fs) and moderate drainage density (Dd) of 1.149. Bifurcation ratio (Rb) shows that the lower stream orders are surging through highly dissected, steep mountainous terrain that creates a seasonal low groundwater prospect, with exceptions occurring in the pediplains and flood plain areas. A comparison of the predominant orientations of the second, third and fourth stream orders with the lineament directions indicates structural control within the basin. Sustainable water conservation techniques are suggested locally within the drainage basin. SB-II is the most deficit zone, while SB-V is found to be surplus zone of groundwater potential. 

 Journal Of Environmental Management

 Journal

 Hydrological Responses To Land Degradation In The NorthWest Benin Owena River Basin, Nigeria

 Aladejana O.O., Ayobami T. Salami, Olusola Ige Adetoro

 2018

Adequate insights into how land degradation alters the hydrology of river basins will help forecast the hydrological impacts of land cover change dynamics, thereby providing unique information required for sustainable river basin management. This study attempts to utilize a multi-dimensional methodology involving the application of the physically based Soil and Water Assessment Tool (SWAT) hydrological model and Partial Least Square regression (PLSR) statistical model to evaluate the response of the hydrological components within the Northwest Benin Owena River Basin (NWBORB) in Nigeria to land degradation. Using the historic land cover maps of 1986, 2002, and 2015, covering the basin, the SWAT model was employed to simulate the hydrological components for each historic year. The PLSR model was utilized to establish a response relationship between land cover changes and hydrological component modification within the basin. Results showed that between 1986 and 2015, 18.56% of the forest was lost, with a major portion (16.19%) gained by plantation. Consequently, annual water yield and surface runoff increased by 18.28% and 17.26% respectively, while annual base flow and actual evapotranspiration decreased by 22.58% and 21.72% respectively. The reduction in forest is strongly correlated with an increase in plantation (?0.833), surface runoff component (?0.723) and water yield (?0.532). Also, expansion of plantation land is strongly correlated with surface runoff components (0.877) and negatively correlated with base flow component (?0.573). Variable Importance of the Projections (VIP) from the PLSR model showed forest (VIP=1.23), Plantation land (VIP=1.02) as the most important land cover variables altering the basins' local hydrology. The study clearly shows that forest preservation plays an important role in the regulation of water resources within a river basin. This methodology can be replicated for poorly gauged river basins provided the land cover maps and stream discharge data are available. 

 Journal Of African Earth Sciences

 Journal

 Litho-structural Analysis Of Eastern Part Of Ilesha Schist Belt, Southwestern Nigeria

 Fagbohun, B. J., Adeoti, B., & Aladejana, O. O.

 2017

Southwestern Nigeria which is part of the larger West African Shield. The Ilesha schist belt is characterised by metasediment- metavolcanic, migmatite-gneiss and older granite rocks and the occurrence of a Shear zone which has been traced to and correlated with the central Hoggar Neoproterozoic shear zone as part of the Trans-Saharan Belt. Although the area is interesting in terms of geologic-tectonic setting, however, detailed geological assessment and structural interpretation of features in this area is lacking due accessibility problem. For these reasons we applied principal component analysis (PCA) and band ratio (BR) techniques on Landsat 8 OLI data for lithological discrimination while for structural interpretation, filtering techniques of edge enhancement and edge detection was applied on digital elevation model (DEM) acquired by shuttle radar topographic mission (SRTM) sensor. The PCA outperform BR for discrimination between quartzite and granite which are the most exposed rock units in the area. For structural interpretation, DEM was used to generate shaded relief model and edge maps which enable detailed structural interpretation. Geologic fieldwork was further conducted to validate structures and units identified from image processing. Based image interpretation, three deformation events were identified. The first event (D1) which is majorly a ductile deformation produced foliations and folds whose axial planes trend in NNE-SSW. The second event (D2) resulted in reactivation and rotation of the D1 structures particularly the folds in the NE-SW. The third event (D3) produced a transgressive deformation starting with the ductile deformation resulting in the development of sigmoidal structures oriented in NE-SW to E-W direction and the brittle deformation occurring at later stages producing fractures oriented in the E-W to NE-SW directions. These results have important implications in terms of regional tectonics and geological mapping as well as in land-use planning and other areas such as hydrogeology or geotechnics. 

 Global Journal Of Geological Sciences

 Journal

 A PRELIMINARY ASSESSMENT FOR GROUNDWATER IN A PART OF NORTH CENTRAL NIGERIA USING LANDSAT ETM+

 A.Y.B. ANIFOWOSE, O.O. ALADEJANA

 2016

In a basement environment where groundwater is restricted to secondary permeability, structural analysis using remote sensing is a reliable and cheap method for the start-up process for groundwater exploration. In this study, remote sensing and GIS technology were employed as a major tool for groundwater prospecting in a part of North Central Nigeria; an area prone to water scarcity for more than half of every year.

The geological map of the study area, Landsat7 ETM+, and Shuttle Radar Topographic Mission (SRTM) imageries covering the area were employed in this study. Edge enhancements and directional filtering were carried out to enhance the visibility of lineaments on the Landsat imagery. To eliminate bias and subjectivity, Normalized Difference Vegetation Index (NDVI) and Digital Elevation Model (DEM) of the study area were processed for further lineament detection.

Results indicate that lineaments extracted from the Landsat imagery were in agreement with those obtained from the DEM. Those obtained from the NDVI analysis were also in agreement, except for a number of entirely new lineaments detected. This showed the importance of healthy vegetation aligned in a linear or curvilinear way as a major guide to detecting subsurface water-bearing zones that are not visible on the surface. Results also show that the dominant lineaments trend along the NE-SW direction. The northwest and central parts of the study area have relatively high lineament density, while the southern part has very low lineament density. These areas with high lineament density values are more feasible zones for groundwater prospecting.

 

 Materials And Geoenvironment

 Journal

 Integrating Knowledge-based Multi-criteria Evaluation Techniques With GIS For Landfill Site Selection: A Case Study Using AHP

 Fagbohun, B.J.* And Aladejana, O.O.

 2016

A major challenge in most growing urban areas of developing countries, without a pre-existing land use plan is the sustainable and efficient management of solid wastes. Siting a landfill is a complicated task because of several environmental regulations. This challenge gives birth to the need to develop efficient strategies for the selection of proper waste disposal sites in accordance with all existing environmental regulations. This paper presents a knowledge-based multi-criteria decision analysis using GIS for the selection of suitable landfill site in Ado-Ekiti, Nigeria. In order to identify suitable sites for landfill, seven factors – land use/cover, geology, river, soil, slope, lineament and roads – were taken into consideration. Each factor was classified and ranked based on prior knowledge about the area and existing guidelines. Weights for each factor were determined through pair-wise comparison using Saaty’s 9 point scale and AHP. The integration of factors according to their weights using weighted index overlay analysis revealed that 39.23 km2 within the area was suitable to site a landfill. The resulting suitable area was classified as high suitability covering 6.47 km2 (16.49%), moderate suitability 25.48 km2 (64.95%) and low suitability 7.28 km2 (18.56%) based on their overall weights. 

 Modeling Earth Systems And Environment

 Journal

 GIS-based Estimation Of Soil Erosion Rates And Identification Of Critical Areas In Anambra Sub-basin, Nigeria

 Fagbohun, B. J., Anifowose, A. Y., Odeyemi, C., Aladejana, O. O., & Aladeboyeje, A. I.

 2016

Estimation of soil loss through water erosion is an essential exercise which can help decision makers and planners determine the severity of soil loss through rill and sheet erosion and also curtail the development of further gullies in an area already ravaged by gully erosion. While Universal Soil Loss Equation (USLE) is the most commonly adopted model because it provides a straight forward approach for qualitative estimation of soil loss, however its rainfall erosivity component is found incompetent in most parts of the world. To overcome this deficiency, the Revised Universal Soil Loss Equation (RUSLE) was implemented using rainfall erosivity (R) values peculiar to tropical environment of the Anambra area of Nigeria. Rainfall erosivity (R-factor), soil erodibility (K-factor), slope factor (LS-factor), and cover management (C-factor) were generated in GIS environment and then integrated based on RUSLE equation to estimate the rate of soil erosion. The study indicated that about 1804.39 km2 (39.49 %) of the study area have slight erosion rate of 0–10t ha-1 year-1, while the rates of erosion in 746.60 km2 (16.34 %), 1025.38 km2 (22.44 %), 659.55 km2 (14.43 %), 287.08 km2 (6.28 %), and 46.59 km2 (1.02 %) of the study area are 10.6–85.3, 85.4–235.2, 235.3–608,608.1–2200 and 2200.1 t ha-1 year-1 respectively. The study revealed that high rainfall erosivity combined with moderate to high slope factor and decreasing vegetal cover are the major factors driving soil loss in the area. 

 Modeling Earth Systems And Environment

 Journal

 Testing The Ability Of An Empirical Hydrological Model To Verify A Knowledge-based Groundwater Potential Zone Mapping Methodology

 Aladejana, O. O., Anifowose, A. Y. B., & Fagbohun, B. J.

 2016

Groundwater potential characterization is a major component of the developmental strategies required for sustainable management of the water resources of a country. This study explores the potential of Natural Resources Conservation Service (NRCS-CN) estimated runoff/infiltration to verify a knowledge-based groundwater potential zone mapping methodology using remote sensing and GIS. Eight criteria/factors regarded as positive indicators to the existence of groundwater in the study area were mapped and weighted based on the knowledge of the local geology using analytical hierarchy process (AHP). The results from AHP were integrated using Weighted Index Overlay Analysis in a GIS environment to delineate the groundwater potential map of the area. Five classes consisting of very good, good, moderate, fair and poor groundwater potentials, each occupying 4.6, 53.3, 82.22, 37.47, and 0.43 km2, respectively, were delineated. They were found to be in agreement with the borehole information of the area. Curve number (CN) for the various land cover types was generated using the NRCS-CN approach. CN was used to compute a qualitative, terrain-based, runoff/infiltration response for rainfall events in the study area, from which a terrain-based runoff map of the area was computed. A comparison between the groundwater potential map and terrain-based runoff map was done using linear regression analysis. The coefficient of determination (R2) obtained was 0.80. The result indicates a high application efficiency of NRCS-CN method in verifying the accuracy of a GIS-based qualitative groundwater potential mapping 

 GEO OBSERVATEUR Journal Of Moroccan Centre For Remote Sensing, Rabat, Morocco

 Journal

 Evaluation Of Groundwater Potential Of A Basement Complex Environment Using Geoinformation Technology (A Framework For Water Development In Developing Countries)

 .Y.B. Anifowose, O.O Aladejana And O.A Aboyeji

 2015

Groundwater is, no doubt, a resource needed for the sustainable development of any country. Remote sensing and GIS technology have proved to be efficient in the monitoring of earth resources, including groundwater. Akure is a fast-growing city which requires groundwater modelling as a component of its developmental strategy. The hydrogeological factors at play in the study area are considered for this study. Thematic maps of lineaments, land cover, and geomorphology were produced by direct digital image processing of Landsat ETM+ of the study area. Other datasets such as geology, contour, slope, rainfall, and soil, were also obtained from respective thematic maps of the area. The various factors and their intangibles (individual attributes) are assigned weights and reclassified according to their relative importance to groundwater occurrence by using Analytical Hierarchy Process (AHP). The Weighted overlay was subsequently used in modelling the groundwater potential of the study area. Areas with poor, fair, moderate, good and very good groundwater potentials were delineated and their relationships with the various hydrogeological parameters established. The study demonstrated the effectiveness of remote sensing and GIS as a time-saving and cost-effective tool for the delineation and identification of very prolific groundwater potential target areas in a fast-spreading city.