Extraction, Mapping, and Analysis of Structural Lineaments using Geospatial Azimuth-Altitude Ratio Technique on a DEM of a Sub-Catchment of the Upper Benue River Basin, Nigeria

Abstract

Lineaments have a wide range of implications and applications in geology, hydrogeology and geomorphology. The focus of this study was on structural or geological lineaments and their implication on hydrogeology and hydrogeomorphology. Hence, this study aimed at the extraction, mapping, and analysis of structural lineaments using a DEM in the Adamawa sub-catchment of the Upper Benue River basin. ArcGIS 10.8 was used for the geospatial technique of Azimuth-Altitude ratio (315:45, 200:50, 150:65, and 100:60) variation, manual digitization for the extraction, mapping and analysis of lineaments. The choice of manual or visual digitization was to apply expert experience to extract only structural and exclude geomorphological and pseudo lineaments. The Azimuth-Altitude ratio variation approach was to improve clarity and identification to aid the manual extraction. The lineament map generated after extraction was used to analyze for lineament density, total number, and total length. A further analysis applied the rose diagram to depict the directional orientation or trends of these lineaments. The result revealed that at various Azimuth and Altitude ratios, the features on the image become more distinguishable for extraction. At 315:45 Azimuth and Altitude ratio, the hill-shade produced revealed the major lineaments more clearly compared to other ratios but minor lineaments were undermined. Also, a total number of 343 lineaments were found in the Adamawa sub-catchment of the Upper Benue River Basin with a total length of 2897.81km. The lineament density was found to range between 1km/km2 and 5km/km2. The result of the lineament statistical analysis showed that the extracted lineaments have trends in the direction of N-S, NNE-SSW, NE-SW, E-W, SE-NW, and SSE-NNW. This therefore concluded that the Adamawa sub-catchment of the Upper Benue River Basin has high lineament density and lineament extraction from DEM at various Azimuth and Altitude ratios enhances lineament extraction. The implications of the findings from the results suggest that areas with a high density of lineaments might be affected by higher structural deformation, which signifies higher groundwater infiltration potential zones and initiation of first-order drainage networks. This information is vital for water resources management in the sub-catchment.